(2) Anatomy Notes[1]

8/6/2019 (2) Anatomy Notes[1]

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BSE Notes 2006 L.Lai ANATOMY 1

ANATOMY


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TISSUES & STRUCTURES

KEY PRINCIPLES

Four basic tissue types make up the body epithelium, connective tissue, muscle and nerve.

Epithelium makes up skin, glands, blood vessels, lymphs, etc Connective tissues make up fascia, ligaments, tendon, bones, etc Muscles can be smooth, skeletal or cardiac Nerve is just nerve

EPITHELIUM

The Skin

epidermis and dermis + other structures skin The epidermis ectodermal, made of keratinised stratified squamous epithelium. The dermismesodermal, mainly collagen fibres bundles, elastic tissue, vessels and nerves. b/n epidermis & dermis is where Melanocytes are found in basal layer of epidermis activity determines pigmentationOther structures in the skin

Sweat glands1. Extend into the dermis and subcutaneous tissue.2. Supplied by cholinergic fibres in sympathetic nerves3. Are all over skin except tympanic membranes, lip margins, nipples, inner surface of prepuce, glans penis & labia

minora

Apocrine glands1. Large modified sweat glands2. Confined to axillae, areolae, periumbilical, genital and perianal regions3. Enlarge at puberty and undergo cyclical changes in relation to menstrual cycle

Sebaceous glands1. Open into the side of hair follicles (keeps hair moist)2. Any areas that dont have sweat glands, have sebaceous gland so found on lips, nipples, areolae, inner surface of

prepuce, glans penis and labia minora. Hair

1. Hard keratin formed from the hair matrix, a region of epidermal cells at the base of the hair follicle.2. Melanocytes in the hair matrix impart pigment3. Arrector pili muscles receive sympathetic stimulation and make hair stand on end.

Nails - consists of nail plates lying on nail beds on the dorsum of the terminal segment of fingers and toes. Arteries of the skin are derived from a tangential plexus at the boundary between the subcutaneous and connective tissue. Veins have a similar arrangement. Cutaneous nerves carry afferent somatic fibres and efferent autonomic(sympathetic) fibres. Rule of nines for skin surface area: head 9%, UL 9%, LL 18%, front of thorax and abdomen 18%, back of thorax and

abdomen 18%.

Mucous Membrane

A mucous membrane is the lining of an internal body surface that communicates with the exterior. Consist of epithelium, underlying lamina propria (containing muscularis mucosae in the alimentary tract), which lies on top of

the submucosa.

Serous Membrane

The lining of a closed body pericardial, pleural and peritoneal and consists of connective tissue covered on the surface by asingle layer of flattened mesothelial cells.

Parietal and visceral layers separated by a film of tissue fluid. Parietal layer supplied by spinal nerves, visceral layer possesses no sensory supply.


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CONNECTIVE TISSUE

Fascia

Superficial loose areolar connective tissue, most distinct on lower abdominal wall where it differentiates into 2 layers Deep fascia wrap around muscles for movements, attaches to bones, or between bones (intermuscular septae) supplied

by nerve of overlying skin

Ligaments

condensed connective tissue, mainly collagen, usually attached to bone at their 2 ends. Generally unstretchable unless subjected to prolonged strain.Tendon

Similar to ligaments attaches muscle to bone. May be cylindrical or flattened into aponeuroses.Synovial sheaths

Provide lubrication where tendons bear heavily on adjacent structures Parietal layer firmly fixed to surrounding structures, visceral layer firmly fixed to the tendon, with a thin film of synovial fluid

in b/n.

Cartilage

dense connective tissue, cells embedded in a firm matrix, contains fibres & ground substance mainly proteoglycan, water &dissolved salts.

3 Types of cartilages hyaline, fibrocartilage, & elastico Hyaline cartilage bluish white appearance found on costal, nasal, some laryngeal, tracheobronchial, articular

cartilage of typical synovial joints and epiphyseal growth plates of bones.

o Fibrocartilage contains small islands of cartilage cells + ground substance think of IV discs, labrum of shoulder& hip joints, menisci of knee joints and articular surface of bones which ossify in membranes.

o Elastic cartilage contains a large number of elastic fibres and occurs in the external ear, Eustachian tube and epiglottis. Fibrocartilage has a sparse blood supply, hyaline and elastic cartilages rely on diffusion of substrates through the ground

substance.

BONE

Vascularised dense connective tissue, contains cells embedded in a matrix of collagen fibres, inorganic salts rich in calcium and

phosphate.

2 main types of bone compact & cancellous

Compact bone

Hard, dense, like ivory, on surface cortex of bones, thicker in shafts of long bones & surface plates of flat bones Contains osteocytes embedded in a matrix of collagen fibres arranged in layers contains Haversian systems or osteons Transversely running Volkmanns canals link Haversian canals with each other and the medulla.Cancellous bone

Spongework of trabeculae, inside bones & inside articular ends of long bones No haversian system so osteocytes depend on diffusion from adjacent medullary vessels This is where BM is made in adults, found in ribs, sternum, vertebrae & skull Periosteum

o is a thick layer of fibrous tissue covers bones osteogenic deeper cells differentiate into osteoblasts whenrequired.

o does not cover the articulating surfaces of synovial joints.o Subcutaneous periosteum supplied by nerve of overlying skino Deeper periosteum supplied by nerve from nearby muscles


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The single layered endosteum that lines the inner bone surfaces is also osteogenic. One or two nutrient arteries enter the shaft of a long bone obliquely and divide into ascending and descending branches within

the medullary cavity. Near the ends of bones they join branches from neighbouring systemic vessels and periarticular vasculararcades.

Two main processes of bone development via membranes or via cartilage (see ossification notes)Sesamoid bones

May be fibrous, cartilaginous or bony nodules and are usually associated with certain tendons where they glide over the bone. Their presence is variable, the only constant examples being the patella and the ones in the tendons of adductor policis, flexor

policis brevis and flexor hallucis brevis.

MUSCLE

3 types of muscle skeletal, cardiac and smooth Both skeletal and cardiac muscles are striated whereas smooth muscle is non-striated. Smooth and cardiac muscle fibers have a single nucleus whereas skeletal muscle is multinucleate.Smooth muscle

Parallel, narrow, spindle-shaped cells. Arranged in a longitudinal and circular fashion in tubes that undergo peristalsis. Arranged in whorls and spirals in viscera that undergo mass contraction without peristalsis, eg. Bladder and uterus Impulses are transmitted across nexuses or gap junctions and thus there are fewer autonomic nervesCardiac muscle

Broader, shorter cells that branch. Less powerful than skeletal but more resistant to fatigue Intercalated discs increase the surface area for impulse conduction Cells arranged in whorls and spirals, innervation by autonomic nervesSkeletal muscle

Long cylindrical non-branching fibres Surrounded by endomysium (individual fibers), perimysium (bundles) and epimysium (whole muscle). Orientation of fibres is either parallel (longer range of contraction) or oblique (greater force). Muscles with an oblique disposition may be unipennate, bipennate or multipennate. Muscles may be prime movers, antagonists (relaxing in a controlled manner to assist the prime mover), fixators (stabilizing

one attachment of a muscle so that the other may move), or synergists (preventing unwanted movement).

Arteries and veins usually pierce the muscle with the motor nerve. Lymphatics run back with the arteries to regional lymph nodes. Muscle spindles act as a type of sensory receptor, transmitting back to the CNS information of the state of contraction of the

muscles in which they lie.

Skeletal muscle is supplied by somatic nerves through one or more motor branches which also contain afferent and autonomicfibres.

CN III, IV, VI and VII contain no sensory fibres, rather local branches of CN V convey proprioceptive impulses.

JOINTS

3 types of joints fibrous, cartilaginous & synovial

1. any joints requiring lots of movement synovial2. any joints needs more stability than movement fibrous or cartilaginous


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Fibrous joints

Bone connected to bone by fibrous tissue therefore limited movement 4 places skull sutures, interossesous membranes, interior tibiofibular joint, costotransverse 11 & 12

Cartilaginous joints

Essential bone connected to bone by a cartilage primary or secondary

primary (synchondrosis) when B-C-B think of costochrondal, 1st sternochondral, spheno-occipital secondary (symphysis) B-C-FC-C-B think of midline structures, e.g. pubic symphysis, IV joints

Synovial joints

Characterized by the following 6 thingso Synovial jointsmust have synovial membraneo Its purpose is movement so variable degree ofmovementso Like all joint there are ligamentso 3 more Cs that characterize it cartilage, capsule, cavity

When the cartilage component is hyaline typical joint When its fibrocartilage atypical joint synovial membrane

o lines the capsule and invests all non-articulating surfaces within the jointo secrete a hyaluronic acid lubrication for joint

Interarticular fibrocartilages, discs or menisci are found in joints where the congruity between articular surfaces is low, eg.Knee, sternoclavicular and temporomandibular joints.

Fatty pads are found in some synovial joints, eg. Haversian fat pad of the hip joint.


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BLOOD VESSELS

Capillary walls consist of flattened endothelial cells forming an anastomotic network within most tissues. Arteries consist of three layers:1. Tunica intima endothelial lining, collagenous connective tissue and internal elastic lamina

2. Tunica media elastic connective tissue and smooth muscle in varying amounts.3. Tunica adventitia external elastic lamina surrounded by connective tissue

Veins have the same three layers but have1. a less distinct internal elastic lamina2. much less muscle in the media.3. generally, there are no valve in the veins of the thorax and abdomen.

Anastomoses between arteries are either actual or potential. Potential anastomoses reflect the ability of end arterioles to dilateover time to convey adequate blood.

End arteries are found in spleen, kidney, lung, liver, medullary branches of the CNS, the retina and the straight branches of themesenteric arteries; penis and fingers.

Sinusoids are wide capillaries that have a fenestrated or discontinuous epithelium and are numerous in the liver, spleen,adrenal medulla and bone marrow.

Blood vessels are innervated by efferent autonomic fibres, with constriction mediated by adrenergic sympathetic fibres. Large vessels have their own vasa vasorum.

LYMPHATICS

Lymphatic vessels are simple endothelial tubes. They are different from veins in that they have more valves In general, superficial lymphatics follow veins whereas deep lymphatics follow arteries. Lymph nodes may be bypassed by disease processes so dont necessarily flow in order The thoracic duct may be ligated with no consequence because lymphatics communicate with veins freely in many parts of

body.

LYMPHOID TISSUE

2 ways we fight infection1. via non-specific immune system mainly phagocytosis2. specific immune response require antigen + T & B cells

T cells kill specifically by cell-mediated immune response B cells kill by turning into plasma cells and producing antibodies IgG, A, M, D, E


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Both B & T cells come from the same village(s) BM (or liver & spleen) Once released

1. T cells get educated in the thymus it graduates with 4 degrees Thelper, T killer, T suppressor, & Tmemory it then go and settle in spleen, LNs, & other lymphoid follicles

2. B cells dont go to school they head straight to lymphoid follicles and live there It can form 2 types of cells plasma cells or B memory cells

The lymphoid organs are like store house for these cells they consist of the thymus, lymph nodes and spleen allencapsulated

LNs & spleen contain lymphoid nodule or follicle round collection of lymphocytes with a pale central area germinalcentre

Unencapsulated lymphoid organs mucosa-associated lymphoid tissues (MALT) these include GIT, respiratory,genitourinary tracts, Waldeyers peripharyngeal lymphoid ring of tonsils, Peyers patches so the overlying epitheliumsamples antigens and bring them to the underlying lymphoid tissues

In the thymus no lymphoid aggregations like LNs & spleen instead, spread evenly around cortex medulla has fewerlymphoid tissues, but contain characteristic thymic Hassalls corpuscles these are remnants of the 3rd pharyngeal pouches

from which the thymus developed

The LNs are the only organs with afferent & efferent channels the rest, e.g. thymus, spleen, MALT do not have thesefeatures

Lymphoid follicles of the spleen are found in its white pulp which is scattered in the red pulp that constitutes most of thesubstance of the spleen

In the white pulp T lymphocytes form periarteriolar sheaths some of which are lymphoid follicles with B lymphocytes inthe germinal centres

Apart from lymphocytes all lymphoid organs & organized lymphoid tissue contain macrophages


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NERVOUS SYSTEM

KEY PRINCIPLES

1. Structurally divided into CNS & PNS CNS = brain + spinal cord PNS = cranial nerves + spinal nerves2. CNS & PNS each has 2 functional components of somatic nervous system (SNS) & autonomic nervous system (ANS) Somatic = we have control over, e.g. skeletal muscles (efferent), sensation (afferent) Autonomic = its automatic; e.g. cardiac muscles, smooth muscles & glands

3. group of cell bodies with similar function if in CNS called nuclei if in PNS called ganglia

4. nerve fibres of similar function tend to run together if in CNS called tract if in PNS called nerves

5. nerves fibres may be myelinated or non-myelinated in CNS myelin is formed by oligodendrocytes

a. some nerve fibres are myelinated therefore appear white we call white matterb. some are not myelinated because cell bodies, not tracts therefore darker we call grey matter

in PNS myelin is formed by schwann cells (neurolemmocytes)6. Node of Ranvier exist only b/n myelinated nerve fibres purpose is to greatly enhance conduction velocity7. 2 main types of cells that make up the entire nervous system

Neurons structural & functional unit of the nervous system transmits signals the main actors Neuroglia the support cells of which there are 4 types (see below)

Neurons

Specialized for rapid communication has a cell body, dendrites and axons Dendrites receives electrical signals and carry them towards the body Axons carry efferent signals away from body Myelin = layers of lipid and protein substance, designed for fast conduction Many myelin joined together = myelin sheath, wraps around an axon, like a gladwrap, and greatly enhance conduction

velocity

Neurons communicate with each other via synapses (= point of contact between neurons) by neurotransmitters Neurotransmitter can do many things it can excite, inhibit, continuing or terminating the relay of impulses classic transmitters Ach & NA now include, monoamines, amino acids, nitric oxide, neuropetides

Neuroglia

non-neuronal, non-excitable cells that exist purely to support, insulate and nourish the neurons ~5x more abundant than neurons In the CNS (i.e. brain and spinal cord), there are 4 types of neuroglia

1. Oligodendroglia cells (or oligodendrocytes the schwann cells of CNS)2. Astrocytes3. Ependymal cells4. Microglia (i.e. small neuroglial cells the macrophages of CNS)

In the PNS (i.e. peripheral nerves and cranial nerves), there are 2 types of neuroglia1. Satellite cells hangs around neurons in the spinal ganglia (dorsal root ganglia)2. Neurolemma (i.e. Schwann) cells these form the myelin & neurolemmal sheaths around peripheral nerve fibres

Peripheral nerves1. classified according to conduction velocity which is proportional to their size & function2. are held together by 3 connective issue coverings

Endoneurium sticks individual fibres together Perineurium hold them in a bunch Epineurium wrap these bunches in a single nerve


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3. note that in the sciatic nerve only 20% is nerve, the other 80% is connective tissue4. but in smaller nerves, the proportions are different, obviously more nerve to connective tissues5. need blood supply to survive

sciatic nerve & median nerve have their own blood supply inferior gluteal & anterior interosseous arteries respectively elsewhere supplied by branches from local arteries

6. widest fibres tend to conduct most rapidly7. as a general rule

largest unmyelinated fibres may be motor or proprioceptive smallest, whether myelinated or not, are autonomic or sensory

8. Group A up to 20um, subdivided into A 12-20um, motor & proprioception (Ia & Ib) B 5-12um, touch, pressure & proprioception (II) G 5-12, fusimotor to muscle spindles (II) D 1-15um, touch, pain & temperature (III)

9. Group B up to 3um, myelinated preganglionic autonomic10. Group C up to 2um, unmyelinated postganglionic autonomic, touch & pain (IV)

SPINAL NERVES

1. 31 pairs of spinal nerves 8 cervical, 12 thoracic, 5 lumbar, 5 sacral & 1 coccygeal2. each spinal nerve formed by union ofanterior & posterior root attached to the side of spinal cord by little rootlets in IV

foramen

anterior root contains motor (efferent) fibres for skeletal muscles autonomic fibres from T1 L2 and S2 S4 small amount of unmyelinated afferent pain fibres, relayed from posterior root ganglion

posterior root contains sensory (afferent) fibres cell bodies in the posterior root ganglion (simply a site of cell bodies ,no synapses here)

3. immediately the spinal nerve divides into anterior & posterior ramus anterior rami form plexuses cervical, brachial, lumbar, & sacral posterior rami do not

GENERAL PRINCIPLES OF NERVE SUPPLY

Nerves are faithful; arteries are promiscuousNerves always stay with their origin, e.g. migration of phrenic nerve from C4

Arteries changes with embryology

Motor neuron pools group of nerve cells in brainstem or spinal cord supplying one muscle & overlaps the otherFor example C5,6 supplies deltoid, but also subscapularis


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The only exceptions are trochlear & abducen nerve sole motor SO4, LR6

NERVE SUPPLY OF BODY WALL

1. body wall is supplied segmentally by spinal nerves2. posterior rami pass backwards supply extensor muscles of vertebral column & skull +/- varying extent of overlying skin3. anterior rami supply all other muscles of trunk & limb + skin at the sides and front

Posterior rami

1. each posterior ramus divides into a medial & lateral branch2. both supply muscle, but only one branch, either medial or lateral, reaches the skin

in the upper half of body its the medial branch in the lower half its the lateral

3. C1 has NO cutaneous branch4. posterior rami of C7, 8, L4 & 5 DOES NOT reach the skin5. all 12 thoracics & 5 sacrals reach the skin6. no posterior ramus ever supplies skin or muscle of a limb

Anterior rami

1. supply prevertebral flexor muscles segmentallyby separate branches from each nerve2. form plexuses C5,6,7,8 & T1 form brachial plexus supply upper limb T1-12 + L1 supply muscles of body wall segmentally

each intercostal nerve supplies muscles of its intercostals space the lower 6 pass beyond costal margin to supply muscles of anterior abdominal wall muscles supplied by anterior rami below L1 are no longer in the body wall they have migrated into the lower limb

L1, 2,3,4 form lumbar plexuses L4,5 S1,2,3 form sacral plexuses

NEUROVASCULAR PLANE

1. VAN run together, spiral around thoracic & abdominal wall, in the plane b/n middle & deepest of the 3 layers2. in this neurovascular plane nerve lies below and superficial to artery as they run around the wall3. nerve crosses the artery twice in this path posterioly along the vertebral column and anteriorly near ventral line4. as a general rule

aorta is deeper to skin than spinal cord so artery is always deeper to skin than nerves in this neurovascular plane larger outer nerve circle smaller inner arterial circle

SEGMENTAL INNERVATION OF THE SKIN

Dermatomes1. area of skin supplied by a single spinal nerve2. overlaps considerably hence division of a single ICN does not give rise to anaesthesia on the trunk except at axial linesAxial lines

1. is the junction of 2 dermatomes supplied from discontinuous spinal levels, e.g. C6 & C8 in forearm or C5 & T1 in arm2. in the upperlimb approximately sternal angle to front of limb, almost to wrist3. in lower limb is distorted for 2 reasons

the way the limb of the fetus untwist skin borrowed from trunk


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A practical reason for axial line obvious in spinal analgesia

1. a low spinal anaesthesia anaesthetizes skin of posterior 2/3 of scrotum (which is S3)2. but to anaesthetize an entire scrotum, i.e the anterior 1/3 as well L1 must be involved3. this is 7 levels higher upRegarding dermatomes

1. C1 has NO cutaneous branch2. C2,3,4 supply skin of neck by branches of cervical plexus3. C5,6,7,8,T1 skin of upperlimb via brachial plexuses4. In the trunk skin is supplied in strips from T2 L1 (intercostals nerves each has a lateral & anterior cutaneous branch)5. The lower 6 ICNs (i.e. T7-12) supply skin of abdominal wall

SUMMARY OF DERMATOMES

C1 no skin supplyC2 occipital region, posterior neck & skin over parotid

C3 neck

C4 infraclavicular region (to manubriosternal junction), shoulder & above scapular spine

C5 lateral armC6 lateral forearm & thumb

C7middle fingers

C8 little finger & distal medial forearm

T1 medial arm above & below elbow

T2 medial arm, axilla & thorax

T4/5 nipple

T7 subcostal angle

T8 rib marginT10 umbilicus

T12 lower abdomen, upper buttockL1 suprapubic & inguinal regions, penis, anterior scrotum, upper buttock

L2 anterior thigh, upper buttock

L3 anterior & medial thigh & knee

L4 medial leg, dorsum of foot, medial sole

S1 lateral ankle, lateral side of dorsum & sole

S2 posterior leg, posterior thigh, buttock, penis

S3 sitting area of buttock, posterior scrotum

S4 perianal

S5 & C0 behind anus & over coccyx

SUMMARY OF MYOTOMES

Shoulder

abduct & laterally rotate C5o abductdeltoid, supraspinatus (assist in abduction)o laterally rotate infraspinatus, teres minor

adduct & medially rotate C6,7,8o adduction pec major, lat dorsi, teres major, weak adductors teres minor, coracobrachialiso medial rotation subscapularis, teres major

Elbow

Flexion C5,6o Biceps, brachialiso Brachioradialis


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Extension C7,8o triceps

Forearm

Supinate C6 Pronate C7,8

o Pronator teres, pronator quadratusWrist Extension C6,7

o ECRB, ECU Flex C6,7

o FCR, FCU, (PL)Fingers & thumb

Extension C7,8o ED, EDM

Flexion C7,8o FDS, FDP

Hand intrinsic muscles T1

o LumbricalsHip

flexion (iliacus) = adduction (adductors)L2,3 extension (gluteus maximus) = abduction (glut medius & minimus) L4,5Knee

extension (quads) L3,4 flexion (biceps femoris) L5,1Ankle

dorsiflex (tibialis anterior) L4,5 plantar flex (soleus) S1,2 invert (tibialis posterior) L4 evert (peroneus longus & brevis) L5,1Key summary

C4 diaphragm respiration C5 deltoid abduction of shoulder C6 biceps flexion of elbow & bicep jerk C7 triceps extension of elbow & triceps jerk C8 flexor digitorum profundus & extensor digitorum finger flexion & extension T1 abductor pollicis brevis abduction of thumb T7-12 anterior abdominal wall muscles & abdominal reflexes L1 lowest fibres of IO muscles & transversus abdominis L2 Psoas major, flexion of hip L3 quadriceps femoris extension of knee & knee jerk L4 Tibialis anterior & posterior inversion of foot L5 EHL extension of great toe S1 gastrocnemius plantar flesion of foot & ankle jerk S2 small muscles of foot S3 perineal muscles; bladder (parasympathetic) and anal reflex


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AUTONOMIC NERVOUS SYSTEM

We control skeletal muscles via somatic nervous system

When it comes to cardiac & smooth muscle + gland secretions we rely on autonomic nervous system

Key difference here information is interrupted by a ganglion thus there is a presynaptic & postsynaptic neurons1. presynaptic cells are always in the CNS in lateral horn cells of all thoracic & upper 2 lumbar2. these synapse at ganglia sympathetic trunk information is then relayed via postganglionic fibres to effector organs3. the ganglia for parasympathetic however are different

in the sacral segments ganglia are found in the walls of the effector viscera in the head 4 ganglia exist, so no need for ganglia in visceral wall ?why limited space perhaps

functionally, ANS is divided into sympathetic & parasympathetic

structurally1. Sympathetic is from T1-L22. Parasympathetic from craniosacral outflow

SYMPATHETIC FIBRES

1. every spinal nerve without exception, from C1 to coccygeal carries postganglionic (unmyelinated, grey) sympathetic fibres2. these hitch hike along the nerves & accompany all their branches3. their main function VASOCONSTRICTION purely for temperature regulation4. however, some go to sweat glands in the skin (sudomotor) and to the arrectore pilorum muscle in the hair roots (pilomotor)5. thus, sympathetic system innervates the whole body wall & all 4 limbs6. the visceral branches of the sympathetic system have a different manner of distributionHaving reached a sympathetic trunk ganglion, the incoming preganglionic fibres have 3 options

1. synapse right away, or move up or down and synapse in a different ganglion2. leave the trunk ganglion without synapsing, and pass to a ganglion in an autonomic plexus for synapse3. leave the trunk without synapsing pass to suprarenal gland (+) medulla very few fibres do thisthus cell bodies of postganglionic neurons can be found in 2 places sympathetic trunk or in plexus (e.g. celiac plexus)

General structure of sympathetic trunk

1. 3 in the cervical region C1,2,3,4 fuse together to form superior cervical ganglion C5,6 fuse to formmiddle cervical ganglion C7,8 form inferior cervical ganglion often this again fuses with T1 ganglion forming stellate ganglion (or

cervicothoracic)

2. 11 in thoracic3. 4 lumbar4. 4 sacralfibres from lateral horn cells of each segment of spinal cord leave in the anterior nerve root reaches spinal nerve & itsanterior ramus

the link to sympathetic trunk here is the

rami communicantesthere are 2 types

1. white ramus communicans white because myelinatedmyelinated because it contains preganglionic fibres2. grey ramus communicans grey because not myelinated contains efferent postganglionic fibresthus fibres in grey ramus communicans hitch hike on spinal nerves get off at their stop on blood vessels, sweat glands, etc

Every spinal nerve receives a grey ramus

All the thoracic & upper 2 lumbar nerves have both white & grey rami

Note that because there is no inflow from the cervical region there are no white rami communicantes


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Each sympathetic trunk ganglion has a collateral or visceral branch splachnic nerve in the thoracic, lumbar & sacral regions

But in the cervical region a cardiac branch this goes to cardiac plexus

Visceral branches generally arise high up & descend steeply to form plexuses for the viscera

1. so the 3 cervical ganglia give off cardiac plexus (supplemented by upper thoracic ganglia)2. lower thoracic ganglia 3 splanchnic (greater, lesser & least) nerves pierce the diaphragm reach the celiac plexus3. upper lumbar ganglia lumbar splanchnic nerves descend to the superior hypogastric plexus & then to the left & right

hypogastric (pelvic) plexuses

4. the inferior hypogastric plexuses are joined by visceral branches from all the sacral ganglia (sacral splanchnic nerves)sympathetic visceral plexuses thus formed are joined by parasympathetic nerves

1. vagus to the celiac plexus2. pelvic splanchnics (S2,3,4) to inferior hypogastric plexusesthe mixed visceral plexuses reach the viscera by branches that hitch-hike along the relevant arteries


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SYMPATHETIC SUMMARY

1. sympathetic has 2 components peripheral concerned with vasoconstriction and (+) sweating via peripheral nerves hence thermoregulation central concerned with visceral, gland secretions, peripheral blood vessels etc via splanchic nerves vascular component side branches to adjacent large blood vessels, e.g. ICA, vertebral, aorta, etc

2. white rami communicantes from T1 to L2 nothing above T1 so every sympathetic fibres from C1-8 has to channel viaT1 then up to the cervical ganglia

3. T1 is information overloaded so usually does not control upper limb ANSmainly to do with head & neck4. in sympathectomy to control excessive sweating NEVER remove T1 ganglion can lead to horners syndrome5. likewise for lumbar sympathectomy L1 ganglion MUST NOT be removed otherwise ejaculation may be compromised

PARASYMPATHETICS

Parasympathetic fibres is entirely visceral no distribution trunk or limbs

Most viscera has both sympathetic & parasympathetic innvervation

The only exceptions suprarenal glands & gonads only sympathetic here

Parasympathetic has cranio-sacral distribution

Cranial part preganglionic fibres arise from nuclei in brainstem

1. Accessory (Edinger-Westphal) oculomotor nucleus parasympathetic for CN III2. superior salivary nucleus CN VII3. inferior salivary nucleus CN IX4. dorsal motor nucleus CN Xfibres from CN3, 7, 9 are connected to 4 parasympathetic ganglia in the head

vagus nerve runs solely postganglionic cell bodies in the walls of the viscera supplied, e.g. heart & lungs

Sacral part

1. preganglionic fibres arise from lateral grey horn of S2,3,4 of spinal cord constitute pelvic splanchnic nerves2. they leave the sacral segment go straight to form the inferior hypogastric plexuses3. from here, they run to pelvic viscera & to hindgut, as far up as splenic flexure4. they do this in 2 ways

hitch hiking on blood vessels, or make their own way retroperitoneally then synapse around postganglionic cell bodies in the walls of these viscera

CRANIAL PARASYMPATHETIC GANGLIA

4 ganglia ciliary, pterygopalatine, submandibular & oticEach has 3 inputs & 1 output

The 3 inputs are

1. parasympathetic root carries preganglionic fibres from brainstem nucleus fibres synapse here2. sympathetic root carries postganglionic fibres from superior cervical ganglion, whose preganglionic cell bodies are inlateral grey horn of cord segment T1-3

3. sensory root contains peripheral processes of cell bodies in the trigeminal ganglionthe 1 output branches of distribution carry postganglionic parasympathetic fibres to the effector cells

1. ciliary ganglion ciliary muscle & sphincter pupillae2. pterygopalatine ganglion lacrimal, nasal & palatal glands3. submandibular & otic ganglia to salivary glands


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Ciliary ganglion1. parasympathetic input from Edinger-Westphal part of CN III, via a branch from the nerve to inferior oblique muscle, from

the inferior division of CNIII2. sympathetic input from SCG by branches of the ICA nerve3. sensory input from a branch of the nasociliary nerve with cell bodies in the trigeminal ganglion4. branches short ciliary nerves to the eye thus controlling accommodation & pupil reaction

Pterygopalatine ganglion

1. parasympathetic from superior salivary nucleus by nerve of pterygoid canal & greater petrosal nerve from nervusintermedius part of facial nerve2. sympathetic SCG by ICA nerve, the deep petrosal nerve & nerve of the pterygoid canal3. sensory from a branch of maxillary nerve, with cell bodies in trigeminal ganglion4. branches

to lacrimal gland via zygomatic & lacrimal nerves to mucous glands in the nose, nasopharynx & palate via maxillary nerve branches a few are taste fibres from the palate, running in the greater petrosal nerve with cell bodies in the geniculate ganglion of

the facial nerve

Submandibular ganglion1. parasympathetic from superior salivary ganglion nucleus, via nervus intermedius part of facial nerve & chorda tympani,

joining the lingual nerve

2. sympathetic from SCG by fibres running with the facial artery3. sensory from a branch of lingual nerve, with cell bodies in trigeminal ganglion4. branches to submandibular & sublingual glands via branches of the lingual nerveOtic ganglion1. parasympathetic from inferior salivary nucleus by CNIX & its tympanic branch to the tympanic plexus & then to the lesser

petrosal nerve

2. sympathetic from SCG by fibres running with middle meningeal artery3. sensory from auriculotemporal nerve with cell bodies in the trigeminal ganglion4. branches to parotid gland via filaments of the auriculotemporal nerve5. unlike other 3 ganglia the otic ganglion has an additional somatic motor root from the nerve to the medial pterygoid

the fibres pass through without synapse, to supply the tensor tympani & tensor palate muscles


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EMBRYOLOGY

PHARYNGEAL ARCHES & POUCHES

Mesoderm condensations, side walls form pharyngeal arches

5 of them 1, 2, 3, 4, 6 5th

arch is rudimentary

4 clefts in between these arches

all curve around to the front and meet at midlineopposites the clefts and in between the arches the lining of the pharynx outpouches pharyngeal (branchial) pouchesIn each arch there is

1. skeletal derivatives2. an allocated nerve and muscles it supplies3. an allocated artery4. pouch derivativesremember nerves are always faithful, vascular is promiscuous!

FIRST ARCHMANDIBULAR

Right & left halves of arch fuse ventrally in midlineWhen the mesoderm becomes chrondrified forms Meckels cartilage a template for mandible to form

Skeletal derivative

1. incus2. malleus3. anterior ligament of the malleus4. sphenomandibular ligament fibrous perichondrium of Meckels cartilage5. the lingula at the mandibular foramenNerve mandibular nerve

1. mastication muscles masseter, temporal, pterygoids2. mylohyoid & anterior bell of digastric3. 2 tensor muscles tensor palate & tensor tympaniArtery maxillary artery

First pharyngeal pouch gives rise to

1. auditory (pharyngo-tympanic) tube2. part of the tympanic membrane3. the middle ear4. mastoid antrum5. mucous membrane & glands of anterior 2/3 of tongue

SECOND ARCHHYOID

Skeletal derivatives

1. styloid process2. stylohyoid ligament3. lesser horn & superior part of body of hyoid bone4. stapesNerve facial nerve, supplying

1. muscles of facial expression (including buccinator & platysma)2. stylohyoid3. stapedius


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4. posterior belly of digastricArtery Stapedial artery which DOES NOT persist after birth

The 2nd

pouch forms all supplied by glossopharyngeal nerve

1. part of tympanic membrane2. palatine tonsil3. tonsillar crypts4. supratonsillar fossa

THIRD ARCH

Skeletal1. greater horn of hyoid bone2. inferior part of body of hyoidNerve glossopharyngeal nerve (nerve of third arch) supplies Stylopharyngeus

Artery remains as part of ICA

the 3rd

pouch forms

1. the inferior parathyroid gland2. thymus

FOURTH & SIXTHE ARCHES

Skeletal derivatives are

1. thyroid2. cricoid3. epiglottic4. arytenoids cartilagesNerve laryngeal & pharyngeal branches of vagus nerve which supply

1. intrinsic muscles of larynx2. muscles of pharynx3. levator palateDedicated artery

1. 4th arch on the right SCA on the left arch of aorta

2. 6th arch ventrally connected to the pulmonary trunk dorsally on the left ductus arteriosus dorsally on the right disappear completely this is why the RLN hooks around differently on both sides

Coming from the pouch1. 4th pouch superior parathyroid glands2. 5th pouch ultimobranchial body parafollicular (C) cells of the thyroid glandDerivatives of the L) 6

thpharyngeal arch include

1. ductus arteriosus2. L) RLN


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3. L) pulmonary arteryNote that the L) superior laryngeal nerve is derived form the 4

tharch

BRANCHIAL ARCH ARTERIES

1st

archmaxillary artery

2nd arch stapedial artery DOES NOT persist after birth3

rdarch remains part of the ICA

4th

arch

on the right SCA on the left arch of aorta5

th disappear entirely

6th

arch

ventrally connected to the pulmonary trunk dorsally on the left ductus arteriosus dorsally on the right disappear completely this is why the RLN hooks around differently on both sides

The right RLN loops under the SCA

BECAUSE

On the right side, the 5th

& dorsal part of the 6th

branchial arch arteries degenerate

Derivatives of the left 6th

pharyngeal arch include1. ductus arteriosus2. L) RLN3. L) pulmonary artery

HEART EMBRYOLOGY

Pain sensation in the heart is subserved by the sympathetic system

BECAUSE

The heart is a modified blood vessel

Ductus arteriosus

1. arises from L) 6th branchial arch2. thick muscular wall3. closed off after birth by contraction of its muscular walls4. stimulated to contract into closure due to raised oxygen tension, acting locally5. persists as a fibrous band ligamentum arteriosusDuctus arteriosus closes at birth by muscular contractionBECAUSE

Oxygen tension in the blood perfusing the ductus arteriosus rises when the pulmonary circulation opens up

SEPTUM TRANSVERSUM

A mass of mesoderm lying on the cranial aspect of the coelomic cavity

Its cranial part1. gives rise to pericardium & part of diaphragm2. invaded by cervical myotomes, mainly the 4th producing muscle of the diaphragmCaudal part is invaded by developing liver forms the ventral mesogastrium around the developing liver


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DIAPHRAGM

Origins of muscles fibres & connective tissue of diaphragm are different

Connective tissue comes from 4 sources

Central tendon from Transverse septum Oesophageal & vena caval openings from the oesophageal mesentery Connective tissue around periphery of diaphragm from pleuroperitoneal membranes & mesoderms of the dorsal body wall inability of pleuroperitoneal membrane development is the most common cause of congenital diaphragmatic herniaMuscles derived from muscle cells of 3

rd, 4

th& 5

thcervical myotomes bring its own nerve supply hence phrenic nerve

rootlets

These invade the transverse septum by muscle cells

Muscle cells carry their own nerve supply with them, hence the motor supply from the phrenic nerves

Thus the diaphragm is derived from

1. the transverse septum2. the pleuroperitoneal membrane3. 3rd, 4th & 5th cervical myotomes4. body wall tissuesIn its development, the diaphragm receives contributions form

1. the transverse septum2. 4th cervical myotomes3. pleuro-peritoneal membranes4. transversus layer of body wall musculature

GIT

The ventral mesogastrium

1. has a free border containing the left umbilical vein2. forms the lesser omentum in it thus containing CBD + many other structures that lies b/n the 2 layers of lesser omentumThe ductus venosus

1. connects the left branch of portal vein to the IVC2. carries blood from the L) umbilical vein to the IVC3. short circuits the developing hepatic vasculature4. clots off after birth, when no blood flows through it5. becomes fibrosed called the ligamentum venosum bound the caudate lobe6. it is connected to the ligamentum teresFeatures of the development of the pancreas include

1. fusion of dorsal & ventral outgrowths from the gut2. assymetrical growth of the duodenal wall, bringing the openings of its 2 ducts in line with each other3. drainage of part of the head of pancreas by an accessory pancreatic duct4. an interchange of drainage areas between the 2 ducts through anastomotic channels


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ANATOMY OF THE CHILD

Newborns have different proportions to us

Some structures are fully developed at birth, e.g. the internal ear While others are not, e.g. corticospinal tracts to become myelinated, teeth to eruptKnow that

Neonates are more fully developed in the head than in the tail end

Newborns have no visible neck this gradually changes as the neck elongates and the head become more mobile in terms offlexion/extension and rotation

The abdomen is large & out of proportion reasono cos the liver is massive and pelvis smallo so most of the pelvic organs lie in the abdominal cavity, e.g. ovaries & rectum

but this changes, aso infant grows, pelvic cavity expands, and pelvic organs sink into placeo abdominal wall grows, and eventually the abdomen flattens.

THE SKULL

Key differences larger cranial vaults compared to the face vertical diameter of the orbit = vertical height of maxilla + mandible

o In adult, the vertical diameter of the orbit is only 1/3 that of the height of the maxilla and mandible.o This is because the growth of maxillary sinuses and alveolar bone around the permanent teeth, that basically

elongates the face.

Most of the separate skull and face bones are ossified by the time of birth, but they are fairly mobile and easily disarticulate The skull vaults

o Only compact bone is developed at birtho The cancellous part is yet to develop

Posterior fontanelle closed at 6 months Anterior fontanelle closed at 18 months Frontal bone 2 halves separated by a median metopic suture closed ~7yrsmetopic suture may persist (rare) Fully developed at birth are

o Internal earo Middle earo Mastoid antrum

Mastoid process is absent at birth facial nerve is unprotected at birth, covered only by in fibres of SCM tympanic membrane almost as big as adults, but faces more downwards and less outwards than the adult ear drum mandibular fossa shallow at birth & faces slightly laterally with development, fossa deepens & faces directly forwardThe maxilla

Very limited in height and full of developing teeth Maxillary sinus is a narrow slit excavated into its medial wall Eruption of teeth allows room for excavation of sinus beneath the orbital surface but the maxilla grows slowly until the

permanent teeth begin to erupt at 6yrs

At this time, it grows rapidly. The rapid increase in size of the sinus and the growth of the alveolar bone occur simultaneouslywith increased depth of the mandible

These factors combine to produce a rapid elongation of the faceThe mandible

This is in 2 halves at birth and their cartilaginous anterior ends are separated by fibrous tissue at the symphysis menti Ossification unites the 2 halves in the first year At first the mental foramen lies near its lower border After eruption of the permanent teeth, the foramen lies higher, and is halfway between the upper and lower borders of the bone

in adults


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In the edentulous jaw of the elderly, absorption of the alveolar margin leaves the mental foramen nearer the upper border ofthe mandible.

THE THORAX

Key differences

Thorax more barrel shaped in infants1. Cross section in infant = circular2. Cross section in adults = oval (transverse = 2x AP diameter)

There is a large thymus1. Extends from lower part of neck through the superior into the anterior mediastinum2. Thymus regresses at puberty

The ribs lie more horizontal; thus the cage is set at a higher level than in adult, therefore higher diaphragm level; thereforemore abdominal volume.

the left brachiocephalic vein crosses the trachea above the jugular notch

THE ABDOMEN

Key differences

Large liver1. At birth, this is relatively 2x as big as that in the adult2. Inferior border palpable below costal margin

Kidneys are highly lobulated at birth with very little perinephric fat Suprarenal is enormous at birth, almost as big as the kidneys Caecum is cone shaped and appendix arises from its apex in the fetus pelvic cavity is very small so Fundus of bladder lies above the pubis symphysis even when empty

UPPER & LOWER LIMB

Upper limb

Upper limb more fully developed than lower limb at birth Grasping reflex of the hand is very pronounced Growth in length occurs more at the shoulder and wrist than at the elbowLower limb

Poorly developed at birth; occupies the fetal position of flexion This position is maintained for >6months The lower limb then undergoes extension and medial rotation to prepare for standing and walking This rotation carry the flexor compartment around to the posterior aspect Foot is inverted in the new born, but gradually becomes everted harmoniously with the changes in position of the knee and hip

joints

Growth of the limb proceeds more rapidly at the knee than at the hip or ankle

VERTEBRAL COLUMN

Key differences

Before birth, the column is C-shaped, and concave ventrally (this is due to constriction in utero) After birth, the column is flexible, and therefore can take on any curvature imposed by gravity The cervical curve opens up into a ventral convexity when the infant holds up its head


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The lumbar curve opens up into a ventral convexity when the infant walks (lordosis) The spinal cord ends at L3 at birth; this gradually reduces relatively to L1-2, as the vertebral column extends.

IN SUMMARY

In the new born,

1. the spinal cord ends at L32. the internal ear is fully developed3. Suprarenal is enormous at birth, almost as big as the kidneys4. the appendix arises from the apex of a conical caecum5. the fundus of the bladder lies above the symphysis pubis6. skull vault, cancellous bone is not developed7. the thymus lies in the superior & anterior mediastina8. the left brachiocephalic (innominate) vein may cross the trachea in the neck9. the thorax is nearly circular in cross section10. the normal liver is palpable below the costal margin11. Foot is inverted in the new born, but gradually becomes everted harmoniously with the changes in position of the knee and hip

joints


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OSSIFICATION CENTRES

KEY NOTES

2 ways bones can be formed

1. from membranes intramembraneous ossification here osteoblasts lay down bone in fibrous tissue 3 places to think of skull vault, face and clavicle

2. from cartilage enchrondral ossification a pre-existing hyaline cartilage model gradually destroyed and replaced bybonemost bones, other than the 3 above, are formed in this wayPrimary center of ossification is where bone first appears

Secondary center where bone appears elsewhere after primary center often much later

For long bones1. The primary center of ossification, i.e. most bone first appear in the shaft (diaphysis) ~ 8th intrauterine week.2. secondary ossification, mainly in the epiphyses (ends) centers after birth thus responsible for growth3. The metaphysis overtakes the epiphysis as the cartilaginous gap is bridged and bony fusion occurs.

HUMERUS

1. cartilaginous ossification thus the entire humerus is cartilage until the 8th week2. a primary centre appears in the centre of the shaft at 8th week3. Like most long bones secondary centres appear at both ends4. the upper end has 3 secondary centres

the head during 1st year greater tuberosity at 3 year lesser tuberosity at 5 year these 3 fuse into a single bony epiphysis this is the growing end of the bone fusion occurs with the shaft at 20yrs

5. The lower end has 4 secondary centres capitulum and lateral ridge of the trochlea 2 year medial epicondyle 5 year trochlea 12 year lateral epicondyle 13 year

6. the medial epicondyle remains a separate centre fuses with the shaft at 20yrs7. the other three fuse together into a single epiphysis which fuses with the shaft at 15 yrs

RADIUS

1. cartilage before 8 weeks2. at 8 weeks primary centre appears in middle of shaft3. secondary centres for head & lower end the lower is the growing end (note growing end always distal)

lower end appears at 1 year, and fuses at 20 years the head appears at 4 years, fuses at 15

ULNA

1. cartilage before 8 weeks2. starts ossifying in cartilage at 8th week3. there is a secondary centre for the head, the growing end, which fuses with the shaft at ~18yrs (growing end always distal)4. 2 secondary centres contribute to the development of the olecranon they join the shaft at ~16yrs


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CARPUS

1. all cartilaginous at birth unlike the tarsus2. each carpal bone ossifies from one centre3. capitate the largest bone, ossifies first (first year)4. pisiform the smallest bone, ossifies last (tenth year)5. the others ossify in sequence, according to their size, at approximately yearly intervals6. so roughly one centre appears per year from age 1 to 7, anticlockwise in the R) hand (see below)7. the sequence therefore is

capitate hamate triquetral lunate scaphoid trapezium trapezoid pisiform 1,2,3,4,5,6,7, & 10 the whole carpus, except the sesamoid pisiform bone, is ossified by the seventh year

METACARPALS & PHALANGES

1. primary centres appear by 9th intrauterine week i.e. shafts of all metacarpals & phalanges ossify in utero2. secondary centres appear at 2yrs

all at the bases exception 2, 3, 4, & 5 metacarpals where the epiphysis is at the head

3. all fuse at 20 years4. the tuberosity of each terminal phalanx ossifies in membrane

CLAVICLE

1. first bone to ossify in fetus membranous ossification2. 2 centres, which ossify at the 5th week rapidly fuse


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3. a secondary centre appears at the sternal end during late teens fuses rapidly

SCAPULA

1. ossify in cartilage from several centres2. before 8 weeks cartilaginous3. ossification starts at 8 weeks at the thick part of lateral angle gradually enlarges4. at birth

ossified are the blade and the spine still composed of hyaline cartilage are acromion, coracoid process, medial border and inferior angle

5. secondary centre at the base of the coracoid process ossifies at 10 years fuses, across the glenoid cavity, soon after puberty6. secondary centres appear at about puberty at acromion, coracoid process, medial border, inferior angle, and the lower

margin of the glenoid cavity all fuse by 20yrs

HIP BONES

1. the bone develops in cartilage2. 3 primary centres in the fetus one for each bone, near the acetabulum

ilium weight-bearing, appears first, at 2 month fetal life ischium at 3 month pubis at 4 month

3. At birth acetabulum is entirely cartilage the ilium is a broad blade of bone the ischium and pubis are just tiny bars of bone buried in the cartilage

4. when these 3 bones grow they approximate in a y-shaped cartilage forming the acetabulum5. ischial and pubic rami fuse with each other at about 7 years6. secondary centres begin in the acetabular cartilage at 8 yrs ossification across acetabulum complete by 18yrs7. other centres occur in cartilage around peripheral of the bone these fuse with the main bone by 25yrs

FEMUR

1. except for the clavicle, femur is the first long bone to ossify it does so in cartilage2. a centre in the shaft appears at 7th week of foetal life3. a centre for the lower end appears at birth, its presence is acceptable medicolegal evidence of maturity4. lower epiphysis this is the growing end of the bone, bisects the adductor tubercle unites with the shaft after 20 years5. 3 secondary centres in upper epiphyses


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the head at 1 year of age greater trochanter at 4 years lesser trochanter at12 years these 3 centres fuse with the shaft at ~ 18 years of age

6. note that the NOF is the upper end of the shaft and ossifies as part of it, not from an epiphysis

PATELLA

1. forms in hyaline cartilage2. several centers that appears b/n 3 & 6 yrs they appear as the child start running3. fuse at puberty4. occasionally one centre may not fuse with the main bone, resulting in a bipartite patella, which must not be mistaken for a

fractured patella on an x-ray

TIBIA

1. shaft ossifies in cartilage; primary centre appears in the 8th week of foetal life2.

upper epiphysis

the growing end, shows a centre immediately after birth; joins the shaft at 20 years, along the epiphysealline already noted a secondary centre for the tuberosity may appear about puberty

3. lower epiphysis ossifies at the second year, joins the shaft at 18 years, epiphyseal line passes, a centimetre above the distalend of the shaft includes the medial malleolus it is extracapsular

FIBULA

1. ossifies in cartilage centre in the shaft appears in the eighth week2. epiphysis at each extremity3. head the growing end, ossifies in the fourth year, later than the lower end (in this it is exceptional) fuses with shaft at 20

years

4. lower epiphysis ossifies 1st year joins the shaft at 18yrs

OSSIFICATION OF FOOT BONES

1. all the foot bones ossify in cartilage2. 3 bones of the tarsus ossify at birth calcaneus, talus, cuboid

calcaneus at 3 month talus at 6 month cuboid at 9 month, the presence of this centre is acceptable medicolegal evidence of maturity

3. navicular & cuneiforms ossifies during the first 4 year4. metatarsals and phalanges ossify by shaft centres in utero; their epiphyses are as in the hand

epiphysis of first metatarsal at the base epiphyses of the other 4 metatarsals in the head epiphyses ossify 2 or 3 years later than those in the hand; centres appearing about the fifth year they join earlier than in the hand, ~ 18 years

5. secondary centre on the posterior surface of the calcaneus at ~ 10 year joins at 18 years


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BRAINSTEM & CRANIAL NERVES

BRAINSTEM

1. connects cerebrum & diencephalons above to spinal cord below2. consists of midbrain, pons and medulla oblongata with cerebellum sitting behind, wrapping the back of pons & medulla3. from the torium to C1 vertebra below foramen magnum4.

essentially a highway for up and down nerve fibres5. has a bunch of nucleimainly in 3 broad groups cranial nerve nuclei 3 to 12 the named nuclei, e.g. colliculi, red nucleus, substantia nigra, pontine nuclei & olivary nucleus reticular formation diffuse system of cells & fibres, intermingled with the named nuclei very important

Level of cranial nerve nuclei

1. 3 & 4 in midbrain2. motor of 5, the 6 & 7 in the pons3. 3 sensory nuclei of 5 distributed b/n midbrain, pons, medulla & upper spinal cord4. 8 overlap the junction of pons & medulla, and lie partly in each5. 9 12, in medulla, with 11 having a spinal part derived from cervical region


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MIDBRAIN

1. CN 3 comes out from the front, medial surface, at junction b/n cerebral penducle & pons2. CN4 comes out from the back, curls around the lateral side of the peduncle and passes forward, b/n the 2 arteries, like CN 33. blood supply by PCA & superior cerebellar arteries as they curl around the cerebellar peduncle

PONS

1. the only complete cranial nerve to come out here CN 5 by large sensory and small motor root2. come out laterally from middle of anterior aspect of pons, motor root slightly cranial and medial to sensory root3. the 2 pass forward, together, in the posterior cranial fossa, below tentorium4. basilar artery, may or may not lie in the midline groove5. 6 enter on ventral surface, on the clivus6. 7 & 8 enter more laterally at junction of pons & medulla

MEDULLA OBLONGATA

1. b/n pons above & spinal cord below


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2. extends through foramen magnum to level of atlas3. ventral surface 2 pyramids in front, olives to the side, & inferior cerebellar peduncles, even further4. what comes out of here

6, 7, 8 emerge b/n pons & medullaa. 6 b/n pons & pyramidb. main part of 7 b/n pons & olivec. nervus intermediate part of 7 & 8 b/n pons & inferior cerebellar peduncle

9,10, & cranial part of 11 emerge lateral to the olive 12 b/n pyramid & olive

Blood supply to the medulla

1. anteriorly by branches of vertebral & basilar arteries2. laterally and dorsally by posterior inferior cerebellar artery3. anterior spinal branch of vertebral gives penetrating branches which supply the region next to the midline, i.e. the part

containing the pyramid, medial lemniscus & hypoglossal nucleus damage to these vessels produces medial medullary

syndrome, characterized by

paralysis of tongue on same side hemiplegia with loss of touch & kinaesthetic sense on the opposite side

4. Damage to vessels of the lateral & dorsal part gives rise to the lateral medullary syndrome, characterized by Loss of function of nucleus ambiguous leading to paralysis of vocal cord, palatal & pharyngeal muscles on that side

giving dysphonia & dysphagia

Loss of uncrossed spinal tract of trigeminal & of the crossed spinal lemniscus results in loss of pain & temperaturesensation on the same side of face & opposite side of body


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Horners syndrome on the same side due to interruption of descending hypothalamo-spinal fibres of sympatheticpathway

Involvement of the vestibular nuclei causes vertigo & nystagmus with nausea & vomiting5. Venous drainage

Dorsal aspect to occipital sinus Ventral aspect to basilar plexus of veins and inferior petrosal sinus Medullary vein communicates with the spinal vein

Documents

(2) Anatomy Notes[1]