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Skeletal SystemGross Anatomy

Chapter 7

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Skeletal System Functions and Components

• Provides framework• Provides levers upon which muscles act to move the body• Protection of organs• Mineral storage• Hemopoiesis• Energy storage• Components

– Bones– Cartilage– Ligaments– Tendons

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Anatomic Bone Features

• Terms– Body: main part– Head: enlarged end– Neck: constriction

between head and body– Margin or border: edge– Angle: bend– Ramus: branch off body– Condyle: smooth rounded

articular surface– Facet: small flattened

articular surface

• Projections– Process: prominent

projection– Tubercle: small rounded

bump– Tuberosity: knob– Trochanter: tuberosities

on proximal femur– Epicondyle: near or

above condyle

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Anatomic Bone Features

• Ridges– Line or linea: low ridge– (Crest or crista:

prominent ridge)– Spine: very high ridge

• Openings– Foramen: hole– Canal or meatus: tunnel– Fissure: cleft– Sinus or labyrinth:

cavity

• Depressions– Fossa: general term

for a depression– Notch: depression in

bone margin– (Fovea: little pit)– Groove or sulcus:

deeper, narrow depression

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Divisions of the Skeleton

• Axial skeleton– Skull– Hyoid bone– Vertebral column– Thoracic (rib) cage

• Appendicular skeleton– Limbs– Girdles

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The Skull or Cranium

• Functions– Protects brain– Supports organs of

special senses– Provides foundation

for structures that take air, food, and water into body

• Superior view of skull– Parietal bones– Frontal bone– Sagittal suture– Coronal suture

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Posterior View of Skull

• Parietal and occipitalbones are major structures

• Lambdoid suture: between parietals and occipital

• (Sutural bones may be present: variable)

• (External occipital protuberance– Ligamentum nuchae:

Helps keep head erect)• (Nuchal lines: Neck

muscle attachment points)

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Lateral View of

Skull

• Parietal bones and squamous part of temporal bone form most of side of skull

• Squamous suture: joins the parietal and temporal bone

• Features of the temporal bone– External auditory meatus– Mastoid Process

– Zygomatic process of the zygomatic arch

• Greater wing of the sphenoid bone anterior to the temporal bone

• Zygomatic bones with its temporal process of the zygomatic arch

• Maxilla• Mandible. Articulates with the temporal

bone.( Body, ramus, condyle, genu, and coronoid process)

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Frontal View of Skull• Major structures are

frontal bone, zygomatic bones, maxillae, and mandible

• Maxilla and Mandible bear teeth

• Orbits. Cone-shaped fossae with their apices oriented posteriorly– (Nasolacrimal canal)– Optic foramen

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(The Orbit)

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Bones of Nasal Cavity

• Nasal cavity. Pear-shaped, open anteriorly

• Nasal septum divided nasal cavity into right and left halves– Bony part is vomer and

perpendicular plate of the ethmoid

– Hyaline cartilage anterior part • Nasal conchae: form lateral

walls– Inferior: separate bones– Middle and superior:

projections of the ethmoid– Increase surface of nasal cavity

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Paranasal Sinuses

• Associated with the bones of the nasal cavity

• Functions– Decrease skull weight– Resonating chambers

• Named for bones in which they are found– Frontal– Maxillary– Ethmoidal– Sphenoidal

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Interior of the Cranial

Cavity

• Cranial cavity: occupied by the brain• (Calvaria (skull cap): upper dome-like

portion of skull)

• Crista galli: prominent ridge in center of anterior fossa. Point of attachment for the dura mater (one of the meninges)

• (Olfactory fossae lateral to crista galli. Olfactory bulb within)– Cribriform plate of the ethmoid forms

floor of olfactory fossae– Olfactory nerves pass through the

foramina of the cribriform plate

• Sella turcica: part of sphenoid bone that houses the pituitary gland

• Foramen magnum: opening where brain attaches to spinal cord

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Inferior View of Skull • Foramina

– Foramen magnum: spinal cord exits and vertebral arteries enter

– (Carotid canals: internal carotid arteries)– (Foramen lacerum: internal carotid )– (Jugular foramen: internal jugular veins)

• Specialized surfaces– Occipital condyles: articulation between

skull and vertebral column– Styloid processes: attachment site for

muscles that move the tongue– (Mandibular fossa: site of articulation with

mandibular condyles)– (Medial and later pterygoid plates: parts

of sphenoid bone that surround posterior opening of nasal cavities)

– Vomer: posterior portion of nasal septum– Hard palate: floor of the nasal cavity. With

the soft palate, separates nasal from oral cavities

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Hyoid Bone• Unpaired

• No direct bony attachment to skull

• Attachment point for some tongue muscles

• Attachment point for neck muscles that elevate larynx during speech and swallowing

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Vertebral Column

• Functions– Supports weight of

head and trunk– Protects the spinal cord– Allows spinal nerves to

exit the spinal cord– Provides site for

muscle attachment– Permits movement of

head and trunk

• Twenty-six bones in adult; 34 in embryo– 5 fuse to form sacrum– 4 or 5 coccygeal fuse to form

the coccyx• Regions

– Cervical (7 vertebrae)– Thoracic (12 vertebrae)– Lumbar (5 vertebrae)– Sacral bone (1)– Coccygeal bone (1)

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Vertebral Column• Four major curvatures in adults

– Cervical: anterior– Thoracic: posterior– Lumbar: anterior– Sacral and coccygeal: posterior

• At birth, column is C shaped– When head is raised, cervical curve

appears– When sitting and walking begin,

lumbar curve develops• Abnormal curvatures

– Lordosis. Exaggeration of lumbar– Kyphosis. Exaggeration of thoracic– Scoliosis. Lateral, often

accompanied by kyphosis

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Intervertebral Disks

• Located between adjacent vertebrae

• Functions– Provide support– Prevent vertebrae rubbing

against each other• Consist of

– Annulus fibrosus: external– Nucleus pulposus: internal and

gelatinous• Becomes compressed with

age and height decreases• With age, more susceptible to

herniation

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General Structure of a Vertebra

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Articulations and Spaces Between Vertebrae

• Articular processes have articular facets where vertebrae meet each other

• Spinal nerves exit the vertebral column through intervertebral foramina

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Cervical Vertebrae

• Superior seven vertebrae• Have very small bodies, tend to have

bifid spinous processes, and have transverse foramina

• Atlas: first cervical vertebra– Articulates with skull and allows

“yes” movement– No body and no spinous process

• Axis: second cervical vertebra– Dens or odontoid process extends

superiorly into the vertebral foramen of the atlas

– Allows rotation of the atlas on the axis, the “no” movement

• Vertebral prominence: most prominent spinous process in area. Usually 7th cervical

• Superior articular facets face superiorly; inferior facets face inferiorly

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Thoracic Vertebrae• Long, thin spinous

processes directed inferiorly

• Long transverse processes• Articular facets on

transverse processes for ribs (first 10 thoracic vertebrae)

• Facets on body for articulation with ribs

• Most ribs have heads that articulate with two sequential vertebrae

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Lumbar Vertebrae

• Large thick bodies• Heavy rectangular

transverse and spinous processes

• Superior articular facets face medially; inferior articular facets face laterally– Adds strength– Limits rotation

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Sacrum and Coccyx• Sacrum

– (Alae: superior lateral parts of fused transverse processes

– Auricular surface: articulates with pelvic bone

– Median sacral crest: partially fused spinous processes

– Sacral hiatus: site of anesthesia injection

– Sacral foramina: intervertebral foramina

– Sacral promontory anterior edge of body of first vertebra. Marks separation of abdominal and pelvic cavities)

• Coccyx: tailbone

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Thoracic or Rib Cage• Functions

– Protects vital organs– Forms semi-rigid chamber for

respiration• Parts

– Thoracic vertebrae– Ribs (12 pair)

• True or Vertebrosternal: superior seven. Attach directly to sternum via costal cartilages

• False: inferior five– Vertebrochondral (3)

joined by common cartilage to sternum

– Floating or vertebral(2) do not attach to sternum

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Appendicular Skeleton• Girdles

– Pectoral or shoulder– Pelvic

• Upper Limbs– Arm– Forearm– Wrist– Hand

• Lower Limbs– Thigh– Leg– Foot

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Pectoral Girdle • Scapula (2)– Acromion process

• Forms protective cover• Attachment for clavicle• Attachment for muscles

– Scapular spine: divides posterior surface into supra- and infraspinous fossae

– Coracoid process: attachment for muscles

– Glenoid cavity: articulates with humerus

• Clavicle (2): articulates with acromion and with manubrium of sternum

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Humerus (Arm)• Head• Neck: anatomic and

surgical• Tubercles: greater and

lesser• Intertubercular groove• Deltoid tuberosity• Capitulum: rounded,

articulates with radius• Trochlea: spool-shaped,

articulates with ulna• Epicondyles

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Forearm: Radius

• Medial: thumb side• Proximal end

– Head rotates in radial notch of ulna.

– Radial tuberosity: site of biceps brachii insertion

• Distal end– Articulates with carpals and

ulna– Styloid process

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Forearm: Ulna

• Lateral: little finger side• Proximal end

– Trochlear notch: fits over trochlea of humerus

– Olecranon process: point of elbow

– Coronoid process

• Distal end– Head articulates with

radius and with carpals– Styloid process

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Wrist and Hand

• Wrist: eight carpal bones– In order from lateral to medial

for proximal row and medial to lateral for distal row: So Long Top Part, Here Comes The Thumb

– Scaphoid, Lunate, Triquetrum, Pisiform, Hamate, Capitate, Trapezoid, Trapezium

– (As a unit are convex posteriorly and concave anteriorly)

– (Carpal tunnel: on anterior surface. Ligament from tubercle of trapezium to hook of hamate)

• Hand: five metacarpals (palm of hand); five digits with their phalanges

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Pelvic Girdle• Coxae and sacrum form

ring• Pelvis: pelvic girdle and

coccyx• Coxae: Right and Left

– Ilium– Ischium– Pubis

• Acetabulum: articulates with head of femur

• Obturator foramen• Sacrum

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Coxae• Formed as fusion of embryonic

ilium, ischium, pubis. All threecontribute to acetabulum

• Ilium: iliac crest, anterior and posterior superior iliac spines, greater sciatic notch, auricular surface, sacroiliac joint, iliac fossa

• Ischium: ischial tuberosity• Pubis ( pubic crest), symphysis

pubis (pubic symphysis)• Pelvic brim

– (False (greater pelvis) pelvis superior to brim

– True pelvis inferior to brim)• Pelvic inlet• Pelvic outlet

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Male and Female Pelvis

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Thigh: Femur and

Patella

• Femur– Head: articulates with

acetabulum– Neck– Trochanters: attachment for

muscles that fasten lower extremity to hip

• Greater and lesser– Distal condyles: articulate with

tibia• Medial and lateral

– Epicondyles: ligament attachment

• Medial and lateral• Patella or kneecap: sesamoid

– In tendon of quadriceps femoris– Changes force relationship

between femur and tibia

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Leg: Tibia and Fibula• Tibia

– Larger and supports most of weight

– Tibial tuberosity: attachment of quadriceps femoris

– Anterior crest: shin– Condyles: medial and lateral;

articulate with condyles of femur

– Intercondylar eminence– Medial malleolus: medial side

of ankle• Fibula

– Articulates with tibia not femur

– Lateral malleolus: lateral wall of ankle

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Foot: Tarsals, Metatarsals, Phalanges

• Tarsals (7)– Proximal row: No

Thanks Cow = Navicular, Talus,Calcaneus

– Distal row: MILC =Medial, Intermediate andLateral Cuneiforms

• Metatarsals (5): foot

• Phalanges: toes

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Arches of the Foot

• Function– Distribute weight of body

between heel and ball of foot: weight transferred from the tibia and fibula to the talus. From there, the weight is distributed first to the calcaneus then through the arch system along the lateral side of the foot to the ball (head of the metatarsals). Footprint in wet sand: only heel, lateral margin, ball, and toes of foot imprinted.

• Three major arches– Transverse arch– Longitudinal arches: Medial

and lateral