Tuesday, May 1, 2018

Growth of a Long Bone

Basic Anatomy , Skeleton
Growth of a Long Bone

Growth of a Long Bone


All long bones of the body (except clavicle) are formed from a cartilaginous model by the process of ossification. Once a young bone is formed, the growth takes place in three steps.

Growth in length


A long bone grows in length my multiplication of cells in the epiphyseal plate of cartilage. The cartilage cells divide and increase in number. The zone of active division in the epiphyseal plate of cartilage lies towards the epiphysis (end of the bone). This means that newly formed cartilage cells will push the older, larger cells towards the diaphysis (shaft of the bone).  Eventually these cartilage cells are replaced by osteocytes (bone cells), thus increasing the length of the bone. It should be kept in mind that after puberty, when the epiphyseal plate of cartilage no more exists, the growth in length of a bone stops completely.

Growth in thickness


A long bone grows in thickness by multiplication of cells in the deeper layer of periosteum. The cells lying in the deeper layer of periosteum are known as osteoblasts (bone forming cells). These cells divide continuously and form the osteocytes, thus increase the thickness of bone.


Bone Growth

Remodeling of bone


The growth take place by deposition of new bony tissue on the surface and at the ends. The is process of bone deposition by osteoblasts is called appositional growth or surface accretion. The appositional growth can result in shape alterations, however,  in order to maintain the shape, the unwanted bone must be removed. This job is done by another class of cells known as octeoclasts. The process of reshaping the bone is called remodeling and it is one of the major factors responsible for increasing size of marrow cavity.

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Ossification of Bones

Basic Anatomy , Skeleton
Ossification of Bones

Ossification of Bones


Ossification is the process by which bone is formed. The formation of bone is in fact conversion of other types of connective tissues into bone. Based on the type of tissue converted into bone, the process of ossification is of three types. These types with appropriate detail are explained in the lines below.

Intra-membranous ossification


This type of ossification is also known as mesenchymal ossification. In this type the bone is ossified from mesenchymal condensations. The bones formed by this process of ossification are known as membranous bones or dermal bones.

Intra-cartilaginous ossification


In this type of ossification, the mesenchyme has been converted to cartilaginous models and the process of ossification starts in these cartilaginous models. The process of conversion of mesenchymal condensations in cartilage is known as chondrification and this process takes place during the second month of intrauterine life. This indicates that the bones which start ossifying before second month are membrane bones and the bones which start ossifying after 2nd month of intrauterine life are cartilaginous bones.
There is another type of ossification in which a bone partly ossifies from membrane and partly from cartilage. These bones are known as membro-cartilaginous bones.

Process of ossification


With the explanation of different types of ossification in bones it is also important to explain what ossification is. Ossification is the process by which bone is formed. It is started at certain sites known as centers of ossification each of which is a point where lying down of lamellae (bone formation) is started by the activity of osteoblasts. Osteoblasts are bone forming cells and secrete collagen and other substances that form the ground substance of bone. The centers of ossification may be primary or secondary. The primary centers of ossification appear before birth and are the first to start the process of ossification. The secondary centers of ossification mostly appear after birth but there are few exceptions to this that is some secondary centers do appear before birth. The secondary centers are sites where process of ossification starts after it has started in primary centers.3



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Types of Cells in Bone

Basic Anatomy , Skeleton
Types of Cells in Bone

Types of Cells in Bone


Bone is formed by three primary cell types: Osteoblasts, Osteocytes and Osteoclasts.

Osteoblasts


Osteoblasts are  bone-forming cells that descend from osteoprogenitor cells. They form a protein mixture known as osteoid, which mineralizes to become bone. Osteoid is primarily composed of Type I collagen. Osteoblasts also manufacture hormones, such as prostaglandins, to act on the bone itself. They robustly produce alkaline phosphatase, an enzyme that has a role in the mineralization of bone, as well as many matrix proteins. Osteoblasts are the immature bone cells, and eventually become entrapped in the bone matrix to become osteocytes, which are the mature bone cells. All bone lining cells are osteoblasts.

Osteocytes


Osteocytes are mature bone cells that originate from osteoblasts, which have migrated into and become trapped and surrounded by bone matrix, produced by themselves. The spaces they occupy are known as lacunae. Osteocytes have many processes that reach out to meet osteoblasts and other osteocytes probably for the purposes of communication. Their functions include formation of bone, maintenance of matrix and homeostasis of Calcium.

Osteoclasts


Osteoclasts are the cells responsible for bone resorption and remodelling. They are large, multinucleated cells located on bone surfaces in what are called Howship’s lacunae or resorption pits. These lacunae, or resorption pits, are left behind after the breakdown of the bone surface. Because the osteoclasts are derived from a monocyte stem-cell lineage, they are equipped with phagocytic-like mechanisms similar to circulating macrophages.


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Parts of a Young Bone

Basic Anatomy , Skeleton
Parts of a Young Bone

Parts of a Young Bone



A typical long bone, which is still young remains under the process of ossification for many years. It ossifies in three parts; the two ends and one shaft. The ends ossify from secondary centers of ossification while the shaft ossifies from primary center of ossification. Primary center of ossification is the center where the process of ossification starts first of all. Secondary centers of ossification are the centers where the process of ossification starts after the primary center.
In a young bone in which the process of ossification is not complete and the following important parts can be distinguished from the others;

  • Epiphysis
  • Diaphysis
  • Metaphyses
  • Epiphyseal plate of cartilage


Parts of a young bone

Epiphysis


The ends and the tips of a long bone that ossify from secondary centers are known as epiphyses. Epiphyses are of 4 types and they can be better understood by explaining their types;

  • Pressure epiphyses: These epiphyses are articular that is they take part in joint formation. These epiphyses are the weight transmitting epiphyses. Examples are head of the humerus, lower end of the radius etc.
  • Traction epiphyses: These are non-articular and do not take part in the formation of joints. They also do not take part in transmission of weight. The actual job of traction epiphyses is to provide attachment to tendons of muscles. The traction epiphyses ossify later than the pressure epiphyses. Examples of these epiphyses are tubercles of humerus (greater tubercle and lesser tubercle) and trochanters of femur (greater trochanter and lesser trochanter)
  • Atavistic epiphyses: These epiphyses are phylogenetically independent but they become fused in man. Examples are coracoid process of scapula and os trigonum.
  • Aberrant epiphyses: As the name indicates (aberrant = not usual) these epiphyses are not always present. Examples are epiphyses at the head of the first metacarpal bone and at the base of other metacarpal bones.

Diaphysis


Diaphysis is the term used for elongated shaft of the long bone. It ossifies from a primary center.


Metaphyses


The ends of diaphysis near the epiphyses are known as metaphyses. Since a long bone has two ends so there are two metaphyses. Each metaphysis is the zone of active growth of a long bone. Before the fusion of diaphysis and epiphyses, the metaphyses are richly supplied with blood through end arteries forming hair pin bends. This is the common site of osteomyelitis in children.

Epiphyseal plate of cartilage


This is a plate of cartilage separating epiphyses from metaphyses. The cells of this cartilage plate proliferate and are responsible for the length wise growth of a long bone. When the age of maturity arrives, this cartilage plate ossifies and then the bone can no longer grow in length. This plate of cartilage is nourished by both epiphyseal and metaphyseal arteries.

For detailed study of human bones, please visit: Basic Anatomy of Bone



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Female Reproductive System

Human Organ Systems ,
Female Reproductive System

Female Reproductive System Outline


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Internal
Parts
UterusMajor female reproductive organ,
one end called cervix opens into
vagina and other end is connected
to the fallopian tubes, Development
of fetus occurs within uterus
OvariesTwo in number, Egg producing
female reproductive organ, oval 
in shape and ovary of each side 
is locatd in the ovarian fossa of 
corresponding side of pelvis
External
Parts
VulvaExternal genital organ of females,
contains the opening of vagina
LabiaStructures of skin and adipose tissue
that extends on both sides of vulva
ClitorisButton like portion near the labia
minora, erects on sexual arousement

Functions

Recieve the sperms from male reproductive
system, Bear the developin fetus through
the entire period of gestation

Introduction to Female Reproductive System




Female reproductive system is the system of reproduction in female human beings. The female reproductive system is complex as compared to the male reproductive system. Females have to bear fetus during fetal period of development within their bodies. Modifications and adaptations to bear the fetus makes female reproductive system more complex. The female body also shows certain adaptations to become capable of bearing the fetus for nine months. Main role of female reproductive system is to produce eggs and allow the process of fertilization and development to take place within their body. The organs of female reproductive system are




Female Reproductive System

Organs of Female Reproductive System


Female reproductive system consists internal and external parts.
INTERNAL PARTS:
Internal parts are the functional parts of female reproductive system. There are two main internal parts; the uterus and the ovaries.
  • UTERUS: Uterus (also known as womb) is the major reproductive organ of females. It hosts the developing fetus, produces secretions of the female reproductive system and allow the passage of sperms to fallopian tubes where sperms fertilize with eggs.
  • OVARIES: Ovaries are small paired organs located near the pelvic cavity of females. Ovaries produce the female egg cells.
EXTERNAL PARTS:
External parts are accessory parts of female reproductive system. They help in the process of fertilization, and parturition etc. They are;


  • VULVA
  • LABIA
  • CLITORIS

Functions of Female Reproductive System


As stated above, female reproductive system is mainly concerned with production of eggs and bearing the fetus throughout the developmental phase. The ovaries produce eggs, which are fertilized by sperms and zygote is formed. The development of zygote to a complete human baby takes place in female reproductive system.
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Male Reproductive System

Human Organ Systems ,
Male Reproductive System

Male Reproductive System Outline


Components
PenisMale copulatory organ having a long
shaft and a bulbous tip, transfers the
semen into the femal reproductive tract
TestesComponents of both reproductive system
and endocrine system, produce semen
that ocntains sperms
FunctionsFertilization of females to produce offspring

Introduction of Male Reproductive System


Male reproductive system is the system of sex organs of male human beings that are a part of the overall reproductive process of human beings. Reproduction is the capacity of all living organisms to give rise to their babies that are similar to them. In human beings, sexual type of reproduction takes place and for this type of reproduction, male and female reproductive systems are required. Male reproductive system is mainly concerned with production of semen (whitish viscous fluid emitted from the male reproductive tract that contains sperm and fluids) and transferring it into the female reproductive tract.



Male Reproductive System 
(Source: Male_anatomy.png & Tsaitgaist/Wikipedia)

Organs of male Reproductive System 


The organs of male reproductive system are penis and testes. They lie outside the male’s body in the pelvic region.


  • PENIS: Penis is the external sexual organ of male human beings. It’s main role is to get access to the female reproductive system during sexual intercourse. In addition to the reproductive role, it also serves as the excretory organ through which urine is expelled out of the body.
  • TESTES: Testes are components of both reproductive and endocrine system. For reproductive system they produce sperm and for endocrine system they produce male sex hormones like testosterone.

Functions of the male Reproductive System 


As stated above, male reproductive system is mainly concerned with production of semen and its transfer to the female reproductive tract. Testes, that are organs of male reproductive system, also produce male sex hormones that distinguish maleness from femaleness. Reproduction is the process through which life continues to exist. Every individual has a limited life span and no one can survive for ever. For the survival of life, reproduction is a necessary process because otherwise no new life will be formed and old life will disappear. So both reproductive systems, whether male or female, are important for survival of life.
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Urinary System

Human Organ Systems ,
Urinary System

Urinary System Outline





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KidneysKidneys are two bean shaped organs lying
close to the lumbar spine on either side,
they are multifunction organ, form urine
and control its concentration
UretersTwo hollow muscular tubes one arising
from each kidney and ending at the urinary
bladder, connect kidneys to the bladder
Urinary
Bladder		Stores urine before it is excreted from the
body, hollow muscular and distensible
organ, sits on the pelvic floor.
UrethraA tube connecting the urinaly bladder to
the genitals for excretion
FunctionsExcretion of nitrogenous wastes, Osmoregulation,
Acid-Base balance

Introduction to Urinary System


Urinary system is also known as excretory system of human body. It is the system of production, storage and elimination of urine. Formation and elimination of urine is important for human body because urine contains nitrogenous wastes of the body that must be eliminated to maintain homeostasis. Nitrogenous wastes are formed by metabolic activities in the cells. These nitrogenous wastes along with excess of salts and water are combined in the kidneys to form urine. Urinary system is important for keeping the internal environment of the body clean. Urinary system maintains proper homeostasis of water, salts and nitrogenous wastes.



Urinary System 
(SOURCE: Jordi March i Nogué/Wikipedia)

Components of Urinary System


Human urinary system consists of two kidneys, two ureters, a urinary bladder, a urethra and sphincter muscles.
  • KIDNEYS: Kidneys are the major organs of urinary system. Formation of urine takes place in kidneys which are two bean shaped organs lying close to the lumbar spine, one on each side of the body.
  • URETERS: These are muscular tubes extending from the kidneys to the urinary bladder. Urine flows in these tubes from kidney to the urinary bladder.
  • URINARY BLADDER: Urinary Bladder collects urine before it is excreted from the body. Urinary bladder is a hollow muscular and elastic organ siting on the pelvic floor
  • URETHRA: Urethra is a tube that connects the urinary bladder to the external genitalia for elimination from the body.
  • SPHINCTER MUSCLES: There are two sphincter muscles to control the elimination of urine from human body. The external of the two muscles is striated and is under voluntary control of the body.

Functions of Urinary System


As stated above, urinary system is the excretory system of human body. It performs the following important functions

  1. FORMATION AND ELIMINATION OF URINE: The main function of urinary system is formation and elimination of urine. Urine is formed by the kidneys in 3 steps; 1) Glomerular Filtration, 2)Tubular reabsorption, and 3)Tubular secretion. For more details on the process of formation of urine, visit “”.
  2. OSMOREGULATION: Kidneys are important osmoregulatory organs of human body. THey maintain salt and water balance of the body. If the concentration of salt or water is increased above normal, kidney will excrete the excess amount. If the concentration is decreased, kidneys will reduce the loss of water and salts in urine.
  3. ACID BASE BALANCE: Kidneys are important regulators of pH of body fluids. Kidneys keep the pH balanced within a very small range and provide an optimum environment for all processes of life.
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Digestive System

Human Organ Systems ,
Digestive System

Digestive System Outline



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Organs
Oral 
cavity
It is the cavity of mouth, irregular in
shape, contains tongue, teeth and
salivary glands,
Esopha-
gus		Muscular tube passing the food from
pharynx to stomach
StomachMuscular, hollow and dialted part of
alimentary canal, involved in both
mechanical and chemical digestion
of food, secretes strong acid and
enzymes to aid in digestion of food
Small 
Intestine            
Lies between stomach and large
intestine, majority of digestion and
absorption takes place here,
About 5 meters in length
Large IntestineSecond-to-last part of alimentary
canal, main function is to absorb
water from indigestible food.
AnusLast part of alimentary canal, opens
to outside for ejestion of food,
Controls the expulsion of feces
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Organs
LiverProduces bile for emulsification
of fats
PancreasSecretes pancreatic juice
containing different digestive 
enzymes into the small 
intestine
TeethChewing and mastication of food
TongueRolling and lubrication of food

Functions

Digestion and absorption of food

Introduction to Digestive System


Digestive system is the food processing system of human body. The whole digestive system is in the form of a long, hollow, twisted and turned tube, called the alimentary canal, which starts from the oral cavity and ends at the anus. The overall process of digestion and absorption of food occurs in this tube. The tube is divided into different parts on the basis of structure and function of each part. These parts are described below.



Digestive System

Digestive system is the food processing system of human body. The whole digestive system is in the form of a long, hollow, twisted and turned tube, called the alimentary canal, which starts from the oral cavity and ends at the anus. The overall process of digestion and absorption of food occurs in this tube. The tube is divided into different parts on the basis of structure and function of each part. These parts are described below.

Parts of Digestive System


Human digestive system consists of the two categories of parts. The first category consists of those organs that are directly involved in the process of digestion and absorption. The second category consists of those organs that aid the process of digestion and absorption of food by producing chemical substances or by some other way, but are not directly involved in the process of digestion and absorption. The first category of organs may be called as “necessary organs” and the second category as “accessory organs” but it should be kept in mind that without the aid of accessory organs, the process of digestion is seriously impaired. When the accessory organs fail to perform their functions completely, the process of digestion may also completely stop.

Necessary Organs of the Digestive System


  1. ORAL CAVITY
  2. ESOPHAGUS
  3. STOMACH
  4. SMALL INTESTINE
  5. LARGE INTESTINE
  6. ANUS

Accessory Organs of the Digestive System


  1. LIVER AND GALL BLADDER
  2. PANCREAS
  3. SALIVARY GLANDS
  4. TEETH
  5. TONGUE

Functions of Digestive System


As stated above, digestive system is the food processing system of human body. The food taken by human beings is digested into simpler molecules that can be absorbed into the blood and utilized for various functions of human body. As the digestive system is the only route of intake of nutrients (in normal conditions), therefore necessarily all the nutrient requirements of human body are fulfilled by this system alone. If the digestive system is impaired for some reason, health of the affected individual will seriously decline.

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Endocrine System

Human Organ Systems ,
Endocrine System

Endocrine System Outline



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Typical
Endocrine
Glands
Pituitary GlandMaster galnd of the body, It has two lobes,
Present at the base of brain in form of a
protrusion, Secretes 9 different major
hormones
Thyroid GlandOne of the largest glands of body, Found
in neck below the thyroid cartilage, Mainly
controls body metabolism, Secretes 3 different hormones
Parathy-
roid
Glands		Four in number, located behind the thyroid
gland, produce parathormone
Adrenal GlandsFound attached to the kidneys, Consists of
two parts; Cortex and Medulla, Adrenal
cortex produces 3 different hormones
and adrenal medulla produces 4 
different hormones
Organs
with
Secondary
endocrine
 function

Pancre-
as		Primarily an organ of digestive
system, produces 4 different 
hormones including Insulin 
and Glucagon
Gonads Primarily organs of reproductive
system,Testes in males produse 
testosterone,Ovaries in females 
produce Estrogens and 
Progesterone
LiverPrimarily a metabolic organ of human
body, produces 3 different types of
hormones
KidneysPrimarily an organ of Excretory system,
Produces 4 different types of hormones

Functions

Generally it parallels the associates the nervous system in control of body activitie, Each hormone has a specific function,

Introduction to Endocrine System 


Endocrine system is the system of glands of human body. Each of these glands secretes one or more different hormones in the blood for different functions. The secretions of endocrine glands are known as hormones. Each endocrine gland may secrete one or more hormones in the blood and these hormones may or may not have related functions. Generally the hormones regulate different functions of human body like growth, mood, development, and metabolism etc. The perform their function by attaching to the target cells and then communicating with them.



Endocrine System


Endocrine Glands


Endocrine glands are ductless glands of human body that pour their secretions (hormones) directly into the blood. They have three characteristic features that are:
  1. They are ductless
  2. They are highly vascularized
  3. They possess intracellular vacuoles or granules that store the hormones
In contrast to the endocrine glands are the “exocrine glands”. 

Endocrine glands of Human Body


Endocrine glands of human body are divided into two categories; 1) Typical endocrine glands, 2) Organs having secondary endocrine function
1) TYPICAL ENDOCRINE GLANDS: These glands have primary function of producing hormones for human body. Typical endocrine glands include;
  1. PITUITARY GLAND
  2. THYROID GLAND
  3. PARATHYROID GLANDS
  4. ADRENAL GLANDS



Typical Endocrine Glands

2) ORGANS HAVING SECONDARY ENDOCRINE FUNCTION: These organs primarily belong to some other system of the body but have a secondary function of producing hormones. They include;
  1. PANCREAS(Hormones of Pancreas)
  2. OVARIES (In females) (Hormones of Ovaries)
  3. TESTES (In males) (Hormones of Testes)
  4. KIDNEYS (Hormones of Kidneys)
  5. LIVER (Hormones of Liver)

Functions of the Endocrine system


As stated above, endocrine system is a regulatory system of human body. In fact it associates the nervous system in controlling body functions. The control of body function by the nervous system is called nervous coordination and the control of body functions by the endocrine system is called chemical coordination. For a detailed explanation of the difference between nervous coordination and chemical coordination visit “”. The control of body functions by the endocrine system is a long term control system. All the necessary changes and adaptations of the body, required for the long term control of a specific function, are influenced by the hormonal system.

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