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Chapter 7: Skeletal System
Introduction
Functions: Points of attachment, protection, support
Variety of tissue found in bone: Cartilage, dense connective, blood,
nervous # of bones:
Human – 206 Dog – 317 Elephant – 326-351 Rat - 223
Bone Functions
Support softer tissues Gives shape to head, face, thorax, limbs Bones of lower limb, pelvis and backbone
– support body’s weightProtect
Skull – protect eyes, ears, brain Rib cage – protect heart, lungs Pelvic girdle – protect internal
reproductive organs, abdominal organs
Bone Functions
Aid in movement Attachment of muscles Bones and muscles interact to make lever▪ Four components to lever:▪ 1) rigid rod or bar▪ 2) fulcrum or pivot▪ 3) object that is moved against resistance▪ 4) force that supplies energy for movement of bar
Bone Functions
Hematopoiesis Def- production of blood cells▪ Forms: WBCs, RBCs, blood platelets
Occurs in red bone marrow (later in development)▪ Marrow: soft, netlike mass of connective tissue
Inorganic salt storage Most important is calcium▪ Most metabolic processes require calcium (in some
form!) Negative feedback loops keep calcium levels
stable
Visual Bone
Long Bone structure
Diaphysis- shaft of long bone Covered in periosteum
Def – tough, vascular covering of fibrous tissue
Helps form and repair bone tissue Made of compact bone
Tightly packed tissue (no air spaces) Medullary cavity is center
Lined with endosteum (thin layer of cells) Filled with yellow marrow (connective tissue)
Long Bone structure
Epiphysis – either end of long bone Expanded in shape Two types:
Proximal – nearest body Distal – farther away from body
Covered in articular cartilage Made of spongy bone
Contain large air spaces Spaces filled with red marrow
Bone Diagram
Read instructions Use book (pg. 14)
Black paper – background White paper – bones TODAY’s work time:
Draw/Outline person on black paper Proportions/sizes of bones▪ 1st determine height of person
Microscopic Bone
Osteon structure
Concentric circles of calcium carbonate and calcium phosphate matrix surrounding a central canal Central canal- Threaded with blood
vessels and nerves Osteocytes (bone cells)
Found within small spaces in the circles called lacuna
Connected by canaliculus (use these to communicate with nearby cells)
Bone Development
Intro to Bone DevelopmentBegin to form during first few weeks
of prenatal development Most continue to grow and develop into
adulthoodBones form by replacing existing
connective tissues (two ways): 1) Intramembranous bones 2) Endochondral bones
Bone Development
Intramembranous bones Broad, flattened bones Fetal connective tissue
layers form template Osteoblasts starts to
secrete matrix to form the bone▪ Once extracellular matrix
completely surrounds osteoblasts, the cells are called osteocytes!
Bone Development (cont)Endochondral bones
Most bones of skeleton are endochondral Cartilage template made first Primary ossification center begins in
center of diaphysis▪ Cartilage is dissolved and replaced with bone
Secondary ossification centers begin in epiphysis
Epiphyseal plate left between them▪ Bone can grow as long as this plate remains active▪ Once it ossifies, growth is finished
Bone Development (cont)
Bones are continually changed by the action of two cell types: 1) Osteoblasts- secrete calcium matrix
(make bone) 2) Osteoclasts-
dissolve calcium matrix (destroy bone)
Osteoporosis
Bone Diagram
First: Finish proportions and outline QUICKLY!
Then: 1) Drawing bones 2) Finding functions of each bone (use book) 3) Finding which skeleton bones belong to (use
book)Three more work days in class:
1) Today 2) After finish lab on Wednesday (15-20 min) 3) Thurs/Fri: After Bone Quiz (40-50 min)
Organization of Skeleton
Skeletal Organization
Axial skeleton Bones found along trunk Head, neck, vertebral column, thoracic
cage
Appendicular skeleton Bones found in limbs or in attachments
of limbs to trunk Arms, legs, pectoral girdle, pelvic girdle
Skull and Hyoid
Axial skeletonSkull:
Two divisions: 22 bones (total)▪ 1) Cranium (8 bones)▪ Brain case
▪ 2) Facial bones (14 bones)Hyoid:
Located in neck b/t lower jaw and larynx Supports tongue and attachment for
muscles which move tongue during swallowing
Skull
22 bones: firmly interlocked along sutures 8 cranium bones▪ Frontal: above eyes, contain frontal sinuses▪ Parietal (2): behind frontal bone, one on either side
of skull, form bulging sides and roof of cranium▪ Occipital: joins parietal bones, forms back/base of
cranium▪ Temporal (2): each side, joins parietal bones, forms
part of sides/base of cranium▪ Sphenoid: helps form base/sides of cranium,
floor/sides of orbit▪ Ethmoid: part of roof of nasal cavity
Skull
22 bones: firmly interlocked along sutures 14 facial bones▪ Maxillae: forms upper jaw▪ Palatine bones: form hard palate of mouth and nasal
cavity▪ Zygomatic bones: form cheeks and sides of eyes▪ Lacrimal bones: orbit walls▪ Nasal bones: rectangular, lie side by side▪ Vomer bones: thin, flat, form nasal septum▪ Inferior nasal conchae: fragile, scroll-shaped, walls of
nasal cavity▪ Mandible: support chewing muscles, lower teeth
Infant Skull
At birth, skull is incompletely developed Contains fontanels
Def - Membranous, non-hardened portions of skull
Otherwise known as soft-spots Enables infants’ skull to more easily pass
through birth canal Eventually close to form cranial bones
Skull contains: Large orbits, pronounced forehead, small face
Vertebral column
Axial skeleton Otherwise known as backboneConsists of vertebrae separated
by cartilage Sacrum:
Vertebrae fuse to form sacrum (part of pelvis)
Coccyx: Small, rudimentary tailbox (attached to
end of sacrum)
Vertebral column
Three divisions: 1) Cervical ▪ 7 total, make-up bony neck▪ Contain pathways for arteries leading to
brain▪ Few contain forks (for muscle attachment)▪ First: called atlas, support head▪ Second: called axis, provides ability for
head to pivot
Vertebral column
Three divisions: 2) Thoracic▪ 12 total, increase in size as go down▪ Larger than cervical vertebrae▪ Long, pointed portion
3) Lumbar▪ 5 total▪ Located in small of back▪ Adapted to support large weight of
body
Thoracic cage and Ribs
Axial skeleton Protects heart, lungs Parts: 12 pairs of ribs and sternum
Sternum: ribs attach anteriorly True Ribs
First seven rib pairs Connect from vertebrae to sternum
False Ribs Last five pairs Three connect from vertebrae to seventh rib Bottom two only connect to vertebrae (floating)
Pectoral girdle
Appendicular skeleton
Parts: Scapula and clavicle
Connects bones of upper limbs to the axial skeleton
Aids in upper limb movements
Upper Limbs
Appendicular skeletonEach upper limb consists of:
1) Humerus (arm bone) 2) Two forearm bones (radius and ulna) 3) Hand
At distal end of hand: 8 carpal bonds (wrist) 5 metacarpal bones (palm) 14 phalanges (finger)
Pelvic girdle
Appendicular skeleton
Two coxae (hipbones) form girdle Connect the bones of
lower limbs to axial skeleton
Together with sacrum and coccyx, form the pelvis
Lower Limbs
Appendicular skeletonEach lower limb consists of:
1) Femur (thigh bone) 2) Two lower leg bones (tibia and fibula) 3) Foot
Knee joint: patella boneAt distal end of foot:
7 tarsal bones (ankle) 5 metatarsal bones (instep) 14 phalanges (toes)
Bones to know
Bone Terms
Bone Term
Description
Crest Narrow projection
Fontanel Soft spot in skull
Foramen Opening, normally permits blood vessels to pass
Head Enlargement at end
Sinus Cavity within bone
Spine Thorn-like projection
Types of Movement
Adduction vs Abduction Dorsiflexion vs plantar flexion Flexion, Extension, and Hyperextension Supination vs pronation Eversion vs Inversion Protraction vs retraction Elevation vs depression Rotation and circumduction Types of Movement Website
http://www.wisc-online.com/ type in “Movement Terminology” in search box