Anatomy unit 6 - skeletal system

functions of the skeleton

support - bones of lower limbs support entire body when standing, pelvic girdle supports the abdominal cavity

protection - soft body parts, bones of skull protect brain, rid cage protects heart/lungs

blood cell production - all bones in fetus have red bone marrow which produces blood cells, adults have certain bones that produce them

storage of minerals/fat - bones have matrix that contain calcium phosphate, essential for nerves/muscles to function properly, fat stored in yellow bone marrow

movement - permits flexible body movement, ariculations(joints) occur between all bones

Classification of bones

Long - longer than they are wide

Short - cube shaped

Flat - plate like with broad surfaces

Irregular - varied shapes

Round - circular shape

Anatomy of long bone

- enclosed in tough fibrous connective tissues (periosteum) has continuous ligaments that join bones/tendons that anchor muscles to bones

-end of long bone is the epiphysis (contains spongy bone)

portion between is diaphysis (shaft) isn’t solid but has medullary cavity (Containing yellow marrow) 

Compact bone

osteons made of concentric layers of matrix (lamellae), contains collagen fibers and mineral salts 

-Lacunae contain bone cells (osteocytes), blood vessels and nerves enter central canal 

Spongy bone 

contains bony bars/plates (trabeculae), that follow lines of stress, giving bones strength

-lighter than compact bone but still designed for strength  

Bone growth/repair 

Osteoprogenitor cells - unspecialized cells

Osteoblasts - bone fomring cells

Osteocytes - mature bone cells

Osteoclasts - break down bone 

Ossification (bone growth/dev)

Formation of bone

-intramembranous ossification, bone forms between 2 sheets of fibrous connective tissue (forms skull)

-Endochondral ossification, form most bones of the human body hyaline cartilage models are replaced by bone 

Epiphyseal plate (bone growth/dev)

Band of cartilage in the epipyses of long bones, long bone groth continues until plate is ossified

Appositional growth - increase in bone diameter 

Type of fractures

Complete - bone is broken through

Incomplete - bone isn’t separated into 2 parts

Simple - bone ends don’t pierce the skin 

Compound - skin is torn open by bone 

Fracture repair

Hematoma - w/in 6-8hr after fracturing, blood escapes from ruptured blood vessels and forms a mass of clotted blood in the space between broken bones

Fibrocartilaginous callus - tissue repair begins, fibrocartilage fills the space between the ends of broken bone 

Bony callus - osteoblasts produce trabeculae of spongy bone which convert fibrocartilaginous callus to bony callus that joins broken bones together (lasts 3-4 months) 

Remodeling - osteoblasts build new compact bone at the periphery, osteoclasts reabsorb spongy bone (Creates medullary cavity)

Reduction

repair of a fracture

closed reduction - realigning bone fragments w/o surgery

open reduction - surgical repair of bone using plates,screws,pins 

Bones of Cranium

protects the brain, sutures (immovable joints), composed of 8 bones

-Frontal bone, parietal bones,occipital bone, temporal bones 

Axial Skeleton

Skull, hyoid bone, vertebral column, thoracic cage

Appendicular skeleton

pectoral girdle, upper limbs, pelvic girdle, lower limbs

Vertebral column

supports ribe cage, serves as point of attachment for pelvic girdle, protects spinal cord

has 7 servical (neck), 12 thoracic (chest), 5 lumbar (lower back), 5 sacral, 3-5 coccygeal 

Normal spine curvatures

cervical and lumber - convex anteriorly

throacic and sacral - concave anteriorly 

(provide support and balance) 

Intervertebral disks

prevent vertebrae from grinding against one another, absorb shock, allow motion between vertebrae 

Atlas

supports/balances the head, hs 2 depressions that articulate with occipital condyles allows movement of head (up down) 

Axis

has an odontoid process, projects ring of atlas, when head moves from side to side the atlas pivotes around the odontoid process (side to side) 

Sacrum

5 sacral vertebrae are fused to it,, articulates w/ pelvic girdle and forms posterior wall of pelvic cavity 

Coccyx (tailbone)

last part of vertebral column, formed from fusion of 3-5 vertebrae

Pectoral Girdle

contains 2 clavicles (Collarbone), 2 scapulae (Shoulder blades)

Supports the arms and attaches muscles to move the arm,s the bones are held by ligaments/muscles, allowing flexibility, arm is prone to dislocation at shoulder joint

Pelvic girdle 

contains coxal bones - Ilium, ischium,pubis

Gender differences: female has braoder hips,wider pelvis,inlet/outlet of true pelvis is wider, pelvic cavity is shallow, bones are lighter/thinner

Joint (articulations) classification

Movement - Synarthrosis = immovable, Amphiarthrosis = slightly movable, Diarthrosis = freely moveable

Structure - fibrous, cartilaginous, synovial 

Scapula features

acromion process - articulates with clavicle, provides a place of attachment  for arm/upper back muscles

coracoid process - serves as a place of attachment for arm/chest muscles 

glenoid cavity - arm joints flexibility results of the glenoid cavity being smaller than the head of the humerus 

Fibrous joints

fibrous connective tissue joins bone to bone, immovable

ex. coronal suture between parietal bones and frontal bone

Cartilaginous joints

bones are joined by fibrocartilage/hyaline cartilage, slightly moveable 

ex. ribs are joined to the sternum w/ costal cartilages (hyaline)

Synovial joints

bones don’t touch each other, bones are separated by a joint cavity, usually freely movable 

ex. ligaments composed of dense irregular connective tissue 

Types of synovial joints 

saddle - bone is saddle shaped, fits into complementary regions of the other

ball-and-socket - ball shaped head of one bone fits into cup-shaped socket of another, movement in all planes as well as rotation is possible 

pivot - small cylindrical projection of one bone pivots within the ring formed of bone/ligament of another bone, only rotation is possible 

hinge -convex surface of one bone ariculates with the concave surface of another, up and dow motion in one plane is possible 

gliding - flat of slightly curved surfaces of bones articulate, sliding/twising in various planes is possible 

condyloid  - oval shaped condyle of one bone fits into elliptical cavity of another movement is possible but not rotation 

False pelvis

portion of trunk bounded laterally by ilium, space is much larger

True pelvis

bony ring formed by sacrum, lower ilium, ischium, and pubic bones, has an upper inelt and lower outlet

affects of aging

cartilage and bone gradually deteriorate, chemical nature of cartilage changes and bluish color changes to opauq,chondrocytes die and reabsoption occurs, cartilage goes through calcification becoming hard and brittle

How skeleton maintains homeostasis 

Bones protect the internal organs,assit all phases of respiration, store and release calcium needed by muscular/nervous systems, assist immunity and digestion