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How bones grow in length

The epiphyseal plate is the area of growth in a long bone. It is a layer of hyaline cartilage where ossification occurs in immature bones. On the epiphyseal side of the epiphyseal plate, cartilage is formed. On the diaphyseal side, cartilage is ossified, and the diaphysis grows in length. The epiphyseal plate is composed of four zones of cells and activity ( [link] ). The reserve zone    is the region closest to the epiphyseal end of the plate and contains small chondrocytes within the matrix. These chondrocytes do not participate in bone growth but secure the epiphyseal plate to the osseous tissue of the epiphysis.

Longitudinal bone growth

This illustration shows the zones bordering the epiphyseal plate of the epiphysis. The topmost layer of the epiphysis is the reserve zone, which is colored blue because it is made of cartilage. Two arteries are shown travelling through this zone to supply nutrients to the second zone: the proliferative zone. Here, five chondrocytes are undergoing mitosis. They continually divide, producing five long rows of chondrocytes. The next zone is the zone of maturation and hypertrophy. Here, lipids, glycogen and alkaline phosphatase accumulate, causing the cartilaginous matrix to calcify. This zone consists of five rows of ten chondrocytes which are increasing in size as one moves down a row. The next zone is the calcified matrix. Here, the chondrocytes have hardened and die as the matrix around them has calcified. The bottommost row is the zone of ossification. This zone is actually part of the metaphysis. Arteries from the metaphysis branch through the newly-formed trabeculae in this zone. The newly deposited bone tissue at the top of the zone of ossification is called the primary spongiosa. The older bone at the bottom of the zone of ossification is labeled the secondary spongiosa.
The epiphyseal plate is responsible for longitudinal bone growth.

The proliferative zone    is the next layer toward the diaphysis and contains stacks of slightly larger chondrocytes. It makes new chondrocytes (via mitosis) to replace those that die at the diaphyseal end of the plate. Chondrocytes in the next layer, the zone of maturation and hypertrophy    , are older and larger than those in the proliferative zone. The more mature cells are situated closer to the diaphyseal end of the plate. The longitudinal growth of bone is a result of cellular division in the proliferative zone and the maturation of cells in the zone of maturation and hypertrophy.

Most of the chondrocytes in the zone of calcified matrix    , the zone closest to the diaphysis, are dead because the matrix around them has calcified. Capillaries and osteoblasts from the diaphysis penetrate this zone, and the osteoblasts secrete bone tissue on the remaining calcified cartilage. Thus, the zone of calcified matrix connects the epiphyseal plate to the diaphysis. A bone grows in length when osseous tissue is added to the diaphysis.

Bones continue to grow in length until early adulthood. The rate of growth is controlled by hormones, which will be discussed later. When the chondrocytes in the epiphyseal plate cease their proliferation and bone replaces the cartilage, longitudinal growth stops. All that remains of the epiphyseal plate is the epiphyseal line    ( [link] ).

Progression from epiphyseal plate to epiphyseal line

This illustration shows anterior views of a right and left femur. The left femur possesses a growth plate at the border of its distal metaphysis and distal epiphysis. The proximal epiphysis has two growth plates. The first is located below the head of the femur while the second is located below the trochanter, which is the bump on the lateral side of the femur. The right femur has the same plates as the left femur. However, the left femur represents a mature long bone. Here, growth is completed and the epiphyseal plate has degraded to a thin, faint, epiphyseal line.
As a bone matures, the epiphyseal plate progresses to an epiphyseal line. (a) Epiphyseal plates are visible in a growing bone. (b) Epiphyseal lines are the remnants of epiphyseal plates in a mature bone.

How bones grow in diameter

While bones are increasing in length, they are also increasing in diameter; growth in diameter can continue even after longitudinal growth ceases. This is called appositional growth. Osteoclasts resorb old bone that lines the medullary cavity, while osteoblasts, via intramembranous ossification, produce new bone tissue beneath the periosteum. The erosion of old bone along the medullary cavity and the deposition of new bone beneath the periosteum not only increase the diameter of the diaphysis but also increase the diameter of the medullary cavity. This process is called modeling    .

Bone remodeling

The process in which matrix is resorbed on one surface of a bone and deposited on another is known as bone modeling. Modeling primarily takes place during a bone’s growth. However, in adult life, bone undergoes remodeling    , in which resorption of old or damaged bone takes place on the same surface where osteoblasts lay new bone to replace that which is resorbed. Injury, exercise, and other activities lead to remodeling. Those influences are discussed later in the chapter, but even without injury or exercise, about 5 to 10 percent of the skeleton is remodeled annually just by destroying old bone and renewing it with fresh bone.

Diseases of the…

Skeletal system

Osteogenesis imperfecta (OI) is a genetic disease in which bones do not form properly and therefore are fragile and break easily. It is also called brittle bone disease. The disease is present from birth and affects a person throughout life.

The genetic mutation that causes OI affects the body’s production of collagen, one of the critical components of bone matrix. The severity of the disease can range from mild to severe. Those with the most severe forms of the disease sustain many more fractures than those with a mild form. Frequent and multiple fractures typically lead to bone deformities and short stature. Bowing of the long bones and curvature of the spine are also common in people afflicted with OI. Curvature of the spine makes breathing difficult because the lungs are compressed.

Because collagen is such an important structural protein in many parts of the body, people with OI may also experience fragile skin, weak muscles, loose joints, easy bruising, frequent nosebleeds, brittle teeth, blue sclera, and hearing loss. There is no known cure for OI. Treatment focuses on helping the person retain as much independence as possible while minimizing fractures and maximizing mobility. Toward that end, safe exercises, like swimming, in which the body is less likely to experience collisions or compressive forces, are recommended. Braces to support legs, ankles, knees, and wrists are used as needed. Canes, walkers, or wheelchairs can also help compensate for weaknesses.

When bones do break, casts, splints, or wraps are used. In some cases, metal rods may be surgically implanted into the long bones of the arms and legs. Research is currently being conducted on using bisphosphonates to treat OI. Smoking and being overweight are especially risky in people with OI, since smoking is known to weaken bones, and extra body weight puts additional stress on the bones.

Watch this video to see how a bone grows.

Chapter review

All bone formation is a replacement process. Embryos develop a cartilaginous skeleton and various membranes. During development, these are replaced by bone during the ossification process. In intramembranous ossification, bone develops directly from sheets of mesenchymal connective tissue. In endochondral ossification, bone develops by replacing hyaline cartilage. Activity in the epiphyseal plate enables bones to grow in length. Modeling allows bones to grow in diameter. Remodeling occurs as bone is resorbed and replaced by new bone. Osteogenesis imperfecta is a genetic disease in which collagen production is altered, resulting in fragile, brittle bones.

Questions & Answers

human body largest organ.....
jasveer Reply
liver
JOY
liver
Lem
Skin
amen
lungs
Zamiir
liver and skin
Marina
skin
brian
by mass is liver but externally is de skin
Kumsah
all answers Are correct
brian
no
Rehman
liver is the largest gland of the body but skin is the largest organ of the body
Rehman
so please what is the answer now
Marina
afcous skin.because difference between Gland and organ
Safiya
Only the skin
Williams
The largest organ is the skin and the liver is a gland
Williams
skin is the largest organ of the body
Denis
liver
julie
it's the skin
trinna
skin 100%
Mallikharjun
largest organ- liver largest system- Skin
Shahriar
largest organ is skin because it covers the rest of the organs
Syed
liver right answers
nisha
liver
Justine
skin
Areej
liver is largest gland
Areej
skin is largest organ liver is largest gland femur is largest bone thyroid gland is largest endocrine gland seratus muscle is largest muscle
Tanveer
sciatic nerve is largest nerve
Tanveer
portal vein is largest vein
Tanveer
GIT is largest tube in body
Tanveer
explain about cerebrum cereblum and pons medulla
Tanveer
Nervous system anotomy and physiology
Tanveer
skin is the human body's largest organ
Kimbley
@Tanveer, the cerebrum consists of the cerebral cortex, corpus callosum, hippocampus, and basal ganglia. The cerebellum is located inferior to the occipital lobe. The pons and medulla are part of the lower brainstem.
Carmelo
The cerebral cortex are divided into 4 lobes and control functions such as: thinking, learning, speech, sensory perception, motor functions, hearing and vision, etc. The cerebral cortex is mainly present only in mammals due to evolution. The hippocampus plays a main role in memory formation.
Carmelo
The cerebellum works together with the motor cortex and other parts of the brain to coordinate and fine tune muscular activity. The pons and medulla control autonomic functions such as: sleep, respiration, swallowing, vomiting, heart rate, vasomotor control and more other things.
Carmelo
skin hai friend
Tilak
define homeostasis and explain it's importants
Adusei Reply
define the important life processes of humans
Adusei
how the bone marrow transplantation is done?
Tanveer
what is homeostasis
julie Reply
internal temperature of body
Sanket
Homeostasis is the internal constancy in which your body tries to maintain for optimal cellular functioning. For example, your body tries to maintain an internal body temperature of about 98.6F for optimal functioning of your body.
Carmelo
If a prolonged lost of homeostasis occurs, death of the organism will be the outcome.
Carmelo
Another example of homeostasis is that your body tries to maintain a specific blood sugar level, so that your cells can undergo constant cellular respiration and keep you alive.
Carmelo
homeostasis is the fairly constant internal changes of an environment (your internal environment).The temperature of a body must be kept between the range of 37.5°c
raphael
which tissue is more sensitive
Rit Reply
to what?
Lari
explain types of hypertension
Juli Reply
What is bulbar paralysis?
Roshni Reply
how can make penis larger
Marwat Reply
what is the stimuli initiates the control of erythropoiesis?
Ok Reply
oxygen
Liyungu
Erythropoietin, a hormone synthesized and released by the kidneys stimulate erythropoiesis in red bone marrow. When an Individual loses blood (hemorrhage) and the concentration of RBCs or oxygen decreases, erythropoitein will be released.
Carmelo
how lymph is from
Hafsa Reply
Lymph is essentially interstitial fluid that ends up in the lymphatic vessels that didn't go back into the venules. Lymph is composed of the same components as your blood plasma which contains water, solutes, oxygen, CO2, foreign particles such as toxins, bacteria and viruses.
Carmelo
what is the cause of twins
Clarus
The cause of identical twins is when a single fertilized egg undergo mitosis (splits in two) . As a result, both eggs now have the same genetic information, therefore producing two identical twins.
Carmelo
how structure and function relate to each other?
Garmai
This is a very important rule in Anatomy and Physiology. The structure of a cell, tissue, or organ will tell you a lot about it's function.
Carmelo
For example, simple columnar cells (enterocytes) in the villus present in the duodenum of the small intestine contain microvilli. Microvilli are finger like projections of the cell membrane (produce by the cytoskeleton)that increase the surface area for absorption of nutrients into the enterocytes.
Carmelo
The main role of these enterocytes is to absorb. Therefore, having Microvilli as a structure relates to its function.
Carmelo
@ Carmelo thanks for the answer.
Garmai
welcome
Carmelo
what is anatomy
Kamran Reply
is simply defined as the stody of internal and external structure of human body and the relationships between the body part.
Surajo
Anatomy Is The Study Of The Structure Of The Human body
Dennis
anatomy is the science that deals with the study of the body structure
Vida
what is stress hyperglycaemia and Pathophysiology
amani
Hyperglycemia is the term used when somebody is in a state of high blood sugar levels. For example, after you eat a meal with carbohydrates in it, (post-absorbptive state) your blood is hyperglycemic.
Carmelo
Pathophysiology is the study of how diseases function and cause abnormal functioning in the body. Usually pathophysiology is studied at a molecular/cellular level.
Carmelo
I meant to say absorbptive* state on explanation of hyperglycemia. Usually during post-absorbptive state your blood has low blood sugar levels.
Carmelo
what is sex?
Soumyakanta Reply
Your biological sex is determined by your sex chromosome which is pair number 23. if you have a XX pair then you are a female. if you have XY pair then you are a male.
Carmelo
the sex chromosomes are called as allosome
Tanveer
True, the other 22 pairs are called autosomes :)
Carmelo
why the left hemisphere controls the right side body parts and right hemisphere controls the left side body parts?
Tanveer
because it is like that
Sherin
It has to do with how the neuronal pathway are intertwined to opposites sides of the body I think. A motor output from the left cerebral hemisphere (motor cortex) will end up stimulating your right side of the body.
Carmelo
brother Carmelo don't miander, sex ,it just the state of being a male or female
Liyungu
Your biological sex is tied to your DNA (genetic information). A male have testes and female have ovaries which are reproductive organs is tied to your genetic information (sex chromosome). If an individual feels like it is either a male or female is called gender identity.
Carmelo
thanks our beloved brother Carmelo
Liyungu
that's great learning something everyday
Tasheria
what is anatomy
Rohino
most blood enters the ventricle during what phase?
Tina Reply
rapid ejection
Tanveer
Most of the blood in the heart enters the ventricles during the diastolic phase.
Carmelo
ok
ren
which of the following is the types of personal protective equipment protects mucous membranes?
Garmai
Most (not all) mucous membranes secrete mucus because they contain goblet cells in between the epithelial tissue. Mucus coats the layers of epithelium and traps particles. The epithelial type is either stratified squamous, simple columnar, or pseudostratified columnar in mucous membranes.
Carmelo
Are you a professor Carmelo?
Sherin
No sir, I'm a nursing and biology student as well in university.
Carmelo
smart!
Sherin
thanks!
Carmelo
why the fever occurs if any injury or pain occurs
Tanveer
fever is de best indication to show there is an infection
Kumsah
what is the actual mechanism of fever
Tanveer
correct Tanveer, the normal internal body temperature is 98.6 Fareinheit. When the temperature rises above 100 fareinheit, it is usually an indication of infection.
Carmelo
White blood cells which protect you against foreign antigens become active and release cytokines (pyrogens) during infection which causes the hypothalamus to raise your internal body temperature.
Carmelo
thank you so much.really you are very intelligent.
Tanveer
thank you. you are very intelligent
Tanveer
the mechanism of fever appears to be a defensive reaction by the body against infectious disease. when bacteria or viruses invade the body and cause tissue injury one of de body immune system's responses is to produce pyrogen
Kumsah
Yes, the hypothalamus responds to pyrogens by raising your body temperature. The reason your hypothalamus does this is to stunt the growth and metabolism of whatever is causing the infection (bacteria, virus, fungi protozoa, etc.)
Carmelo
how the kidney transplantation is done
Tanveer
Which university are you studying?
Sherin
karnataka
Tanveer
and all of you ,university
Tanveer
Really so talented
Savita
I was asking Carmelo?
Sherin
Georgia State University.
Carmelo
oh nice! I'm in University of Texas
Sherin
nice!!!
Carmelo
vicious this is chaptare I reading 5day after
Taufik
pleas sir can u teach me
Taufik
not sure, can u help me?
Nichole
I'm in University of Technology, Jamaica
Nichole
why do you not helf me
Taufik
what difference exist between anatomy and physiology?
Collins Reply
Anatomy: study of the structure of the body parts and their relationship to one another
Shana
Physiology: Study of the function of body parts and how they work to carry out life-sustaining activities
Shana
physiology function and anatomy location
Bashir
anatomy refers to the study of the body parts and their relationship to each other while physiology deals with functioning of those body parts
Umutoni
Yes of course.In layman language Anatomy is study of internal organs, whereas physiology is study of how those organs function. Anatomy is is related to how they look their shape size... Physiology is how they work
Juveriya
anotomy dealt with the external and internal stuctural features of body and their constituent physiology deals with the functioning or action of that stucture
Tanveer
Anatomy is the study of the structures (internal and external) of a living organism. Physiology is the study of how the structures of a living organism function often at a molecular and cellular level.
Carmelo
anatomy is the structure of different body parts of human body and physiology is the normal body function of body parts of the human body
Akshay
anatomy is study of structure of the body e.g, system,organ's size shape location and physiology is the study of function of the body eg,eye ball movement , release of hormones , circulation of blood etc
Soumya
thanks
Tammy
thanks guys. I appreciate
Collins
thanks bro
SAGAR
Explain the meaning of life in a scientific manner
Dezni
probably it doesn't have a meaning yet it can be realised by certain signs that have a scientifically defined terms?!!!!
Osama
At least in a scientific manner, scientists have agreed that production and use of cellular energy, as well as growth and reproduction are essential when defining what is alive in a biological sense. For example, viruses are not considered alive because they cannot grow or reproduce by themselves.
Carmelo
this virus issues is being challenged currently.
Osama
what z your conclusion over virus bro?
Liyungu
pipo what is the relationship between T- cells ( specifically T-helper), & all three line of defence mechanism
Liyungu
anatomy is the science that deals with the study of the human structure whilst physiology is a science that covers the function and process of the body structure.
Vida
defien brache of Anatomy
Hamad
anatomy is the study of internal and external body parts while physiology is the science that covers the function and process of the body structure.
Priscillah
what is blood fluid
Adefarasin Reply
what is menstrual cycle
Adefarasin
periodic flow of blood from the female human vigina, after an unfertlized egg has been released from the ovaries
Kobby
the shedding of of the uterine walls,that occurs when fertilization doesn't occur
Kevin
fertilization after occur menstrual cycle
Bashir
it's called menses
Melissa
menses:(menstrual cycle) A monthly shedding of uterine lining and blood. For up to 3 to 7 days every 28 days.
Mel
The menstrual cycle is divided into multiple phases. Menses is the last phase of the cycle when fertilization doesn't occur and endometrium of the uterus shed (stratum functionalis) due to lack of estrogen and progesterone signaling.
Carmelo
The lack of estrogen and progesterone signaling is due to the degeneration of the corpus lueteum when fertilization doesn't occur.
Carmelo
Blood fluid: Blood is composed of blood plasma + formed elements. The blood plasma is 55% of blood volume and it contains 90% of water. It also contains ions, hormones, gases, protein transporters, etc. Blood plasma is also considered extracellular fluid.
Carmelo
The formed elements of blood include RBCs (45-50% of blood), WBCs and Plalets (less than 1% of blood).
Carmelo
Almost forgot, blood plasma also carries nutrients which is obviously very important for survival.
Carmelo
we appreciate bro, our studies are becoming easy & easy
Liyungu
what difference between zink and jesta
Anurag Reply

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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