Skeletal system

5 functions of the skeletal system:

support, protects, movement, storage, blood cell production.

the 2 types of bone

spongy and compact bone

characteristics of spongy bone:

consists of trabeculae, filled w/ red bone marrow, found in ends of long bones, makes up most of short, flat, and irregular bones.

function of spongy bone:

hamatopoiesis in adults (production of blood).

compact bone characteristics:

widely separated cells, surrounded by matrix, forms external covering for all bones, arranged in osteons.

functions of compact bone:

resistance to stress, protection, support.

• the matrix consists of:

15% water, 30% collagen fibers, and 55% mineral salts.

4 types of bone cells:

osteoprogenitor, osteoblasts, osteocytes, osteoclasts.

osteoprogenitor:

bone precursor cells found in endosteum, found w/ in central canals, actively mitotic, some become osteoblasts

osteoblasts

build bone, secrete collagen and organic compounds to build bone tissue and matrix

osteocytes:

mature bone cell, derived from osteoblasts, principle cells of bone tissue, don’t secrete matrix, maintain bone tissue by exchanging waste and minerals.

osteoclasts:

bone dissolving cells, breakdown bone matrix and releases minerals, calcium, important for development and repair of bone, concentrated in endosteum.

long bone characteristics:

longer than it is wide, has a shaft.

long bone functions:

levers for movement

structure of long bones:

epiphysis- end of long bones, either proximal or distal, made of spongy bone, surrounded by thin layer of compact bone.

diaphysis- shaft of long bone, made of compact bone.

metaphysis- where diathesis and epiphyses me an adult bone, epiphyseal plate – where growth plate is, Epiphyseal line – growth plate remnant in adults.

periosteum:

external covering of bone, made of dense, fibrous, connective tissue, has two layers.

Fibrous layer:

outer layer, nutrient layer, lymph, blood vessels, and nerves and bone here.

osteogenic layer:

inner layer, osteoblast form and lay down bone tissue for regeneration, also contain osteoclasts.

Endosteum:

Lines medullary cavity, contains osteoblasts and osteoclasts.

medullary cavity:

Hollow area inside diaphysis, contains yellow marrow in adults, contains red marrow in children, very vascular.

articular cartilage:

A layer of hyaline cartilage, found where two bones come together to form a joint.

nutrient artery:

blood vessel in the medullary cavity.

when does bone development begin and stop?

begins 6th to 7th week of fetal development, stops age 18 for girls and age 21 for boys.

The two types of ossification are:

Intramembranous ossification, endochondral ossification.

Intramembranous ossification:

Formation of bone in or on a fibrous membrane, osteogenic cells become osteoblast to secret matrix become trapped and differentiate into osteocytes, and produce skull bones and clavicle.

Endochondral (intracartilageninous) ossification:

Most bones are formed this way- hyaline cartilage gets replaced by bone.

2 types of bone growth:

interstitial growth (length),

appositional (width)

interstitial bone growth:

add some more bone internally (decreases width of osteonic canals and adds length to bones at epiphyseal plates)

appositional bone growth:

adds more to bone surface, becomes thicker in width

what is bone remodeling?

the replacement of old bone tissue with new bone tissue.

there is reabsorption and bone deposition involved.

bone reabsorption:

removal of minerals and collagen fibers by osteoclasts.

bone deposition:

addition of minerals and collagen fibers by osteoblasts.

what are the benefits of bone remodeling?

Provides bone with continued strength, regulates calcium levels in blood, new bone is more resistant to breaking.

what two factors control bone growth and remodeling?

Calcium levels, gravity (mechanical stress).

how do calcium levels affect bone growth on remodeling?

when calcium levels drop in the blood, it stimulates parathyroid gland to release parathyroid hormone, parathyroid hormone activates osteoclasts, which destroy matrix and release calcium, which increases blood calcium levels until homeostasis.

how does gravity (mechanical stress) affect bone growth?

Stress on skeleton causes bone growth, muscular stress stimulates osteoblast; if you increase muscle mass, then must increase bone mass and bone becomes thicker, exercise increases calcitonin, which inhibits osteoclasts and bone absorption, lack of stress weakens bones through demineralization and collagen reduction.

how does aging affect bone?

loss of bone mass due to demineralization

brittleness due to decrease in ability to make organic part of matrix mainly collagen fibers – bone loses tensile strength, and flexibility, makes it brittle and easy to break.

where is bone marrow found?

found in spongy bone and medullary cavities.

Red bone marrow:

in medullary cavities of bones in children, in red marrow cavities of the epiphyses of long bones in adults, and in medullary cavity it is replaced by yellow marrow in adults.

function of red bone marrow:

Hematopoiesis – produces blood cells.

yellow marrow:

found in medullary cavities of adult bones.

function of yellow marrow:

to store adipose tissue, which stores triglyceride.

what does the appendicular skeleton contain?

Bones of the appendages.

what does the axial skeleton contain?

Bones of the long axis of body: skull and spinal cord

what are fontanels?

Soft spot in babies skull, fibrous connective tissue that undergoes intramembranous ossification and becomes bone 22 to 24 months after birth.

what are the two important functions of fontanels?

They allow head to compress as it goes through birth canal, and allow for rapid growth of brain.

what are the four major sinuses?

Spheniod sinus

Ethmoid sinus

Frontal sinus

Maxillary sinus.

what are the purpose of sinuses?

The lighten the skull and voice quality, they connect with nasal cavity and they are filled with air.

Open/compound fracture:

Bone protrudes through skin.

Close/simple fracture:

Bone doesn’t protrude through a skin.

comminuted fracture:

bone is broken into three or more pieces, this is the most difficult to treat.

Greenstick fracture:

Bone is broken on one side and bent on the other, only occurs in children.

impacted fracture:

End of fractured bone is driven into another bone.

pott’s fracture:

Fracture at the distal end of the fibula, common sports injury

colles fracture:

fracture at distal end of radius, common in osteoporosis.

stress fracture:

Microscopic fissures(breaks) in the bone.

what are the four steps of bone repair?

hematoma forms

fibrous cartilage forms

bony callus forms

bone remodeling

osteoporosis:

most common bone disease,

bone reabsorption outpaces bone formation,

Fractures of hip wrist and vertebrae are common,

Affects mostly elderly 80% a woman,

risk factors of osteoporosis:

age, sex, race, menopause, weight, poor diet, lack of vitamin D, smoking, use of glucocorticoids.

cleft palette/cleft lip:

when palatine process of maxillary bones do not unite, speech and swallowing can be affected, makes it hard for infant to nurse.

herniated disc:

intervertebral discs slips out of place and exerts pressure on spinal nerves, causing pain.

scoliosis:

Most common abnormal curve of vertebrae column, vertebral column bending in thoracic region, causes poor posture, shorter leg and back pain.

kyphosis:

exaggeration of thoracic curve In vertebral column, can be caused by osteoporosis, weightlifting, wrestling, crickets, poor calcification of matrix due to vitamin D deficiency, poor posture.

lordosis:

Exaggeration of lumbar curve of vertebral column, caused by added weight due to pregnancy or obesity, poor posture, rickets, osteoporosis.

spina bifida:

congenital defect of vertebral column, laminate of L5 and/or S1 don’t completely develop, in some cases, spinal cord and meninges protrude through the defect, can either have no symptoms or can have neurological problems, such as paralysis, loss of urinary and bowel control.

forward head posture:

newer syndrome, also known as texting neck, computer, neck, readers, neck, and others. Increases pressure on cervical spine, causing neck and shoulder pain. Head feels 10 pounds heavier to neck muscles for every inch the head moves past the shoulders.

The appendicular skeleton specifically consist of:

pectoral, girdle, upper extremities (arms, wrists, hands, fingers), Pelvic girdle and lower extremities(Legs, ankles, feet, toes).

pectoral girdle – 4 bones:

scapula – 2

Clavicle – 2

upper extremity – 60 bones

Humerus – 2

Radius – 2

ulna – 2

Carpals – 16

Metacarpals – 10

Phalanges – 28

pelvic girdle – 2 bones

coxal bone-2 (Each made up of ilium, ischium, and pubis)

lower extremities – 60 bones

femur– 2

Tibia –2

Fibula –2

Patella –2

Tarsals –14

Metatarsals – 10

Phalanges – 28

axial skeleton :

consists of skull, hyoid, Ear bones, thorax(Ribs and sternum), Vertebrae

skull-22 bones:

8 cranial bones

frontal-1

parietal-2

occipital-1

temporal-2

sphenoid-1

ethmoid-1

14 facial bones

maxilla-2

palatine-2

zygomatic-2

lacrimal-2

nasal-2

inferior nasal concha-2

vomer-1

mandible-1

middle ear ossicles:

incus, malleus, stapes

hyoid bone:

only 1, doesn’t articulate w any other bone

vertebral column:

cervical-7

thoracic-12

lumbar-5

sacrum-1

coccyx-1

thorax-25 bones

ribs-24

sternum-1

how many total bones in the body are there?

206 bones