Skeletal System A&P I Unit 6

The skeletal system is divided into what two systems?

appendicular and axial

Appendicular system

126 bones, which consists of the shoulders, hips, and extremities

axial system

80 bones, which consists of the skull, vertebral column, ribs and sternum.

Name the types of bones

long, short, flat, wormian, irregular, sesamoid

long bones

bones that are much longer that they are wide such as the humerus and femur

short bones

cube-shaped bones such as the tarsals and carpals

flat bones

broad thin bones such as the skull bones and scapula

wormian bones

small bones found in the sutures of the skull that are names for teh Danish anatomist, Olaus Wormius

Irregular Bones

Unusually shaped bones such as the vertebrae

Sesamoid bones

small, rounded bones such as the patella

Functions of the bones

1. To physically support the body

2. To protect vital organs found within the body cavities

3. In body movement via the attachment of muscles

4. As a blood forming organ

5. As a storage area for mineral salts such as calcium

Cartilage

is an integral part of the skeletal system

Cartilage functions

1. cushions joints

2. provides smooth surfaces for joints

3. helps support the vertebral column

4. attaches most of the ribs

Types of cartilage

Hyaline, elastic, fibrocartilage,

hyaline cartilage appearance

is the most common type of cartilage and istranslucent, with bluish to pearly tint

hyaline cartilage occurrence

1. Ribs (ventral ends)

2. Long bones (articular ends)

3. Nose, larynx, trachea, bronchi

4. External acoustic meatus

5. Fetal skeleton

Hyaline

most common type of cartilage

Elastic Cartilage

Contains elastic fibers

Elastic Cartilage appearance

yellow and more opaque than hyaline cartilage

Elastic cartilage occurrence

1. external ear

2. Epiglottis

3. Larynx

Fibrocartilage

Contains many collagenous fibers

Fibrocartilage appearance

firm fibrous texture

Fibrocartilage occurrence

1. Intervertebral disks

2. Pubic symphysis

3. Lining of tendon grooves

Perichondrium

is the outer covering of the cartilage and is composed of a fibrous and chondrogenic layer

Fibrous layer

is composed of many collagenous fibers

chondrogenic layer

is composed of loose connective tissue containing many undifferentiated cells (stem cells) retaining the capability of forming chondroblasts and chondrocytes.

Cells and fibers of cartilage

chondroblasts, chondrocytes, fibroblasts

Chondroblasts

are the cartilage forming cells

Chondrocytes

are the mature cartilage maintaining cells

Fibroblasts

are cells that produce the collagenous fibers that are part of cartilage

Vascularity

cartilage is a nonvascular tissue which gets itsoxygen and nutrients from synovial fluid or the perichondriumwhich covers the cartilage in non-articulating areas

Articular Cartilage

approximately 2-4mm thick composed of proteoglycans and merging into a calcified matrix adjacent to the bone that provides compressive strength and adhesion to the underlying bone.

Types of Growth of cartilage

Appositional growth and interstitial growth

Appositional growth

is the process whereby new layers of cartilage are grown or added to the surface of the cartilage

Interstitial growth

is the growth of cartilage by expansion from within. Chondroblasts or dividing chondrocytes produce cartilage from within expanding the cartilage much the way bread dough rises.

Name all 18 parts of a long bone structure?

Diaphysis, epiphysis, periosteum, epiphyseal disk, medullary cavity, endosteum, yellow marrow, red marrow, spongy bone, compact bone, nutrient foramen, nutrient artery, osteocytes, osteoblasts, osteoclasts, lamellae, haversian canal.

Diaphysis

is the shaft of long bones and is made up of mainly compact bone, however the inner layer is composed of spongy bone

Epiphysis

is the articular end of long bones and contains a high proportion of spongy bone

Periosteum

is a dense layer of fibrous tissue which adheres to the outer surface of the bone. It has an outer fibrous layer and inner osteogenic layer

Epiphyseal line

separates the epiphysis and diaphysis in the adult. It identifies the area of growth from birth to adulthood

Epiphyseal disk

is a piece of cartilage which separates the epiphysis from the diaphysis during the growth years

Medullary cavity

is the space within the shaft (diaphysis) that contains yellow marrow in the adult and red marrow in the early growth years

Endosteum

a thin layer of squamous cells that lines the marrow cavity

Yellow marrow

is found in the medullary cavity of long bones and is made up of mainly fat (adipose) tissue

Red marrow

this is the blood cell forming tissue and in the adult it is found in the cranial bones, sternum, ribs, bodies of vertebra, the diploe of cranial bones, the clavicle, the scapula, the Ilium and proximal epiphyses of the femur and humerus

Spongy (cancellous) bone

consists of fine network of bone which contains many spaces filled with red marrow

Compact bone

is dense bone which has few spaces

Nutrient foramen

is a hole in the bone which provides a passageway for blood vessels

Nutrient artery

is the name of the artery that enters the nutrient foramen. It supplies the marrow cavity and inner compact bone

Osteocytes

are mature bone maintaining cells which can no longer divide. Each osteocyte sets in a small cavity known as a lacuna

Osteoblasts

are bone producing cells which produce collagen and mucopolysaccharides

Osteoclasts

are bone destroying cells. These large multinucleated cells are a type of macrophage

Lamellae

are layers of bone cells which are typically arranged in a circular pattern around the central or Haversian canals

Haversian canal

is the central (longitudinal) canal which passes through each Haversian system. It provides a passageway for blood vessels.

Haversian System (osteon)

the circulatory system of bone

Volkmann’s canals

are tunnels (canals) that connect Haversian canals (central canals)

Canaliculi

are tiny canals which connect the lacuna which contains an osteocyte. These little channels provide pathways for oxygen and nutrients to reach all bone cells

Blood Supply to Osteocytes

because of all the interconnecting passageways with the bone most bone cells are no farther than 0.1 mm from a blood capillary

What are the 2 types of development of bone (2 types of ossification)

Intramembranous bone formation and endochondral bone formation

A) Intramembranous Bone Formation

is the replacement of dense connective tissue membranes by bone

A) important terms - mesenchyme

embryonic tissue that gives rise to connective tissues.

A) important terms - trabeculated

loosely woven bone, cancellous bone

Intramembranous sequence of events Step A

Fibrous membrane present

Intramembranous sequence of events Step B

Centrally located stem cells (mesenchymal) differentiate into osteoblasts

Intramembranous sequence of events Step C

Osteoblasts divide and produce osteoid (collagen and mucopolysaccharides)

Intramembranous sequence of events Step D

Calcium moves in and the trapped osteoblasts become osteocytes

Intramembranous sequence of events Step E

The bone grows outward in a random network of trabecular bone.

Intramembranous sequence of events Step F

Vascularized tissue at the surface forms the periosteum.

Intramembranous sequence of events Step G

Trabeculated bone under the periosteum thickens forming loosely woven bone that will be replaced with lamellar (compact) bone.

Intramembranous bone formation occurrence

this type of bone formation is found in some of the bones of the skull and the clavicles. The roof and sidewalls of the cranium and the bones of the face are produced intramembranously, however, the bones in the floor of the cranium are produced endochondrally. The formation of the temporal and sphenoid bones is shared by intramembranous and endochondral bone formation. The result is two layers or plates of compact bone covering an internal layer of spongy bone and marrow called the diploe.

Endochondral Bone Formation Definition

is the process whereby cartilaginous models of future bones are destroyed and replaced by bone

Endochondral Bone Formation Step A

Cartilage model present

Endochondral Bone Formation Step B

stem cells within the perichondrium produce osteoblasts that secrete collagen and proteoglycans (osteoid). Calcification occurs encasing diaphysis in bony collar.

Endochondral Bone Formation Step C

Chondrocytes hypertrophy in the diaphysis (primary ossification center)

Endochondral Bone Formation Step D

enzymes are produced that breaks down the cartilage

Endochondral Bone Formation Step E

Calcium moves in and intercellular substance becomes calcified

Endochondral Bone Formation Step F

Cells die and spaces open up

Endochondral Bone Formation Step G

Periosteal bud with vessels moves in between spaces

Endochondral Bone Formation Step H

Stem cells divide to form osteoblasts

Endochondral Bone Formation Step I

Bone is formed on cartilage remains

Endochondral Bone Formation Step J

Trabeculated bone is the first bone formed

Endochondral Bone Formation Step K

This process of ossification gradually extends in each end of the bone (secondary ossification center)

Endochondral Bone Formation Step L

Under the periosteum bone grows appositionally

Bone Homeostasis growth in length 1

Set between the epiphysis and diaphysis is a disk of cartilage, the

epiphyseal disk

Bone Homeostasis growth in length 2

Cartilage of these disk cells continue to grow and produce cartilage

on the epiphyseal side (3), thus extending the length of the bone

Bone Homeostasis growth in length 3

On the diaphyseal side (4), hypertrophied cartilage cells and

calcified cartilage cells are destroyed by osteoclasts

Bone Homeostasis growth in length 4

Osteoblasts replace the calcified cartilage with bone

Bone Homeostasis growth in length 5

Through the action of the cartilage cells on the epiphyseal side

and osteoblasts on the diaphyseal side, the bone increases in

length

Bone Homeostasis growth in length 6

This action continues until approximately age 16 in females and

18 in males

Maintaining Calcium Levels Glandular Activities 1

The thyroid and parathyroid gland maintain proper blood levels of calcium

Maintaining Calcium Levels Glandular Activities 2

Parathormone (PTH) from the parathyroid gland

increases osteoclastic activity thereby increasing blood

levels

Maintaining Calcium Levels Glandular Activities 3

Calcitonin (CT) from the thyroid gland decrease

osteoclastic activity thereby decreasing blood levels

Calcitonin is available in nasal spray to help prevent bone

loss.

Maintaining Calcium Levels Glandular Activities 4

Growth Hormone (GH) from the pituitary stimulates

general growth in bones. Too little can result in a dwarf

and too much a giant if this imbalance occurs during the

growth years.

Maintaining Calcium Levels Glandular Activities 5

Sex hormones stimulate growth and the quick finish of the

epiphyseal plate. The female hormone, estrogen does this

faster than the male hormone testosterone. As a result,

women are shorter than men.

Rickets

results from a deficiency of Vitamin D which is

necessary for the absorption of calcium from the digestive tract.

Malformations of the head, chest, pelvis and legs may occur

depending on the age of the individual

Osteomalcia (bone softening)

a. due to a lack of vitamin D

b. not enough calcium is not deposited in bone.

c. pain may be felt when stress is put on the bone

Osteoporosis

a. bone reabsorption is greater than bone deposition.

b. caused by low levels of estrogen, lack of exercise, inadequate

intake of vitamin D.

Osteoporosis signs and symptoms

1. spongy bone of the spine is most vulnerable.

2. occurs most often in postmenopausal women.

3. bones become so fragile that stepping off a curb can

cause fractures.

Osteomalcia and osteoporosis treatment

1. calcium and vitamin D supplements as prescribed by a doctor.

2. possible hormone replacement therapy (HRT)

3. increase weight bearing exercise.

Remodeling

reabsorption and deposition of bone, is a process which is controlled by the action of osteoblasts and osteoclasts. It continues throughout life and continually alters the body. For example, as the body ages, facial bones and other bones change their shape and density. Although epiphyseal plates have closed long, bones can remodel such that a small change in height can occur. Exercise, diet and stress can also affect these changes.