Chapter 7: Skeletal System
What roles do sex hormones play in bone growth?
-They stimulate growth at the epiphyseal plate and therefore long bone growth. -They stimulate closure of the epiphyseal plate and therefore stop long bone growth.
Place the following steps of endochondral ossification in order as they would occur, starting at the top.
1. Hyaline cartilage model forms. 2. Cartilage tissue breaks down. 3. Osteoblasts form spongy and compact bone. 4. Osteoblasts become osteocytes.
Bone remodeling occurs continually as ______ reabsorb bone tissue and ______ replace the bone. The total mass of bone remains nearly constant.
1. Osteoclasts 2. Osteoblasts
Place the layers of the epiphyseal plate in order, starting with the zone closest to the epiphysis at the top.
1. Zone of resting cartilage. 2. Zone of proliferating cartilage. 3. Zone of hypertrophic cartilage. 4. Zone of calcified cartilage.
Place in order the sequence of events during the process of healing of fractures, starting at the top.
1. hematoma formation 2. fibrocartilage formation 3. bony callus formation 4. bone remodeling by osteoclasts
How many distinct layers form an epiphyseal plate?
4 layers
Vitamin ______ is necessary for osteoblast activity and vitamin ______ is necessary for collagen synthesis.
A ; C
What are the characteristics of an epiphyseal plate?
It separates the diaphysis and the epiphysis of long bones. It consists of cartilaginous cells. It is responsible for the growth in length of long bones.
What happens when the epiphyseal plate is ossified?
Lengthening of the bone is no longer possible.
Cells that deposit and form new bone during osteogenesis are called ___________.
Osteoblasts
How does a long bone grow in width?
Osteoblasts deposit new bone under the periosteum of the diaphysis.
When osteoblasts completely surround themselves with the extracellular matrix, they become cells called ____________.
Osteocytes
In a closed bone fracture, the ______ is unbroken. In a compound fracture, it is broken.
Skin
During endochondral ossification, how are spongy and compact bone deposited?
Spongy bone is formed first and compact bone is deposited between the spongy bone and the periosteum.
Match the layers of the epiphyseal plate with the appropriate description.
Zone of resting cartilage ---> Layer closest to the epiphysis Zone of proliferating ------> Young cells undergoing mitosis Zone of hypertrophic cartilage ------> Cartilage cells enlarging while osteoblasts deposit bone matrix Zone of calcified cartilage -------> Composed of dead cartilage cells encased in bone matrix.
What is a fracture?
a broken bone.
Osteopenia is a disorder characterized as ______.
a milder form of osteoporosis
In order to break down bone, osteoclasts secrete ______ to dissolve the inorganic components of a calcified bone matrix and use their ______ to digest the organic components.
acid; lysosomal enzymes
The disorder called __________, in which the hands, feet, and jaw enlarge is caused by excess growth hormone secretion in adults.
acromegaly
What disorder is characterized by enlarged hands, feet, and jaw and is caused by excess growth hormone secretion in adulthood?
acromegaly
As endochondral ossification begins, where does bone tissue first begin to replace hyaline cartilage?
center of the 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
Indicate three proteins found in bone
collagen osteocalcin osteonectin
Although about 90% of the protein found in bone is ______ other proteins exist in bone, such as ______.
collagen; osteocalcin
Osteoblasts function to ______, while osteoclasts ______.
deposit bony matrix; dissolve bony matrix
What is ossification?
formation of bone
The clinical term for a broken bone is a(n) _________ .
fracture
Osteoporosis is characterized by ______.
fragile bones that fracture easily
How do intramembranous bones form?
from sheetlike layers of unspecialized connective tissue
Excess growth hormone in childhood causes ______.
gigantism
Gigantism is caused by excess human _______ hormone in childhood.
growth (hormone)
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 are formed from models made of __________ cartilage.
hyaline cartilage
Endochondral bones develop from masses of what tissue?
hyaline cartilage
In endochondral ossification, as masses of ______ cartilage breaks down, ______ deposit bone in the spaces created.
hyaline; osteoblasts
Osteoclasts secrete acid to dissolve the ______ components of bone and use lysosomal enzymes to digest the ______ components of bone.
inorganic; organic
Flat bones in the skull develop through a process called ______ ossification.
intramembranous
Flat bones in the skull develop through a process called ______ ossification. Multiple choice question.
intramembranous
Flat bones, such as bones of the skull, that develop from sheetlike layers of connective tissue, are called ______.
intramembranous bones
The process of bone formation from membranelike layers of connective tissue is called ______.
intramembranous ossification
Some bones develop within sheetlike layers of connective tissue, and they are called ______ bones. Other bones develop from a model of hyaline cartilage and are called ______ bones.
intramembranous; endochondral
Which of the statements following accurately describes osteoblasts?
mesenchymal cells that have differentiated into bone-forming cells
Select three factors that affect bone development, growth, and repair.
nutrition hormones physical exercise
Thyroxine stimulates _______ activity, which aids in bone development and growth.
osteoblast or osteoblasts
The cells that deposit new bone tissue are the ______.
osteoblasts
Thyroxine stimulates ________ activity, which aids in bone development and growth.
osteoblasts
During ossification, ______ deposit bony matrix around themselves, ultimately surrounding themselves with bone. Once surrounded by bone, these cells are called ______.
osteoblasts; osteocytes
Cells called ________ are responsible for the break down of the calcified extracellular matrix in bone.
osteoclasts
The ______ are cells that dissolve the inorganic components of the calcified bone matrix.
osteoclasts
Parathyroid hormone stimulates bone cells called _______ , which break down bone.
osteoclasts or osteoclast
A disorder of the bones that is similar to osteoporosis, only milder, is ______.
osteopenia
In _________ , bone mass declines, bones easily fracture, and may spontaneously break because they no longer can support body weight.
osteoporosis or osteopenia
In __________, bone mass declines, bones easily fracture, and may spontaneously break because they no longer can support body weight.
osteoporosis or osteopenia
Which hormone stimulates osteoclast activity?
parathyroid hormone
Choose all glands which secrete hormones that can affect bone growth and development.
pituitary parathyroid thyroid
The total mass of bone tissue in a healthy adult skeleton ______.
remains nearly constant
Regions of the epiphyses, where cartilage slowly breaks down and spongy bone form in all directions, are called ______ ________ centers.
secondary ossification
During endochondral ossification in the epiphyses, a ______ ossification center forms, and ______ bone is formed in all directions from this location.
secondary; spongy
What are examples of bones that form through intramembranous ossification?
sternum mandible (jaw bone) flat bones of the skull
Sex hormones stimulate the formation of bone tissue during puberty; they also stimulate ossification of the epiphyseal plate and therefore they ______ bone lengthening.
stop
The term ossification refers to ______.
the formation of bones
Physical stress caused by exercise stimulates bones to grow and become ______, whereas lack of exercise causes bones to become ______.
thicker; thinner
Which of the following is a hormone that stimulates osteoblasts at the epiphyseal plate?
thyroxine
True or false: Estrogens have a stronger effect on the epiphyseal plates than testosterone.
true
In order for a long bone to grow in width (thickness), new bone is deposited ______ while the bone is eroded ______.
under the periosteum; in the medullary cavity
Vitamin _________ is necessary for the proper absorption of calcium by the body and thus is vital for proper bone formation.
vitamin D
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; calcium
What is the role of vitamin D in bone development?
Vitamin D increases calcium absorption in the small intestine and thus helps maintain the calcium concentrations necessary to build the bone matrix.
When does a long bone stop growing in length?
Bones no longer grow in length when the epiphyseal plates ossify completely.
The steps of bone remodeling are as follows: _________ formation, fibrocartilage formation, bony callus formation, and finally bone remodeling by ______ (cells).
Blank 1: hematoma Blank 2: osteoclasts
Cells called ______ dissolve bony matrix, while cells called _______ deposit new matrix.
Blank 1: osteoclasts Blank 2: osteoblasts
Cells called _______ dissolve bony matrix, while cells called ______ deposit new matrix.
Blank 1: osteoclasts Blank 2: osteoblasts
Regions of the epiphyses, where cartilage slowly breaks down and spongy bone form in all directions, are called ___________. _____________ centers.
Blank 1: secondary Blank 2: ossification
After bones have formed via intramembranous or endochondral ossification, what happens to the bone?
Bone is continually remodeled by osteoclasts and osteoblasts.
True or false: Once bone is built in childhood, it never changes.
False
How does the integumentary system interact with the skeletal system?
The integumentary system functions in the activation of vitamin D.
What is the function of osteoclasts?
To break down the calcified matrix of bones
True or false: When the ossification center of the diaphysis and epiphysis meet and the epiphyseal plates ossify, lengthening of the bone is no longer possible.
True
Match the vitamin with its role in bone development.
Vitamin A ----------> osteoblast and osteoclast activity. Vitamin C -----------> collagen synthesis. Vitamin D ------------> calcium absorption.
During the process of endochondral ossification, a primary ossification center appears in the ______, whereas secondary ossification centers appear in the ______.
diaphysis; epiphyses
Based on the way they develop, most bones in the body are ___________ bones.
endochondral
Most bones of the body are ______ bones.
endochondral
Growth hormone stimulates cell division at the ______.
epiphyseal plate
The junction between the diaphysis and epiphysis is called the ______.
epiphyseal plate
What is the name of the structure located between the primary and secondary ossification centers?
epiphyseal plate
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; testosterone
True or false: Bones of athletes are usually thinner and weaker than those of nonathletes.
false
True or false: Most bones of the skeleton are intramembranous bones.
false
