Lecture Quiz 4 Flashcards
Briefly describe bone tissue’s replication - how much in how long?
very metabolically actibe
one gram of bony matrix may be gained or lost in any 24 hour period
bones are completely remodeled every three years
What causes bone remodeling and how long are cycles?
microfractures occur via everyday wear and tear and are healed by ongoing bone remodeling
occurs in 120 day cycles
Describe what osteoclasts do to bone
bone resorption
they release proteases which dissolve bone matrix and collagen
clear away damaged bone
they then release matrix-bound growth factors that chemically attract osteoblasts
Describe what osteoblasts do to bone
bone formation
occurs during last 100 days
fill in bony cavity with bone amtrix
release cytokines to attract osteoclasts
What is Wolff’s law in bone remodeling?
mechanical stress and grav ity provoke microfracturing and remodeling which leads to a formation of a stronger bone
What is the role of parathyroid hormone in bone remodeling?
PTH stimulate osteoclasts to reabsorb bone mineral
increases the production of an active form of vitamin A
comes from parathyroid glands
What is the role of calcitonin in bone remodeling?
slows down the activity of osteoclasts
released from thyroid gland
What is the role of sex hormones in bone remodeling?
testosterone and estrogen
stimulate osteoblasts and slow down osteoclasts
puberty - osteoblasts build more bone
How does menopause affect bone remodeling?
Dramatic decrease in estrogen leads to disturbance in balance of osteoblast and osteoclasts
this leads to low calcium and low vitamin d
can lead to osteoporosis
Can men be affected by osteoporosis?
Yes
decrease in testosterone happens with age
drop is not as dramatic as in women who reach menopause
What is the first stage of bone repair?
blood from ruptured blood vessels forms a hematoma, which provides a temporary splint
What is the second stage of bone repair?
a fibrous connective tissue connects the ends of a broken bone known as fibrocartilagenous callus
capillaries frow into hematoma
macrophages remove cell debris
fibroblasts, chondroblasts, and osteoblasts move into the area
release collagen, cartilage, and spongy bone
What is the third stage of bone repair?
bony callus
osteoblasts slowly make spongy bone that replaces fibrocartilage
spongy bone lacks strength, therefore excessive bone is formed
bone remodeling follows - osteoclasts remove excessive bone tissue restoring bone tissue much like the original
What is intramembranous ossification simply described as?
the formation of bone from fibrous connective tissue
What type of bones are forms through intramembranous ossification?
flat bones of the skull
clavicle
axial ribs
Describe the process of intramembranous ossification?
mesenchymal cells of the fibrous connective tissue turn into osteoblasts
osteoblasts secrete bone matrix
trapped osteoblasts become osteocytes
spongy bone is formed
the process of differentiation of mesenchymal cells continues on the outer surfaces of the bone
new osteoblasts and osteocytes cannot penetrate into the center because of mineralization of the matrix
compact bone is formed on the surface
What is endochondral ossification simply described as?
cartilage is substituted by the bone
this is the process associated with fetal bone development, day-to-day bone growth, and fracture repair
What bones are formed through endochondral ossification?
long bones such as
femur
humerus
Describe the process of endochonral ossification
mesenchymal cells turn into chondroblasts
chondroblasts generate hyaline cartilage
a cartilaginous cast of the bone is formed
in the diaphysis of the future bone, cartilage is substituted by the osseous tissue and the primary ossification center forms
secondary ossification centers appear in the epiphyses of the forming bone
epiphyses ossify
an avascular band of hyaline cartilage, the epiphyseal plate, forms between the two centers
this allows bone to grow in length
When do epiphyseal plates close? What does this mean for growth?
18 for females
21 for males
this means bones cannot elongate after that age
How do bones grow in length?
bone growth in length is due to the epiphyseal plate
cartilage on the epiphyseal side continues to grow (growth zone)
as new layers are formed, older cartilage layers get closer to the diaphysis (transformation zone)
eventually they become ossifies (ossification zone)
bone elongates
How is bone length growth regulated?
Groth hormone
low levels of GH can lead to dwarfism
How do bones grow in width?
bone thickness varies during the life of an individual based on the stress placed on the osseous tissue
increase in thickness is due to periosteal ossification (growth by opposition)
this process is similar to bone remodeling
What is synarthrosis?
joins the bones that do not move at all
this is a fibrous type of atriculation
bones are held together by dense irregular connective tissue
there are three types: gamphosis, suture, and syndesmosis
What is gamphosis?
A type of synathrosis
con peg and socket joint
tooth joint to jaw
What is a suture?
synthrosis example
a thing layer of dense fibrous connective tissue that connects bones of the skull
provides no motion between the bones, but allows bones to grow
What is syndesmosis?
a joint in which fibrous ligament connects the bones and allows limited amount of motion
ex: tibio-fibular articulations
What is amphiarthrosis?
provides limited motion between bones
cartilaginous type of articulation
bones are lined and held together by cartilage
ex: epiphyseal plates, rib-sternum joint, intervertebral articulations, and the symphysis pubis
What is diarthrosis?
aka synovial
joins bones that move a lot
joints have synovial cavity, articular capsule, synovial fluid
What is a synovial cavity?
space between the bones
What is an articular capsule?
consists of fibrous capsule, outer layer, that provides strength
has synovial capsule which produces the synovial fluid and contains proprioceptors and bursae
What are bursae?
extensions of the synovial membrane that makes a sack where ligaments, tendons, and bone run on each other
contain synovial fluid to decrease friction
What does the synovial fluid do?
lubricates the joints
provides nutrients to chondrocytes
remove waste products
reduces stress
What are bones in diarthrosis lined with?
hyaline cartilage which covers but does not bind the bones
also absorbs compression
What contributes to stability of diarthrosis?
articular capsule articular surface ligaments tendons bursae
Where are the ligaments in diarthrosis?
can be capsular, intracapsular, and extracapsular
contain proprioceptors
Describe a gliding joint
the articular surface is flat, allowing a slight gliding motion
found in: sternum and clavicle
scapula and clavicle
carpal and tarsal bones
Describe a hinge joint
occur where the convex surface of one bone fits into the concave surface of another bone
allows flexion and extension
found between: humerus and ulna
tibia and femur
Describe a pivot joint
characterized by the pointed surface of one bone articulating with a ring formed by bone and cartilage
allows pronation and supination
found between: radius and ulna
atlas and axis vertebrae
Describe ellipsoidal joint
oval shaped end of one bone fits into an oval-shaped cavity in another bound
allows flexion, extension, abduction, adduction
found between: bones of the wrist
radius and carpals
metacarpals and phalanges
Describe saddle joints
both articulating surfaces are saddle shaped, but one surface is concave and the other is convex
this joint is only found in apes
only found between metacarpal of thumb and trapezium
allows flexion, extension, abduction, adduction, circumduction, and slight rotation
Describe ball and socket joints
consists of a ball-like protrusion of one bone fitting into a rounded socket formed by another bone allows all movement examples: shoulder joint (between scapula and humerus) hip joint (femur and hip bones)
Simply describe skeletal muscles
associated with the bony skeleton
consist of large striated cells
all skeletal muscles are controlled voluntarily by the somatic nervous system
What are the four properties of muscle?
excitability - ability to receive and respond to a stimulus
contractibility - ability to generate force as it shortens
extensibility - ability to be stretched
elasticity - ability to return to its original shape after contraction or extension
What are the functions of muscle?
movement - muscles act on the bones of the skeleton, they are responsible for pumping blood and propelling substances through hollow organs
maintaining posture - muscles adjust the position of the body with respect to gravity
stabilizing joints - muscles exert tension around the joint
thermoregulation - muscles generate heat i.e. shivering
Describe the anatomy of muscle
it is stretched between two bones
origin is attached to an immovable bone
insertion is attached to a movable bone
Describe muscle attachments to bones
may be direct when epimysium is fused with periosteum
may be indirect when a muscle is attached via tendon or aponeurosis
What is the hierarchy of a muscle, starting at the smallest point?
muscle fibers (cells) endomysium surrounds muscle fiber fascicle is group of cells perimysium surrounds fascicles epimysium encases entire muscle (groups of fascicles)
What is the neuromuscular junction?
the connection between an axon terminal and a muscle fiber
each muscle cell is electrically isolated and is stimulated via individual neuromuscular junction
What happens at neuromuscular junction?
neurons release the neurotransmitter achetylcholine (Ach) to stimulate myocytes
each muscle cell is electrically isolated and is stimulated via individual neuromuscular junctions
What is sarcoplasm?
cytoplasm of muscle cells
contains myoglobin and mitochondria
What is the sarcolemma?
the cell membrane of muscle cells
What are T-tubules?
transverse tubules
infoldings of the sarcolemma
conduct electrical impulses from the surface of the cell to the terminal cisternae
What are myofibrils?
the contractile elements (cystoskeleton) of the muscle cell
account for ~80% of cell volume
Describe the sarcoplasmic reticulum?
smooth endoplasmic reticulum of a muscle cell that surrounds each myofibril
stores Ca2+
What do myofibrils consist of?
thick filaments (mostly myosin)
thin filaments that contain actin, tropomyosin, and troponin
actin - forms cross-bridges with myosin
tropomyosin - the backbone
troponin - activates and deactivates actin
What is the hierarchy of muscle anatomy from large to small?
Muscle fascicle muscle fiber myofibril myofilament
How are myofilaments arranged?
in a parallel manner with areas of overlap between the thick and thin filaments
What is a sarcomere?
a repeating segment of a myofibril stretched between the adjacent z-lines
How are sarcomeres organized?
H-zone - thick filaments only with no overlap
A-band - the entire lentgth of thick filaments with or without overlap
I-band - thin filaments only
M- anchors thick filaments
Z - connects thin filaments
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