anatomy honors - ch. 6-7: skeletal tissue & system

functions of bones

- support body & organs
- protect brain, spine & vital organs
- movement w/possible assistance (tendons, muscles, joints)
- growth
- blood cell formation (hematopoiesis occurs in marrow)
- triglyceride (fat) storage (source of energy)

2 bone groups

1. axial (80 bones):
- skull (28)
- vertebrae (26)
- rib cage (26)

2. appendicular (126 bones)
- shoulders/arms (32x2)
- hips/legs (31x2)

diaphysis

- shaft filled w/marrow
- only found in long bones

epiphysis caps

- hyaline cartilage plate
- metaphysis at each end of a long bone

periosteum

- white outer covering
- vascular
- attached by sharpey's fibers
- compact bone

endosteum

- covers inner part of bone (trabeculae)

yellow marrow found in:

- only in adults
- in diaphysis and most of epiphysis (femur/humerus)

red marrow found in:

- infants: all bones
- adults: all bones (irregular, short, flat, epiphysis)
- those who are anemic: it reverts from yellow

2 bone textures

1. compact:
- dense/smooth external layer

2. spongy (aka cancellous):
- marrow that fills spaces in a honeycomb structure (trabeculae)
- prevents fractures/stress all on one bone
- contains hematopoietic tissue

anatomy of compact bone (superficial to deep)

1. Vessels/Nerves
2. Central (Haversian) Canal
3. Lamella
4. Canaliculus
5. Lacuna
6. Osteocyte

7. Osteon (Haversian system)

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8. Perforating (Volkmann's) Canal
9. Circumferential Lamellae
10. Sharpey's Fibers
11. Periosteal Vessels/Nerves
12. Periosteum

physiology of compact bone

- contain nutrients and waste
- maintain bone matrix (solution)
- receptors for bone deformation

4 major cell types in osseous tissues

1. osteogenic cells = mitotic cells found in periosteum & endosteum

2. osteocyte = cells filled w/lacunae (pores) connecting many osteons with canaliculi (canals); distribute nutrients & waste

3. osteoblast = bone-forming cell (osteoid)

4. osteoclast = bone-destroying cell

3 types of skeletal cartilage

1. hyaline (most abundant)
2. elastic
3. fibrocartilage

4 hyaline cartilages & functions

1. articular hyaline cartilage = found at ends of long bones at movable joints
2. costal hyaline cartilage = connects ribs to sternum
3. respiratory hyaline cartilage = makes up larynx (voice box), reinforces air passages
4. nasal hyaline cartilage = supports external nose

elastic cartilage

found in ear & epiglottis (flap of cartilage that covers windpipe while swallowing)

fibrocartilage

- highly compressible
- found in knees & discs between vertebrae
- strongest cartilage tissue due to location (needs to support most weight)

# of birth bones vs. # of adult bones

300 vs. 206

5 bone types

1. long bones
2. short bones
3. flat bones
4. sesamoid bones
5. irregular bones

function of long bones

- make up the appendicular skeleton
- support weight
- facilitate movement

function of short bones

- provide stability
- provide some movement
- found in appendicular (carpal/tarsal)

function of flat bones

- protect internal organs (brain, hearts, lungs)
- found in axial skeleton

function of sesamoid bones

- embedded in tendons
- found in appendicular (pedal, manus, patellar)
- protects tendons from wear & tear
- made of regular dense connective tissue
- very resilient

function of irregular bones

- protect axial & appendicular skeleton (skull, sacrum, spine, vertebrae, pelvic girdle)

2 types of bone markings

1. projections (bulges)
- grow outwards from bone surfaces
- called: facet/process

2. depressions (openings)
- indentions/pathways for vessels
- called: fossae/sinuses/foramina

3 parts in the anatomy of a long bone

1. diaphysis
2. epiphysis caps
3. epiphyseal plates

epiphyseal plates

- plates in children
- replaced by epiphyseal lines in adults

why aren't ribs considered long bones?

they don't have epiphysis

2 types of bone coverings

1. periosteum
2. endosteum

2 types of marrow

1. red
2. yellow

chemical composition of bone

35% organic: osteocytes, osteoclasts, osteoblasts
- give flexibility & tensile strength

65% inorganic: hydroxyapatites (mineral salts), calcium phosphates
- allow bone to exist after death

bone development

ossification/osteogenesis: bone formation
2 stages:
1. embryos: formation of bony skeleton
2. post-natal: bone growth

bones collapse/rebuild to maintain homeostasis; bone becomes stronger after being filled w/calcium

bone repair (stages)

1. day 1 - blood vessels in bone tear & hemorrhage (hematoma) to form a blood clot
2. day 3 - fibroblasts & osteoblasts reconstruct bone
3. day 9 - new trabeculae form (completes in 2 months)
4. bone remodeling occurs for 2 months

bone remodeling

remodeling = deposit & resorption

deposit: calcium & phosphate added where the bone is injured/strength is needed

resorption: osteoclasts break down bone matrix

how is bone remodeling controlled & why does it occur?

- hormonal & mechanical stress
- scheduled time for bones to go through cell cycle

hormonal control

- PTH (parathyroid hormone) ↑ calcium when levels in blood drop
- osteoclasts resorb bone (↑ calcium in blood)

how hormones regulate bone growth

WHO is boss?: PITUITARY GLANDS (brain) release growth hormone
HOW much?: THYROID (neck) hormones
WHEN?: SEX (sperm/egg) hormones
WHERE?: EPIPHYSEAL PLATES

mechanical stress

wolff's law = bone grows in response to demands placed on it;
STRESS bends bone, having a thick midway point

postnatal bone growth

- long bones grow in infancy & youth
- most bones stop growing during adolescence
- nose and lower jaw grow throughout life

6 common fractures

1. comminuted: >3 bone pieces shattered
2. compression: crushed from a fall
3. spiral: excessive twisting in a sport injury
4. epiphyseal: epiphysis breaks from diaphysis (bad for kids)
5. depressed: bone smashes inward
6. greenstick: incomplete break (hairline)

osteoporosis

= bone resorption not balanced w/bone deposit, resulting in porous/light bones

- common injuries: compression fractures in spine & broken hips

people at risk:
- postmenopausal women (estrogen maintains healthy bone density)
- petite bodied people
- inactive/immobile people (atrophy)
- diet lacking in calcium/protein
- low PTH

treatment: calcium & vitamin D supplements, weight training, prescriptions, drinking fluoridated water, avoiding carbonated drinks

paget's disease

- pagetic bone (excessive bone deposit & resorption, forming high ratio of spongy to compact bone) fills marrow & has areas of unequal thickness
- osteoclasts minimize, osteoblasts continue to work

other bone diseases

1. rickets: caused by lack of vitamin D/calcium; affects children; causes bowed legs, deformed pelvis, wide epiphyses

2. osteoarthritis: caused by inflamed/damaged joints; affects elderly, mostly women; causes 'wear & tear' articular cartilage to break down

3. rheumatoid arthritis: autoimmune disease; affects ages 30-50; causes stiff/tender joints

4. gouty arthritis: caused by buildup of uric acid that forms crystals in joints; inherited & affects mostly men; causes epiphyses to fuse & immobilize joints

skull

= 22 cranial & facial flat bones interlocked by sutures

- FORAMEN MAGNUM = opening where brain connects to spine
- SINUSES = air filled pockets to enhance voice & lighten skull
- HYOID BONE = only free floating bone attached by ligaments to temporal bone to utilize tongue

vertebral column

= 26 irregular bones

5 MAJOR REGIONS:
1. C1-7 (cervical)
2. T1-12 (thoracic)
3. L1-5 (lumbar)
4. sacrum: 5 fused
5. coccyx: 4 fused (tailbone)

ligaments = prevent spine from hyperflex/tension

cervical vertebrae

- C1 (Atlas) & C2 (Axis) both support head
- NO FIBROCARTILAGE in between
- does not have processes like other vertebrae

thoracic cage (aka bony thorax)

= consists of sternum, ribs, costal cartilage

sternum(breastbone) = 6 in. long, in 3 fused bones:
1. MANUBRIUM: articulates w/clavicle & rib 1-2
2. BODY: articulates w/costal cartilage of ribs 3-7
3. XIPHOID PROCESS: forms inferior end, ossifies until age 40; attaches to major muscles

ribs = 12 pairs attached posteriorly to thoracic vertebrae & curve toward anterior body surface
- point of attachment!
- 1-7: TRUE RIBS (attach to sternum via costal cartilage)
- 8-10: FALSE RIBS (rib 8 attaches to rib 7)
- 11-12: FLOATING RIBS don't attach anteriorly

2 parts of pectoral girdle

1. CLAVICLE: articulates to manubrium & braces scapulae to move arms laterally
2. SCAPULA: anchors biceps, helps lower/lift arm

upper limb

- arm: shoulder to elbow supported by HUMERUS
- forearm: humerus articulates RADIUS & ULNA (elbow)
- hand: CARPAL (short bones) & METACARPAL (long bones)
- PHALANGES (thumb & fingers): 14 bones

pelvic girdle

- attaches lower limbs to axial skeleton using ligaments
- thighs get closer to knees for balance
- pair of COXAL bones made of 3 bones, fused as adults:
1. ILIUM
2. PUBIC
3. ISHIUM

lower limb

- thigh: between hip & knee supported by FEMUR
- PATELLA: triangular bone articulates w/femur
- leg: between knee and ankle made by TIBIA (weight bearing) & FIBULA
- foot (PEDAL): includes arch & combo of foot bones, ligaments, tendons to distribute half of our standing/walking weight evenly to foot