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