Human A & P

Bone Structure and Function

I. Introduction to The Skeletal System A. Background information about the skeletal

system:1. The skeletal system includes the entire framework of ____________ and

their _____________.

2. Each bone is considered to be an ___________.

BonesCartilage

organ

3. Bone tissue is a __________________ tissue. a. The _______________ is:

i. _________________________ - to

provide hardnessii. ______________ - to provide

some flexibility.

iii. _____________

connectivematrixCrystallized Minerals

Collagen fibers

Water

b. The ______ kinds of cells of bone tissue and their functions:

i. ________________ - bone building cells which produce the matrix. (modified fibroblasts). This process is called _________________________.ii. ________________- matured bone cells that develop from osteoblasts, which help to maintain bone _________________. (take in nutrients and release wastes).

3

Osteoblasts

Osteocytes

metabolism

Bone formation

iii. ______________________- (modified macrophage) huge cells made from 50+ WBCs that produce lysosomal enzymes & acids to break down bone matrix. This is a process called __________________.

Osteoclasts

resorption

II. Gross Anatomy of BoneA. Classification of bones based on shape

1. _______________- greater in length than in width. Ex –

2. _______________- nearly equal in length and width Ex -

Long Bone

Femur, tibia, ulna, humerus, phalanges

Short Bone

Wrist, & ankle bones

3. ________________ - thin and flat Ex –

4. _________________- complex shapes that do not fit other categories.Ex -

Flat BoneRibs, cranium, sternum, shoulder blades

Irregular Bone

Vertebra, pelvis, some facial bones

B. Macroscopic Structure of Bone1. gross view of outside of bone

_____________________- end of boneepiphysis

_____________________- end of boneepiphysis

_____________________- main middle portion of the bone.

Diaphysis

_______________ - region in mature bone where diaphysis meets epiphysismetaphysis

Metaphysis

_____________________- thin layer of cartilage over the epiphysis where the bone connects with another bone. It has two features:

1. ________________ & protects the ends of bone.2. _________________ability to repair itself. Why????

Articular Cartilage

cushions

limited

Articular Cartilage

2. gross view of the inside of the bone

_____________________- a layer of cartilage in growing bone where the diaphysis can grow in __________.

- when the bone stops growing in length, bone will replace the cartilage and become the _____________________________.

Epiphyseal Plate

LENGTH

Epiphyseal Line

Site of _______________________ in babies and adults which is where blood cell production occurs.

Red bone marrow

_____________________- looks like a network of bone with marrow in between.

Spongy Bone

_____________________- single layer of bone-forming cells membrane that lines the inside of the medullary cavity.

Endosteum

_____________________- dense bone that serves to protect and support.

Compact Bone

_____________________- dense irregular connective tissue that surrounds bone where articular cartilage is absent. Serves the following functions:

1.____________ the bone & assists in fracture repair. 2. ____________ point for ligaments & tendons.3. _____________ & thickens the bone. BUT DOES NOT LENGTHEN!4. _______________ bone tissue.

ACRONYM HELP – P.A.W.N.

Periosteum

Protects

Attachment

Widens

Nourishes

_____________________- contains __________________ in babies, but as we age, this marrow becomes __________________ as adults which acts as fat storage.

Medullary CavityRed bone marrow

Yellow bone marrow

_____________________- transports nutrients and waste into & out of bone. (This is how breaking one’s “femur” could be a life-threatening, blood loss situation).

Nutrient Artery

III. Microanatomy of Compact and Spongy Bone

A. Anatomy of both types of bones.1. Compact bone ___________________- units

that compact bone are arranged in. (also called ____________.)

Haversian System

osteons

Circumferential Lamellae

Blood vessels

___________________- rings of hard, calcified matrix around the Haversian canal.

Concentric LamellaeCircumferential Lamellae

Blood vessels

Circumferential Lamellae

Blood vessels

_________________- central canal in the osteon that contains: ___________________________________.

Haversian Canal

Nerves, lymph & blood vessels

Circumferential Lamellae

Circumferential Lamellae

Blood vessels

_________________- Leads to the periosteum

Perforating Canal

Circumferential Lamellae

Concentric Lamellae

Compact Bone (continued)

______________- the bone cell.Osteocyte

______________- (“small lake”) – small space that holds the osteocyte.

Lacunae

__________________- small channels filled with extracellular fluid which connects lacunae w/ each other and Haversian canal

Canaliculi

Haversian Canal

Red Space for ___________ bone marrow.

2. Spongy Bone

_______________- a network of thin columns of bone.

Trabeculae

Lacuna

Concentric Lamellae

Canaliculi

____________- fiber makersOsteoblasts

_______________- microbe killersOsteoclasts

____________- bone “maintainers”

Osteocyte

B. Differences between compact and spongy bone:

1. anatomical differences of each type:a. __________________ with Haversian canals are unique to compact bone.

b. ___________________ are unique

to spongy bone.

Osteons

Trabeculae

2. Location of each type in the body:

a. COMPACT bone is found in the ________________ of long bones.

b. SPONGY bone is found in:i. the _______________ and near the _____________________ of long bone.ii. Makes up most of: ___________ __________________________.

Diaphysis

epiphysisMedullary cavity

flat, short & irregular

3. Density differences of each type:a. Spongy bone is _______________

with empty spaces in between for red bone marrow to fill.

b. Compact bone is ____________ packed

with few spaces in between cells & ___________.

lighter

tightly

matrix

III. Physiological Features of Bone TissueA. Main Functions of the Bones & Skeletal System:

(Quick Glance) 1. ___________________or _______________ -

occurs in ___________________ only. 2. __________ - provides a framework for muscles to

attach to. 3. __________________ (detailed later) 4. _____________________ - works with muscles 5. __________ heart & other internal organs 6. _____________________________ in yellow

bone marrow. Acronym help: BS MA PhD

Support

ProtectsAssists In Movement

Mineral Homeostasis

Blood Cell Production

Deposits & stores adipose tissue

hemopoiesisRed bone marrow

B. Bone formation & ossification1. Definition of ossification:

_____________

_________________________________

2. When does ossification occur?a. begins about the ________ week

of embryonic life and continues into ___________ (ages18-25).

the process of bone formation

6th

adulthood

3. Two methods of ossification:a. _________________________- bone forms directly on or in loose fibrous

connective tissue.i. Where does this occur?

1. _____________________2. _____________________

Intramembraneous

Flat bones of skullMandible (lower jaw)

b. ____________________- bone forms within the cartilage. ____________________ in the body form this way.

EndochondralMOST BONES

4. Process of endochondral ossification:STEP #1:________________________________Development of the Cartilage Model

a). fetal _______________ cells crowd together in the shape of a future bone. (mesenchymal cells are embryonic tissue cells from which ALL connective tissue arises.)

mesenchymal

b). mesenchymal cells turn into _________________.chondroblasts

c). chondroblasts produce _________________ cartilage and the _________________ - membrane around the cartilage.

hyaline

perichondrium

STEP #2. _________________________________Growth of Cartilage Model

a). Chondroblasts become ________________ and some start to burst, triggering _________________.b). Remaining chondrocytes die b/c they cannot get enough _____________ in the calcifying matrix.c). When they die, _____________ form and merge into small cavities.

chondrocytescalcification

nutrients

lacunae

STEP #3. _________________________________Development of Primary Ossification Center

a). Primary ossification proceeds ____________________________.inward

b). A nutrient _________________ penetrates the middle of the cartilage.c) This stimulates _______________ cells to become ___________________ which lay the matrix to form the __________________ of spongy bone

artery

Osteogenic osteoblasts

trabeculae

d). ____________________ dissolves some of the newly formed trabeculae to create the ____________________ which fills with _____________________________.

Osteoclasts

Medullary cavity

Red bone marrow

STEP #4. _________________________________Development of Secondary Ossification Center

a). Like primary ossification except the bone remains as _______________.Spongy bone

STEP #5. _________________________________Formation of articular cartilage and epiphyseal plate

a). ________________ cartilage is replaced with ___________________ cartilage.

hyaline

articular

b). ______________ remains.

Spongy bone

c). ____________________ is the only remaining hyaline cartilage that allows the bone to ______________ until it calcifies. (usually between 18-25).

Epiphyseal plate

lengthens

IV. Homeostasis in Bone Tissue & Complications from an Imbalance

A. _____________________- the study of bone structure and the treatment of disorders.

Osteology

B. Bone Tissue “regeneration”:

1. old bone is constantly being ___________ by osteoclasts & new

bone tissue is being formed by _______________.(EVEN IN ADULTHOOD.)

resorbed

osteoblasts

C. Normal Bone Metabolism depends on:1. Adequate dietary amounts of:

a. minerals- ____________________ _____________________________

b. vitamin - _____________________

2. Hormone interaction – There are ______ hormones that play a role in bone homeostasis.

(Bone resorption hormones – PTH, cortisol; Bone formation – calcitriol, calcitonin, estrogen, thyroid,

insulin, growth hormone, insulin growth factors)

calcium, phosphorus & magnesium

C, A, D

9

D. How bone aids in the homeostasis of Calcium in the blood:

1. if blood-calcium levels are too __________, PTH

(___________________), from the parathyroid gland is released which activates the osteoclasts to _______________ calcium into the blood via resoprtion.

low Parathyroid hormone

release

2. If blood-calcium levels are too _________, then the thyroid gland releases _________________________ which activates the osteoblasts to take up calcium via bone formation.

3. Effects of calcium imbalance:a. Too low ______________________b. Too high ______________________

high

calcitonin

Breathing stopsHeart stops

Calcium Homeostasis Song (Tune: Jingle Bells, start with “Dashing…..”)

• If calcium gets low • Parathyroid goes to work• Releases PTH • Bones give up calcium• Kidneys take in less• So it stays in the blood• Vitamin D makes intestines take it from

grub.

Song continued…• If calcium gets too high • Stimulates thyroid• Thyroid makes calcitonin• To bring the level down• Calcitonin stimulates deposition in the

bones• Kidney leave more calcium in urine • Now we’re done!

E. Impact on Human Growth Hormone (hGH) on Bone Homeostasis

1. hGH stimulates ___________________ to make more _________________ which will cause bone formation.

chondrocytescartilage

2. effects of hGH imbalance:a. Undersecretion:

i. ______________________ - when too little hGH is secreted and the

epiphyseal plate closes too soon.

Pituitary dwarfism

b. Oversecretion:i. during ________________ could lead

to ___________________ which is caused by an abnormal lengthening of bones.

childhoodgigantism

• Gigantism slide here

ii. During _________________ could lead to ___________________ which causes a thickening of the hand, feet, cheek and jaw bones. (bones won’t lengthen b/c epiphyseal plate is already calcified).

adulthoodacromegaly

• Pic of NFL issue and growth hormone here

F. Maintaining Bone Mass1. How can bone mass be maintained or strengthened?

a. ________________________i. Why?

1. mechanical stress (like the pull of gravity or the pull

of skeletal muscles) ____________________ bones.

Weight bearing Exercise

Strengthens and thickens

2. How can bone mass be lost?a. when bone ________________ occurs faster than bone formation. In healthy individuals, this happens when:

i. ___________________________ii. _______________ - break in bone

resorption

A limb is unusedA bone fractures

1. four descriptions of fractures:a. _____________________ - an incomplete break across the bone,

such as a crack.

Partial fracture

b. _______________________- a complete break across the bone so that the bone is in two or more pieces.

Complete Fracture

c. _______________________ - the fractured bone does not break through the skin. (It could be ________________ or ________________)

Closed fracture

partial complete

d. ________________________- the broken end of the bone protrudes through the skin. (Can only be a ________________ fracture.)

open fracture

compound

G. ____________________- a condition of porous bones caused by a depletion of ____________ in the body.

1. What can it cause?a. ______________________b. _________________(especially

hip fractures)c. ______________________d. ______________________

Osteoporosis

calcium

Bone mass lossfractures

Shortened height (hunch back)Bone pain

2. Who is most likely to get it & why?a. ____________________- estrogen (an osteoblast stimulator) declines dramatically during menopause.

3. What can be done to prevent getting it later in life?

a. ________________________b. ________________________

Middle aged women

Adequate calcium in dietWeight bearing exercise in early years