BIO 212... Flashcards
Growth Hormone
stimulates liver to produce somatomedin, which causes cartilage proliferation at epiphyseal plate and resulting bone elongation
Thyroid Horomone
stimulates bone growth by stimulating metabolic rate of osteoblasts
Calcitonin released by the thyroid hormone
promotes calcium deposition in bone (stimulates osteoblasts), and inhibits osteoclast activity
stimulates osteoblasts in response to increased blood calcium levels
Decrease calcium uptake from intestines and reabsorption from urine.
Parathyroid Hormone (PTH)
Works with calcitriol (vitamin D). Stimulates osteoclasts in response to decreased blood calcium levels (bone resorption). Increase calcium uptake in intestines (vitamin D), and increases calcium reabsorption from urine.
What causes bone formation rate greater than cartilage growth, initiates the closing of the growth plate.
Stimulates osteoblasts.
Stimulates both cartilage growth and bone formation, but calcification is stimulated more causing the epiphyseal plate to close –> forms epiphyseal line.
Estrogen and testosterone
Glucocorticoids
increase bone loss and, in children, impair growth when levels are high
Serotonin
inhibits osteoprogenitor cells from differentiating into osteoblasts at high levels
- Ossification centers form within thickened regions of the mesenchyme beginning at the 8th week of development.
- Thickened cells in the mesenchyme divide, and the committed cells that are formed then differentiate into osteoprogenitor cells. Some of these become osteoblasts and begin to secrete osteoid.
- Osteoid undergoes calcification. Entrapped osteoblasts become osteocytes.
- Woven bone (immature) forms and then mesenchyme that surrounds woven bone begins to thicken and eventually organizes to form the periosteum.
- Lamellar bone replaces woven bone as compact bone and spongy bone form
Intramembranous Ossification
bone growth within membrane – mesenchyme
Woven bone becomes_______?
Lamellar bone
Intramembranous ossification produces what type of bones?
Flat bones
Produces long bones
Endochondral ossification
bones form within cartilage
1) Fetal hyaline cartilage model develops
2) Cartilage calcifies and a periosteal bone collar forms. As the cartilage calcifies, blood vessels grow toward the cartilage and start to penetrate the perichondrium around the shaft.
3) The primary ossification center forms in the diaphysis.
4) Secondary ossification centers form in the epiphysis
5) bone replaces almost all cartilage except the articular cartilage and epiphyseal cartilage
6) lengthwise growth continues until the epiphyseal plates ossify and form epiphyseal lines
Endochondral ossification - produces most of the bones in the skeleton
Zone 1
Zone of resting cartilage
- nearest the epiphysis. Resembles mature and healthy hyaline cartilage. Secures the epiphysis to the epiphyseal plate.
Zone 2 – bone growth in length mostly occurs here
Zone of proliferating cartilage
-chondrocytes undergo rapid mitotic division, enlarge slightly, and become aligned into longitudinal columns of flattened lacunae. Parallel to diaphysis.
Zone 3
Zone of hypertrophic cartilage
-chondrocytes cease dividing and begin to hypertrophy (enlarge in size)
Zone 4
Zone of calcified cartilage
-minerals are deposited in the matrix between the columns of lacunae; destroys the chondrocytes
Zone 5
Zone of ossification (deposition)
-Walls break down between lacunae. Chondrocytes die. Spaces invaded by capillaries and osteoprogenitor cells from the medullary cavity. New matrix of bone is deposited on top of the remaining calcified cartilage matrix.
Where does bone remodeling occur?
Bone remodeling does not occur at the same rate everywhere in the skeleton
periosteum and endosteum
Bone remodeling is dependent upon…
the coordinated activities of osteoblasts, osteoclasts, and osteocytes. Activity of these cells are influenced by hormones and stress
Bone remodeling also occurs in response to…
mechanical stress occurs in the form of weight-bearing movement and exercise, and it is required for normal bone remodeling.
Osteoblasts increase synthesis of osteoid, and this is followed by deposition of mineral salts. Bone strength increases over a period of time in response to mechanical stress. Results from skeletal muscle contraction and gravitational forces.
Wolff’s Law
Bone grows in response to forces or demands placed on it
Mechanical stress is detected by____
osteocytes, and communicated to osteoblasts triggering an increased synthesis of osteoid adding bone strength
Femoral growth is used to determine______
Age
- epiphyseal plates fuse progressively at set ages
- these ages differ among males and females in specific regions with females typically closing at an earlier age
- Know that we can have multiple epiphyseal plates.
- They can become active and close at different times.
- And there are differences between genders.
Steps of Fracture and Bone Repair
1.
- A fracture hematoma forms from broken vessels and clotted blood (converted to granulation tissue)
Bone Fracture and Repair
2.
- A fibrocartilaginous (soft) callus forms - body’s splint to keep bones lined up. Regenerating blood vessels enter this area.
Bone Fracture and Repair
3.
- A hard bony callus forms
- osteoprogenitor cells adjacent to fibrocartilaginous callus become osteoblasts and produce trabeculae of primary bone. FC is replaced by this bone
- primary bone (woven bone) forms. It has spongy bone, but no compact bone.
Bone Fracture and Repair
4.
- The bone is remodeled
- when you take woven bone and you turn it into mature lamellar bone. Remodel using osteoblasts and osteoclasts in order to reform medullary cavity.
Reduction in bone mass significant enough to compromise normal function. A significant percentage of older women, and smaller proportion of men suffer from this.
Result of degradation of arches and trusses of trabecular bone.
OSTEOPOROSIS - decrease in density of bone. Weakens the bone, and more prone to fracture
The bones of the skeleton become weaker and thinner, resulting in insufficient ossification. All become slightly _________
Osteopenia
become osteopenic
Cranial bones interconnection by dense connective tissue forming “soft spots” - ease for travel through birth canal
Anterior fontanelle and posterior fontanelle
largest - posterior closes 9 months
smallest - anterior closes 15 months
-replaced by cranial sutures
Areas of the neuron that is influenced by action potentials in saltatory conduction
neurofibril node (large number of voltage gated Na+ channels and K+ voltage gated channels)
The type of conduction that occurs in myelinated regions
saltatory conduction
unmyelinated axons have this kind of conduction
continuous conduction
The type of summation that occurs when a single presynaptic neuron repeatedly releases neurotransmitter to produce multiple EPSP’s in the postsynaptic neuron at the same location repeatedly within a short period of time
temporal summation
Occurs when multiple presynaptic neurons release neurotransmitter at various locations onto the receptive segment, thus generating EPSPs and IPSPs, or both in the postsynaptic neuron.
spatial summation
The two types of summation.
Type of signals from temporal
Type of signals from spatial
temporal and spatial
temp - EPSPs
spatial - EPSPs and IPSPs
Type of common neurotransmitter that binds to nicotinic receptor or muscarinic receptor
acetylcholine neurotransmitter
acetylcholine neurotransmitter is synthesized how and where?
synthesized from acetate and choline and then stored within synaptic vesicles within the synaptic knob of the neuron. Released by exocytosis into the synaptic cleft in response to the arrival of an action potential in the presynaptic neuron
Skeleton Functions
Hemopoiesis (blood cell formation), support and protection, movement, storage of minerals and energy reserves
Bone building cells beneath the _________ lay down bone to form ridges around a blood vessel
periosteum
Once a tunnel of bone is formed around a blood vessel, the bone building cells of the __________ lay down bone in concentric circles that fill in the tunnel.
endosteum
Encourages calcium deposition from blood to bone
calcitonin - released by the thyroid
Sex differences in the skull…
male skulls are
heavier, larger, longer and thicker than female skulls
Male skulls tend to have larger ______ with a more massive _______ process and __________ bone
jaws, mastoid, zygomatic bone
Male foreheads tend to be more _______ while female foreheads are more _____
slopped, vertical
Sex differences in the pelvis
Female pelvis is ________ and _______
Larger and wider than males
Pelvis is used to determine ______ and ______
sex and age
Females have a rounder pelvic inlet for
childbirth
The angle between the inferior pubic rami is acute ______ in men, but obtuse _______ in women. Accordingly, the angle is called the ______ angle in men, and _____ in women.
70 degrees, 90-100 degrees, subpubic angle v, pubic arch
