chapter 12 Flashcards
function of skeletal system x5
- provides a firm framework that gives shape to the body and supports the internal organs.
- Articulation (movement) anchor points for muscle. skeleton determines extent of movement of body parts
- protection of vital organs
- bones act as storage organs for mineral salts and fats (Ca, P, Na, K). distributed via circulatory system when required
- blood cell production. red bone marrow has stem cells that can differentiate into blood cells. which cell is produced depends on the bodily factors
structure of bone x3
- diaphysis: shaft makes up main part of bone. hollow cylinder of compact bone surrounding a cavity. cavity filled with yellow bone marrow which is a fat storage site.
- epiphysis: enlarged ends of bone, covered by articular cartilage. have compact bone on the outside but their central regions contain spongy or cancellous bone (more porous with large spaces filled with marrow-may contain red bone marrow)
- periosteum: dense, white, fibrous cartilage covering on the outside surface of the bone. no periosteum on joints where bone is covered with articular cartilage
microscopic bone structure
bone is classified as connective tissue (cells w matrix)
l-> inorganic salts in matrix increase rigidity, strength and hardness)
single units called osteons/Haversian canals
osteon
centre of each osteon is a central canal around which are lamellae (concentric layers of bony matrix)
between lamellae are small spaces in matrix called lacunae (bone cell occupies each lacunae)
projectuions from each bone cell enter canacliculi (tiny canals)and make contact with adjacent bone cell (materials passed)
central canal contains at least one blood vessel, (or lymph vessel and nerves)
osteon of compact bone
compact bone structure
run parallel to the long axis of the bone giving it maximum strength
lamellae surround Haversian canal
cancellous bone structure
not organised into osteons.
consist of an irregular arrangement of tiny bony plates called trabeculae.
bone cells occupy spaces in trabeculae, but lamellae are not organised in concentric layers and nerves and blood vessels pass through irregular spaces in the matrix
found only in epiphysis region.red bone marrow confined to these cavities
epiphyseal lines of cartilage are remnants of plate seen in young growing bones
bone classification
- shape
- long: femur
- short: carpals/tarsals
- flat: scapula, sternum
- irregular: pelvis
- sesamoid: develop in tendons, patella - structure:
- compact bone: dense, thicker, harder
- spongy/cancellous bone: porous, many large spaces, filled with yellow or red marrow and has network of bony plates (trabeculae)
long bone structure
femur
shaft called diaphysis
medullary cavity filled with yellow bone marrow that stores energy as fat
ends called epiphysis
thin layer of cartilage (articular hyaline cartilage) covers each epiphysis to reduce friction at the joint
hardness of bone
brittle calcified matrix (calcium phospate) increase hardness
while collagen fibres give bone a degree of pliability
osteoblast
young cells that produce bone
forms bone matrix (calcium phosphate and collagen fibres)
osteocyte
formed from osteoblast
mature bone trapped in matrix
maintains bone tissue
osteoclast
reabsorbs/destroys bone tissue
releases acidic enzymes to dissolve bone and make cavities
during growth and healing
active during ageing
Ossification
bone formation and remodelling
bones of skeleton are formed from hyaline cartilage oin embryo by ossification
cartilage x3
- hyaline: closlely packed fine fibres (collagenous) in matrix. chrondocytes seen in lacunae
- strength and flexibility
- rings of trachea and bronchi, end of bones - elastic: elastic and collagen fibres
not so closely packed, flexible/elastic support
- ear cartilage - fibrocartilage: thick collagenous fibres
allows for compression
supports body weight and endures heavy compression
-intercollated discs between vertebrae
- knee joint
- connecting pubic bones
no blood vessels in cartilage
*nutrition and waste removal for cells is through diffusion through matrix-> slow process
chrondocytes have slow metabolism (slow cell division)-> slow healing process
joint
site where two or more bones come together
some are rigid (tightly fit)
some allow bones to move in relation to each other (loosely fit)
types of joints x3
- fibrous:
no movement between bones (fit tightly together)
held in place by fibrous connective tissue
-sutures of skull
hard to break, bone fracture before the joint
2. cartilaginous held in place by cartilage, slight movement -between vertebrae -pubic symphysis - between ribs and sternum
- synovial:
freely movable, movemnt limited by ligaments, tendons muscles and adjoining bones
has s cavity between articular cartilage surfaces of bone, covered with s membrane
types of synovial joints x6
- ball and socket joint
can move in 360º plane (back to forth, side to side, rotation)
- hip, shoulder - hinge joint:
back and forward
-knee, interphalangal, elbow - pivot (trochoid/rotary)
rotation
-vertebrae
-radioulnar in wrists and elbow - gliding
side to side, back to front
-between ribs and vertebrae
-base of thumb - condyloid:
back and forward, lateral (similar to hinge)
-wrist joint
-between phalanges and metacarpals/metatarsals - saddle joint:
back and forward, side to side, some rotation
-thumb
knee joint
articular capsule surrounds and encloses the bone
- the fibrous outer layer capsule (made of dense fibrous connective tissue) attached to the periosteum. Flexibility permits motions and strength avoids dislocatio. hold bones together.
- synovial membrane: makes up inner layer of capsule. loose CT and lots of blood capillaries. lines entire joint except articular cartilage and articular disc
types of movement at joint
flexion (decrease angle between bone) extension (increase angle between bone) abduction (movement away from midline) adduction (movement towards midline) rotation (movement around long axis)
cartilage
within matrix are spaces that contain cartilage cells (chrondoblasts), the produce matrix and gradually become surrounded by it until they are trapped in small spaces called lacunae (chrondocytes)
variation of fibrous structure of cartilage classifies it into three types
synovial fluid
secreted by synovial membrane and fills synovial cavity
lubricates joint and provides nourishment
contains phagocytic cells that remove pathogens
keep surface of bone from touching, small amount that coats
increase fluid means swelling
articular cartilage
covers articulating surfaces of bone forming the joint
smooth surface for movement
articular disc
in knee (meniscus) split cavity in two to direct fluid into areas of greater friction
bursae
little sacs of synovial fluid
prevent friction between bone and ligament/tendon or bone and skin
accessory ligaments
holds the bones together in many joints
osteoporosis
when loss of bone mass with ageing becomes sufficient to impair normal functioning
l-> minor injuries could lead to serious fractures
need to increase calcium intake, vitamin D, exercise and quitting smoking
Osteoarthritis
joint cartilage deteriorates and bone surface is no longer protected
exposed bone begins to wear way and bony spurs/growths may develop from exposed end of bone that forms the joint, the spurs decrease space in joint cavity which restricts the movement
symptoms: pain and stiffness in joints (more severe after pressure applied or exercise), crackling sound when they move
no cure
joint replacement surgery
