Anatomy exam 2

Osteology

the study of bones

What are bones made of?

osseous tissue, blood, bone marrow, cartilage, adipose, nervous tissue, fibrous connective tissue

Ligaments

bone to bone

Tendons

muscle to bone

Five functions of the skeleton

1. Support

2. Protection

3. Movement

4. Electrolyte balance

5. Blood formation

Where is blood formed?

red bone marrow

What electrolytes are released from bone?

Ca +2, PO4 -2

Two types of osseous tissue

1. Compact bone

2. Spongy bone

Long bones

longer than wide (ex. femur)

Short bones

cube shaped bones (ex. carpals)

Flat bones

thin and flat (ex. cranium)

- compact bone on outsides and spongy in middle (bone sandwich)

Spongy bone

made of crossbars (trabeculae) with spaces filled of bone marrow

Irregular bones

Vertebrae, ear bones

Articular cartilage

- hyaline cartilage

- covers ends of long bones

Diaphysis

- shaft of long bones

- compact bone covering spongy bone

- only in long bones

Medullary cavity

- marrow cavity

- in shaft of long bones

Epiphysis

- ends of long bones

- mostly spongy bone

- only in long bones

Epiphyseal plate

- growth plate

- turns to epiphyseal line when fully formed

Periosteum

- 2 layer membrane

- Provides attachment to tendons and ligaments

- rich supply of nerve fibers and blood vessels

Nutrient foramina

minute holes in the bone surface that allows blood vessels to penetrate

Layers of periosteum

1. Fibrous layer

2. Osteogenic layer

Fibrous layer of periosteum

- dense irreg. CT

- outer layer

Osteogenic layer of periosteum

- osteogenic cells

- turns into bone

Endosteum

lines the medullary cavity

Sesamoid bones

short bones within tendons (ex. patella)

Osteon

- Haversian system

- fundamental unit

Lamella

bone matrix around an osteon

Concentric lamella

around the osteon

Circumferential lamella

a bony lamella that encircles the outer or inner surface of a bone

Lacuna

space containing the osteocyte

Central canal

- Haversian canal

- runs through each osteon

- nerves and blood vessels

Perforating canals

- Volkmann's canal

- perpendicular to central canal to link together

Canaliculi

microscopic canals between the lacunae of ossified bone

Red bone marrow

- myeloid tissue/hemopoietic tissue

- found in skull, vertebrae, ribs, sternum, and proximal heads of humerus/femur (in adults)

Yellow bone marrow

- fat storage

- can convert to red marrow in extreme cases of anemia

Four major types of bone cells

1. osteogenic cells

2. osteoblasts

3. osteocytes

4. osteoclasts

Osteogenic cells

- bone stem cells

- found in periosteum and endosteum

- multiply continually

Osteoblasts

- bone forming cells

- secrete osteoid to form bony matrix

- nonmitotic

Osteocytes

- mature bone cells found in lacunae

- maintain bony matrix

- stress sensors and influence bone remodeling

Osteoclasts

- bone dissolving cells (osteolysis)

- NOT from osteogenic cells, from stem cells

Osteoid

unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen

Inorganic materials in bone

1. 85% Hydroxyapatite (crystalized calcium phosphate salt)

2. 10% calcium carbonate

3. 5% Magnesium, sodium, potassium, fluoride, sulfates, carbonates, and hydroxide ions

Ossification (osteogenesis)

formation of bone

3 major processes of ossification

1. Bone formation (embryos - early childhood)

2. Bone growth (embryos - early 20's)

3. Bone remodeling (lifelong)

Endochondral ossification

replacing hyaline cartilage with bone

Intramembranous ossification

bone develops from fibrous membrane

Appositional growth

- widen

- same as intramembranous ossification

Bone remodeling

- deposition and resorption

- bone mass stays the same (if healthy)

Wolff's law

Bone remodel in response to stress on the bone

Ectopic ossification

abnormal calcification of tissues (bone where should be no bone)

Arteriosclerosis

calcification of the arteries

Normal calcium levels

9.2-10.4 mg/dL

Hypocalcemia

- deficient calcium in the blood

- causes excitable muscles and neurons

- can cause rickets

Tetany

- constant muscle contraction

- caused when calcium blood levels reach below 6mg/dL

Trosseau's sign

hand spasm when bp cuff inflated

Hypercalcemia

- excessive calcium in the blood

- slow reflexes, depression of NS, cardiac arrest

Hormones that regulate calcium homeostasis

1. Calcirol

2. Calcitonin

3. Parathyroid hormone

Formation of calcitriol

1. UV causes keratinocytes to turn cholesterol to vit. D

2. Liver converts vit. D to calcidiol

3. Kidneys converts calcidiol to calcitriol

Calcitonin

- lowers blood calcium levels

- secreted by thyroid gland

Parathyroid hormone

- raises blood calcium levels

- increases osteoclast production to free calcium ions and send to blood stream

- increases kidney's ability to absorb calcium

Cortisol

- inhibits osteoclast activity

- can cause osteoporosis if too much is secreted

Estrogen

- stimulates osteoblasts

- prevents osteoporosis

- after menopause, it's created less causing higher chances of osteoporosis

Growth hormone

stimulates epiphyseal plate activity

Insulin

stimulates bone growth

Testosterone

stimulates osteoblasts

Thyroid hormone

- modulates activity of growth hormone, ensuring proper proportions

- in excess can cause hypercalcemia

Vit C

required for collagen synthesis

Fracture

broken bone

Stress fracture

purely mechanical damage

Pathological fracture

break in a bone weakened by some other disease

Displaced fracture

fractured ends are completely out of place

Nondisplaced fracture

bone ends retain their normal position

Complete fracture

bone is broken all the way through

Incomplete fracture

- greenstick

- Bone is still connected in someplace

Compound fracture

bone breaks through skin (open)

Simple fracture

bone does not break through the skin (closed)

Reduction of bone

Manipulating the bone back to proper position

Closed reduction

- external reduction

- bones are in a cast

- no surgery

Open reduction

- internal fixation

- bones are secured with surgical pins and wires

Stages of bone healing

1. hematoma formation

2. fibrocartilage callus formation

3. bony callus formation

4. bone remodeling

Osteomalacia/rickets

bones become softer because of a vitamin D deficiency (can't become mineralized)

Osteoporosis

- bone resorption is much greater than deposition

- hollow and weakened bones

Step 1 of endochondral ossification

- mesenchyme develops into hyaline cartilage covered with perichondrium

- chondrocytes produce cartilage to increase thickness

Step 2 of endochondral ossification

- primary ossification center forms

- perichondrium starts to produce osteoblasts

- osteoblasts secrete bony layer around diaphysis

Step 3 of endochondral ossification

- blood vessels infiltrate the center of diaphysis

- osteoblasts deposit bone at the primary ossification center

- secondary ossification center is formed

Step 4 of endochondral ossification

- osteoclasts break down newly formed spongy bone and create the medullary cavity

Step 5 of endochondral ossification

- cartilage is only articular or in growth plate

- epiphysis fill with spongy bone

Number of bones in axial skeleton

80

Axial skeleton

Portion of the skeletal system that consists of the skull, rib cage, and vertebral column

Appendicular skeleton

Bones of the limbs and limb girdles that are attached to the axial skeleton

Functions of axial skeleton

-supports and protects organs in body cavities

-attaches to muscles of: head, neck, trunk, respiration, and appendicular skeleton

Cranial bones

- 8

- protect brain and attachment for facial muscles

Facial bones

- 14

- secure teeth

- contain cavities for sense organs

Sinuses

- cavities in the skull that surround the nasal area

- warm and humidify air

- reduces weight of skull

- enhances resonance of the voice

Fontanelles

soft spots normally present on the skull of a newborn

Anterior fontanelle

- takes 2 years to fully ossify

- large soft spot on infant's head

Malleus

- hammer

- first of the three auditory ossicles of the middle ear

Incus

- anvil

- middle of the three auditory ossicles of the middle ear

Stapes

- stirrup

- last of the three auditory ossicles of the middle ear

intervertebral discs

fibrocartilage pads that separate and cushion the vertebrae