Chapter 7 skeletal system
Muscle fibers generally only have one motor end plate, but motor neurons innervate many different muscle fibers in a group. Choose the statement that correctly explains how this affects muscle contraction.
A signal traveling through one motor neuron can potentially make multiple fibers in a group contract, generating more force.
Which disorder is characterized by enlarged hands, feet, and jaw and is caused by excess growth hormone secretion in adulthood
Acromegaly
Which statement describes the mechanism of muscle contraction?
Actin filaments slide along myosin filaments.
After bones have formed via intramembranous or endochondral ossification, what happens to the bone?
Bone is continually remodeled by osteoclasts and osteoblasts.
There are 2 major glands that play a role in bone homeostasis. Thyroid glands secrete ___, while parathyroid glands secrete
Calcitonin which works with osteoblasts; PTH which works osteoclasts
During the process of endochondral ossification a primary ossification center appears in the
Diaphysis
Why are athletes typically able to exercise longer before developing muscle fatigue than non-athletes?
Due to training, athletes have a better blood supply and more mitochondria in their muscles than do non-athletes.
A band of cartilage that allows for the growth in length of an endochondral bone is called
Epiphyseal plate
The term ossification refers to
Formation of bone
How do intramembranous bones form?
From sheetlike layers of unspecialized connective tissue
process of healing a fracture
Hematoma formation, fibrocartilage formation, bony callus formation, bone remodeling by osteoclasts
Endochondral bones are formed from models made of
Hyaline cartilage
Endochondral bones develop from what masses of what tissue
Hyaline cartilage
Which of the following is not a step in endochondral bone formation
Hyaline cartilage changes to adipose tissue.
Endochondral ossification in order
Hyaline cartilage model forms, cartilage tissue breaks down, osteoblasts form spongy and compartment bone, osteoblasts become osteocytes
What is the process by which a bone grows in length
Increased activity within the epiphyseal plate
Bones that develop with sheets of connective tissue are called
Intramembranous bones
Flat bones in the skull develop through a process called
Intramembranous ossification
The process of bone formation from membrane like layers of connective tissue is called
Intramembranous ossification
The process of bone formation from membrane like layers of connective tissues is called
Intramembranous ossification
Which of the following does not describe the functions of the skeletal system
It generates the movements of the limbs.
Indicate the statements that are true about intramembranous ossification
It occurs between flat sheets of CT, and skull bones are formed via intramembranous ossification
What happens when the epiphyseal plate is ossified?
Lengthening of the bone is no longer possible.
How long does a bone grow in width?
Osteoblasts deposit new bone under the periosteum of the diaphysis
Cells that are responsible for the breakdown of the calcified extracellular matrix in bone
Osteoclasts
When osteoblasts completely surround themselves with the extracellular matrix, they become cells callled
Osteocytes
Glands that secrete hormones that affect bone growth and development
Pituitary, thyroid, parathyroid
What is the function of osteoblasts
Production of bone
Regions of the epiphyses, where cartilage slowly breaks down and spongy bone form in all directions called
Secondary ossification
How does the integumentary system interact with the skeletal system
The integumentary system functions in the activation of vitamin D.
Certain natural plant poisons and animal venoms contain substances that inhibit the function of acetylcholinesterase. If a person is poisoned by one of these substances, which of the following will be the cause of their symptoms?
Their muscles won't be able to contract because acetylcholine will be attacked and degraded immediately after release from the neuron.
What roles do sex hormones play in bone growth?
They stimulate closure of the epiphyseal plate and therefore stop long bone growth. They stimulate growth at the epiphyseal plate and therefore long bone growth.
Hormone that stimulates osteoblasts at the epiphyseal plate?
Thyroxine
What is the action of the thyroid hormone thyroxine on the skeletal system
To stimulate replacement of cartilage with bone in the epiphyseal plate.
What is the role of Vitamin D bone development?
Vitamin D increases calcium absorption in the small intestine and thus helps maintain the calcium concentrations necessary to build the bone matrix
In order to break down bone osteoclasts secrete ___ to dissolve the inorganic components of calcified bone matrix and use their ___ to digest the organic components
acid and lysosomal enzymes
The ___ secretes___, which promotes Na+ and water retention
adrenal cortex; aldosterone
A bone thickens
as compact bone is deposited beneath the periosteum of the diaphysis.
What are fascicles?
bundles of muscle fibers
As endochondral ossification begins, where does bone tissue first begin to replace hyaline cartilage?
center of diaphysis
With a(n) ___ fracture, the skin remains intact. With a(n) ___ fracture, the skin is damaged and the bone is exposed with an increased risk of infection
closed, open
Although about 90% of the protein found in bone is ___ other proteins exist in bone, such as __
collagen and osteocalcin
Bones that develop from masses of hyaline cartilage are called
endochondral bones
most bones of the body are
endochondral bones
Growth hormone stimulates cell division at the
epiphyseal plate
What is the name of the structure located between the primary and secondary ossification centers?
epiphyseal plate
Secondary ossification centers appear in the
epiphyses
The hormone ___ has a stronger effect than ___ on the epiphyseal plate, causing it to close more quickly. This explains the discrepancy in height between male and female adults
estrogen and testosterone
The clinical term for a broken bone is
fracture
Excess growth hormone in childhood causes
gigantism
Which hormone stimulates growth at the epiphyseal plate?
growth hormone
What helps control the opposing processes of resorption and deposition of the bone matrix?
hormones
Which is a factor that directly influences bone development, growth, and repair
hormones
Endochondral bones develop from masses of what tissue?
hyaline cartilage
In endochondral ossification, as masses of ___ cartilage breaks down, ___ deposit bone in spaces created
hyaline; osteoblasts
Osteoclasts secrete acid to dissolve the ___ components of bone and use lysosomal enzymes to digest the ___ components of bone
inorganic and organic
Flat bones, such as bones of the skull, that develop from sheetlike layers of connective tissue, are called ______.
intramembranous bones
During strenuous exercise, when muscles are not being supplied with enough oxygen, a shift in metabolism results in the breakdown of pyruvic acid to lactic acid. What is this change in metabolism called?
lactic acid threshold
Which of the statements following accurately describes osteoblasts?
mesenchymal cells that have differentiated into bone-forming cells
The formation of bone is called
ossification
Cells that deposit and form new bone during osteogenesis are called
osteoblasts
Which of the following bone cells would have the greatest number of lysosomes?
osteoclasts
3 proteins found in bone
osteonectin, osteocalcin, collagen
A disorder of the bones that is similar to osteoporosis, only milder, is ______.
osteopenia
Which hormone stimulates osteoclast activity
parathyroid hormone
intramembranous ossification
process by which bone forms directly from mesenchymal tissue
endochondral ossification
process in which bone forms by replacing hyaline cartilage
Red bone marrow functions in the formation of
red blood cells, white blood cells, platelets
The total mass of bone tissue in a healthy adult skeleton
remains nearly constant
In skeletal muscle fibers, what is the source of the calcium ions that are released into the sarcoplasm to bind with troponin, resulting in contraction?
sarcoplasmic reticulum
During endochondral ossification in the epiphyses, a ___ ossification center forms, and ___ bone is formed in all directions from this location
secondary; spongy
In a closed bone fracture, the ___ is unbroken. In a compound fracture, it is broken
skin
What are examples of bones that form through intramembranous ossification?
sternum mandible (jaw bone) flat bones of the skull
What is the function of creatine phosphate?
supplies energy for the synthesis of ATP
In order for a long bone to grow width (thickness), new bone is deposited ____ while the bone is eroded ____
under the periosteum; in the medullary cavity
UV radiation striking skin is a step in activating ____, which then plays a role in absorption and availability of ___ for use in forming the bone matrix
vitamin D and calcium
At what age are nearly all bones completely ossified?
25 years old
How many distinct layers form an epiphyseal plate?
4 layers
Vitamin __ is necessary for osteoblast activity and vitamin __ is necessary for collagen synthesis
A and C