SKELETAL SYSTEM

functions of the skeletal system

supports the body, gives shape to the body, protects internal organs, helps make movements possible, stores calcium and hematopoiesis

hematopoiesis

blood cell formation in red bone marrow

long bones

greater length than width, slightly curved for strength.

mostly compact bone but also have spongy bone. vary greatly in size.

e.g. femur, tibia, fibula, radius, ulna, phalanges

short bones

cube-shaped, almost equal in length & width.

mostly spongy bone but surface has thin layer of compact bone.

e.g. carpals, tarsals, patella

flat bones

thin bones consisting of two almost parallel plates of compact bone.

sponngy bone layer sandwiched between two compact bone layers.

protection for muscle attatchment.

e.g. crainial bones (protect brain), ribs & sternum (protect thorax), scapula (shoulder blades)

irregular bones

complex shapes, cannot be put into any other category.

vary in amount of spongy and compact bone present.

e.g. vertebrae (backbone), hip bones, certain facial bones

sesamoid bone

small rounded bones, found in joints.

develop in certain tendons where there is friction, tension and stress.

protect tendons from excess wear and tear.

e.g. palms of your hands, soles of your feet, patella

diaphysis

or shaft

hallow tube of hard compact bone

medullary cavity

hollow area inside diaphysis bone that contains YELLOW BONE MARROW

epiphyses

or ends of the bone

spongy bone that contains RED BONE MARROW

articular cartilage

covers epiphyses and functions as a cushion

periosteum

strong membrane covering bone everywhere except at joint surfaces

endosteum

membrane lining medullary cavity

diploe

spongy bone layer of a flat bone

spongy

or cancellous

texture results from trabeculae surrounded by a network of open spaces.

found in epiphyses of bones, spaces contain RED BONE MARROW.

trabeculae

needlelike threads of bone

compact

structural unit is an osteon: calcified matrix arranged in concentric lamella

osteocytes are found inside lacunae which are connected by canaliculi

concentric lamella

multiple layers or rings of calcified bone matrix

osteocytes

mature bone cells

they maintain and monitor the protein and mineral content of the surrounding matrix.

each of these directs both the release of calcium from bone to blood and the deposition of calcium salts in the surrounding matrix.

inactive osteoblasts

lacunae

spaces in the calcified bone matrix

canaliculi

tiny tubes that connect lacunae to each other

osteons

each of these consists of a single haversian canal surrounded by concentric layers of calcified bone matrix

Haversian canals

or central canal

allow the passage of blood vessels, lymphatic vessels, and nerve fibers.

lamella

each of the concentric matrix ‘tubes’ that surrounds a haversian canal

bone and cartilage

are two specialized forms of connective tissues which are composed of cells embedded within an extracellular matrix

chondrocytes

are the mature cells of cartilage tissue

matrix

is gel-like and lacks blood vessels

osteoblasts

immature and active cells

these produce osteoid

osteogenesis is done here

form new bone

osteoid

organic component of the bone matrix

osteogenesis

process of making new bone

osteoprogenitor cells

divide and differentiate to form new osteoblasts

osteoclasts

these are giant multinucleated cells

perform osteolysis

reabsorb bone

early bone development

before birth

consists of cartilage and fibrous structures

endochondral ossification

process in which temporary cartilage models are gradually replaced by calcified bone matrix.

replacement of hyaline cartilage with bone.

Intramembranous ossification

development of bone from a fibrous membrane

Before week 8

the human embryonic skeleton is made of fibrous membranes and hyaline cartilage happens during _______.

After week 8

bone tissue begins to replace the fibrous membranes and hyaline cartilage happens during _______.

Young

Bone growth occurs when osteoblasts are creating more bone matrix than osteoclasts are removing.

Young adults

osteoblast activity and osteoclast activity are in balance, and the rate of bone formation is equal to the rate of bone reabsorption.

Older individuals

osteoblasts activity decreases faster than osteoclast activity. As a result bone resorption exceeds bone deposition, and the skeleton gradually gets weaker and weaker.

Normal bone growth and maintenance

or maintenance cannot occur without sufficient dietary intake of calcium and phosphate salts.

Calcitriol

A hormone required for the absorption of calcium and phosphate in the intestine

Calcium and phosphate

essential mineral salts required on sufficient dietary intake for normal bone growth and maintenance

Cholecalciferol

or vitamin D is a steroid synthesized in the skin or obtained from the diet that is required for the synthesis of calcitriol

Vitamin C, A, K, and B12

these are necessary for bone growth

Axial skeleton

• includes 80 bones

• consists of skull, spine, thorax, hyoid bone, ribs, sternum

Appendicular skeleton

• includes 126 bones

• consists of the upper extremities, including shoulder (pectoral) girdle

• consists of the lower extremities, including hip (pelvic) girdle

Cranium

8 bones

Face

14 bones

middle ear

6 tiny bones

Air-filled sinuses

are necessary to make the skull light enough for the neck to hold the head upright.

Sutures

Two parietal bones form immovable joints called _____

Hyoid bone

this is found in the anterior of the neck, between the mandible and the larynx

suspended by ligaments and muscles

supports the tongue

thorax

entire chest cavity

Thoracic cage

skeletal part if the thorax

Structure of thoracic cage

it is the bony enclosure made up of the sternum, costal cartilage, ribs and bodies of the thoracic vertebrae

Function of thoracic cage

it protects the thoracic & superior abdominal cavities & supports the bones of the shoulder girdle and upper limbs

Rib pairs 1 - 7

are attached to the sternum by costal cartilage (true ribs)

Rib pairs 8 - 10

are attached to the cartilage of the seventh pair (false ribs)

Rib pairs 11 - 12

are not attached to any costal cartilage (floating ribs)

Vertebrae

protect the spinal cord

Cervical

7 vertebrae

thoracic

12 vertebrae

Lumbar

5 vertebrae

Sacrum

5 vertebrae

Coccyx

1 vertebrae

Girdle

bones are those which connect the upper and lower extremities (limbs) to the axial skeletal

two types are pectoral and pelvic

Pectoral girdle

attaches arm bones to axial skeleton

includes clavicle (collarbone), scapula (shoulder blade)

Upper limbs

or arms

main function is movement

Pelvic girdle

attaches leg bones to axial skeleton

includes 3 fused bones that make the Os coxa or coxal bone

Male skeleton

is generally larger

Male pelvis

Deep and narrow

Female pelvis

Broad and shallow

Female pelvic inlet

generally wider, normally large enough for baby’s head to pass through it

Pubic angle

Angle between pubic bones of female generally wider

Lower limbs

or legs

main function is movement

Age 25

human skeleton reaches its mature state

After age 50

the density of bone often decreases slowly

Environmental factors

Without enough calcium or vitamin D, the skeleton may show signs of degeneration

Exercise has a profound effect on the skeleton

Joints

also known as articulations

hold our bones together and make it possible for movement to occur

• Every bone except the hyoid (which anchors the tongue) connects to at least one other bone

• defined as the place where 2 OR MORE BONES ATTACH TO EACH OTHER e.g. knee, elbow, vertebrae

• classified according to their AMOUNT AND TYPE OF MOVEMENT

Tendon

is a fibrous connective tissue which attaches muscle to bone. A ______ serves to move the bone or structure.

Ligament

is a fibrous connective tissue which attaches bone to bone, and usually serves to hold structures together and keep them stable.

Diarthroses

Free movement

Synarthroses

No movement

Amphiarthroses

Slight movement