AP 1 Lecture Exam 3

general functions of bones

support and protection

levers for movement

hematopoiesis

storage of mineral and energy reserves

hematopiesis definition

blood cell production, occurs in red bone marrow CT

what minerals are stored in the bone

calcium and phosphate

gross anatomy of bones

highly vascularized (spongy bone regions)

nutrient foramen

high sensory component

what is the nutrient foramen

small opening or hole in bone, artery entrance and exit

what is red bone marrow (myeloid)

soft connective tissue

hematpoietic

hematopoiesis definition

biological process by which body produces all of its blood cells

driven by hematopoietic stem cells, takes place primarily in the bone marrow

what is yellow bone marrow

product of red bone marrow degeneration as child matures

fatty substance

can convert back due to severe anemia

facilitates production of additional erythrocytes

what is bone connective tissue (osseous connective tissue) composed of

primary component of bone

composed of cells and extracellular matrix

4 types of cells in bone connective tissue

osteoprogenitor cells

osteoblasts

osteocytes

osteoclasts

what are osteoprogenitor cells

bone stem cells from mesenchyme

during cell division committed cell is produced that matures to become osteoblast

*stem cells are located in periosteum and endosteum

what are osteoblasts

immature bone cells

synthesize and secrete osteoids

*later undergo calcification

*produce new bone

what are osteocytes (hollow cells)

mature bone cells derived from osteoblasts (lost bone-forming ability)

become embedded within calcified osteoid (organelles are still functioning)

*maintain bone matrix and detect mechanical stress on a bone

what are osteoclasts (broken)

multinuclear cells

*derived from fused bone marrow cells

phagocytic cells involved in breaking down bone in bone resorption

composition of extracellular (bone) matrix

organic components

inorganic components

what are the organic components

osteoids

*gives tensile strength (resists stretching)

*bone flexibility

what are the inorganic components

salt crystals: calcium phosphate Ca₃(PO₄)₂

*interacts with calcium hyroxide (forms crystals: hydroxyapatite Ca₁₀(PO₄)₆(OH)₂

*harden matrix and give rigidity of the bones

bone formation (ossification/osteogenesis) definition

formation and development of bone connective tissue

when does ossification begin (age), when does it end (age)

in embryo, continues after brith and as the skeleton grows during childhood and adolescence

ends 20-25 years old

*by 8th-12th weeks of embryonic development skeleton beings forming from either thickened condesations of mesenchyme or hyaline cartilage model of bone

what does bone formation begin with, what happens

starts with hyaline cartilage

then osteoblasts secrete osteoid

calcification (mineralization occurs) → deposition of hydroxyapatite crystals

what does bone matrix formation require

vitamin D: enhances calcium absorption from GI tract

vitamin C: collagen formation

calcium and phosphate for calcification

what happens in bone resorption

1. bone matrix is destroyed by substances released from osteoclasts

2. lysosomes realease:

• proteolytic enzymes → digest organic matrix components

• hydrochloric acid (HCl) → dissolves inorganic mineral parts of matrix

3. osetolysis

4. calcium and phosphate ions enter extracellular fluid of nearby tissues then blood

what is osteolysis

release of stored calcium and phosphate from bone matrix

when does bone resorption occur

occurs during bone remodeling

blood calcium levels are low

main funcitonal unit of bone

osteons

osteoids

collagen proteins, semisolid ground substance of proteoglycans and glycoproteins, semisolid, later calcifies

what happens in intramembranous ossification

1. ossification centers from within thickened regions of mesenchyme (8-12 weeks)

2. osteoid undergoes calcification (traps osteocytes)

3. woven bone and surrounding periosteum form

4. lamellar bone replaces woven bone, as compact and spongy bone form

what is intramembranous ossification (dermal ossification)

bone growth within a membrane

what is enchondral ossification

within cartilage

*begins with hayline cartilage model

*produces most bones of skeleton (upper and lower limbs, pelivs, vertebrae, ends of clavicle)

what happens in enchondral ossification

1. fetal hyaline cartilage model develops (8-12 weeks)

2. cartilage calcifies, and a periosteal bone collar forms around diaphysis (fetal period)

3. primary ossification center forms in the diaphysis (fetal period)

4. secondary ossification centers form in the epiphysis (newborn to child)

5. bone replaces almost all cartilage except the articular cartilage and epiphyseal plates

6. lengthwise growth continues until the epiphyseal plates ossify and form epiphyseal lines

when does the epiphyseal plate convert to epiphyseal line

between 10-25 years old

compact bone (cortical bone) characteristics

relatively rigid, dense

80% of bone mass

spongy bone (cancellous or trabecular bone) characteristics

appears porous (full of trabeculae)

internal to compact bone

20% of bone mass

has importance with weight

bone remodeling definition

constant dynamic process of continual addition of new bone tissue and removal of old bone tissue

what is bone remodeling based on

blood calcium levels

activities of osteoblasts, osteocytes, and osteoclasts

hormones and mechanical stress

hormones that promote bone growth

growth hormone, thyroid hormone, calcitonin, sex hormones

hormoes that inhibit bone growth (or increase bone resorption)

parathyroid hormone, calcitriol, glucocoricoids, serotonin

what does growth hormone (somatotropin) do

*produced by anterior pituitary gland

stimulates liver to produce hormone called insulin-like growth factor (IGF)

stimulate growth of cartilage in epiphyseal plate (bone elongation)

what does thyroid hormone do

*secreted by thyroid gland

stimulates bone growth by stimulating metabolic rate of osteoblasts

continues after epiphyseal plate and line

*regulates normal activity at epiphyseal plates

what do sex hormones (estrogen and testosterone) do

stimulate osteoblasts

promotes epiphyseal plate growth and closure

what do glucocorticoids do (blood → sugar levels)

*released form adrenal cortex

regulate blood glucose level

increase bone loss

*in children impair bone growth in response to chronically high levels of glucocorticoids

what does serotonin do

neurotransmitter and hormone

role in rate and regulation of normal bone remodeling

*inhibits osteoprogenitor cells from differentiating into osteoblasts when there is chronically high levels of serotonin

what are the 2 primary hormones that regulate blood calcium

calcitriol

parathyroid hormone

what does calcitonin do

in childhood promotes calcium deposition in bone and inhibits osteoclast activity

response to high blood calcium levels

*minimal effects in adulthood

what does calcitrol do

increases blood calcium levels by encouraging bone resorption by osteoclasts and stimulating absorption of calcium ions

*from small intestine into the blood

negative feedback loop of blood calcium levels

1. stimulus: decrease in blood calcium

2. receptors: parathyroid gland detects decrease

3. control center: parathyroid gland, releases parathyroid hormone

4. PTH and calcitriol interact with major organs

   1. in bone: PTH and calcitriol act together to increase release of calcium from bone into the blood by increasing osteoclast activity → blood calcium levels increase

   2. in kidneys: stimulate kidneys to excrete less calcium in urine with decrease in calcium loss in urine → maintain blood calcium levels

   3. in small intestine: (unique to calcitriol) increase absorption of calcium from small intestine into blood → blood calcium levels increase if calcium is ingested as part of the diet and is available for absorption

5. net effect: elevating blood calcium → returning to preexisting levels

6. increase of blood calcium back to typical range inhibits further release of PTH

what happens in response to low blood calcium levels

PTH and calcitriol is released → increase blood calcium levels to preexisiting levels

what happens in response to high blood calcium levels

calcitonin is released (or stress from exercise) → decrease in blood calcium levels

rickets

disease caused by vitamin D deficiency in childhood

characterized by deficient calcification of osteoid tissue (bowlegged)

disturbances in growth

hypocalcemia (low blood calcium)

tetany (cramps and muscle twitches)

calcitonin talks to what bone cell

osteoblast

PTH and calcitriol talks to what bone cell

osteoclast

what is a fracture

breaks in bone

what are the types of fractures

stress fracture

pathologic fracture

simple fracture

compound fracture

stress fracture definition

thin break caused by increased physical activity

pathologic fracture definition

occurs in bone weakned by disease

simple fracture (closed)

broken bone not penetrating skin

compound fracture (open)

one or both ends of the bone pierce overlying skin

process of bone repair after fracture

1. fracture hematoma forms

2. fibrocartilaginous (soft) callus forms

3. hard (bony) callus forms

4. bone is remodeled

what are the structural classes of the joints

fibrous

cartilaginous

synovial

what is a fibrous joint

bones held together by dense conenctive tissue

no joint cavity

*immobile or slightly mobile

what is a cartilaginous joint

bones joined by cartilage (hyaline or fibrocartilage)

no joint cavity

*immobile or slightly mobile

what is a synovial joint (most complex)

bones joined by ligaments with fluid-filled joint cavity seperating bone surfaces

*most joints in the body

diarthroses (freely mobile)

what are the funcitonal calsses of joints (degree of movement)

synarthrosis

amphiarthroses

diarthroses

what is synarthrosis

immobile joints

can be fibrous or cartilaginous joints

what is amphiarthroses

slight mobile joints

can be fibrous or cartilaginous joints

what are diarthroses/synovial joints

freely mobile joints

all synovial joints

3 most common types of fibrous joints

gomphoses (synarthrosis)

sutures (synarthrosis)

syndesmoses (amphiarthroses)

what are synchondroses joints

bone joined by hyaline cartilage

immobile (synarthrosis)

what are symphyses joints

fibrocartilage between articulating bones

slight mobility (amphiarthroses)

basic features of synovial

articular capsule and joint cavity

synovial fluid

articular cartilage

ligaments, nerves, and blood vessels

classes by movement of synovial joints

uniaxial joint

biaxial joint

multiaxial

uniaxial joint

1 plane/axis

biaxial joint

2 planes/axes

multiaxial joint

multiple planes

classes of synovial joint surfaces (least → freely mobile)

1. uniaxial

   1. plane joints

   2. hinge joints

   3. pivot joints

2. biaxial

   1. condylar (lypsoid) joints

   2. saddle joints

3. multiaxial

   1. ball-and-socket joints

first class levers

fulcrum between effort and resistance

second class levers

resistance between fulcrum and effort

third class levers

effort applied between resistance and fulcrum

temporomandibular joint

articulation between head of mandible and temporal bone

sternoclavicular

only joint where axial meets appendicular

*stabalize movements of entire shoulder

acromioclavicular joint

works with glenohumeral joint to give the upper limb full range of movement

knee joints

largest and most complex diathrosis (synovial)

primarily a hinge joint

tibiofemoral joint

patellofemoral joint

where is tibiofemoral joint

between condyles of femur and condyles of tibia

where is patellofemoral joint

between patella and patellar surface of femur

hierarchy of skeletal muscle

entire muscle → connective tissue epimysium

bundles of fasicles → epimysium

bundles of muscle fibers → perimysium

muscle cells → sarcolemma

myofibrils → sarcoplasm and sarcoplasmic reticulum

bundles of myofilaments → sarcoplasmic reticulum

protien filaments → sarcoplasm

what kind of channles are in the sarcolemma and t-tubules

voltage-gated Na⁺ channel

voltage-gated K⁺ channel

voltage sensitve Ca²⁺ channel

what are the regulatory proteins of the thin filament

tropomyosin

troponin

myoglobin of skeletal muscle

within cells allows for storage of oxygen used for aerobic ATP production (aerobic respiration → long term)

stored energy of skeletal muscle

glycogen

creatine phosphate

glycogen is used for what

when fuel is needed quickly (glycolysis → short term)

creatine phosphate is used for what

quickly give up its phosphate group to replenish ATP supply (immediate)

main functional unit of skeletal muscle

sarcomere

overview of events in skeletal muscle contraction

1. neurotransmitter junction: excitation of skeletal muscle fiber

2. sarcolemma, t-tubules, and sarcoplasmic reticulum: excitation-contraction coupling

3. sarcomere: crossbridge cycling

what do muscle fibers exhibit

RMP

*RMP of muscle cell is -90mV

RMP established by leak channels and Na⁺/K⁺ pumps (3 out/2 in)

what is sarcolemma

plasma membrane of a skeletal muscle fiber

what are t-tublues

deep invaginations of the sarcolemma

network of membranous tubules to the sarcoplasmic reticulum

where are the (2) voltage-gated channels (Na⁺and K⁺)

within membrane of sarcolemme (along its length)

t-tubules

thick filaments anatomy and physiology

assembled bundles of myosin protein molecules, each myosin has 2 strands: globular head and elongated tail

head contains binding site for actin of thin filaments and catalytic ATPase where ATP splits into ADP + P

2 tails of myosin intertwined

thin filaments anatomy and physiology

composed of 2 strands of actin protein twisted around each other

g-actin spherical molecules → myosin binding site

f-actin fibrous strand

tropomyosin anatomy and physiology

twisted filament protein

cover small regions of actin strands → myosin bidning sites