[ جميع الكليات ] : Body Systems

[Dr ʀeнαв]

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What is a human body system?

A system of human body means a collective functional unit made by several organs in which the organs work in complete coordination with one another. Organs cannot work alone because their are certain needs of every organ that need to be fulfilled and the organ itself cannot fulfill those needs. So all organs of human body need the support of other organs to perform their functions and in this way an organ system is formed.

Example of dependance of organs of a system on one another:

Organs of a system are dependant on one another

Systems of the Human Body:

Human body is made of ten different systems. All the systems require support and coordination of other systems to form a living and healthy human body. If any one of these systems is damaged, human body will become unstable and this lack of stability will ultimately lead to death. The instability caused by damage of one system cannot be stabilized by other systems because functions of one system cannot be performed by other systems. Knowledge of human body systems is very important for a medical professional because it is the base of all medical sciences and clinical practices. Although, generally, the structural aspects of human body systems are studied in anatomy and the functional aspects are studied in physiology but it is very important to have a coordination between the two subjects because knowledge of structure is incomplete without the knowledge of function and the knowledge of function is incomplete without the knowledge of structure.

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[Dr ʀeнαв]

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Introduction to Human Skeletal System:

Skeletal system is the system of bones, associated cartilages and joints of human body. Together these structures form the human skeleton. Skeleton can be defined as the hard framework of human body around which the entire body is built. Almost all the hard parts of human body are components of human skeletal system. Joints are very important because they make the hard and rigid skeleton allow different types of movements at different locations. If the skeleton were without joints, no movement would have taken place

and the significance of human body; no more than a stone.

Components of Human Skeleton:

Human skeleton is composed of three main components; Bones, Associated cartilages and Joints.

Bones:

Bone is a tough and rigid form of connective tissue. It is the weight bearing organ of human body and it is responsible for almost all strength of human skeleton. “.

Cartilages:

Cartilage is also a form of connective tissue but is not as tough and rigid as bone. The main difference in the cartilage and bone is the mineralization factor. Bones are highly mineralized with calcium salts while cartilages are not

Joints:

Joints are important components of human skeleton because they make the human skeleton mobile. A joint occurs between “two or more bones”, “bone and cartilage” and “cartilage and cartilage”.

Divisions of Human Skeleton:

Human skeleton can be divided into two divisions.

Axial Skeleton:

Axial skeleton forms the axis of human body. It consists of Skull, vertebral column and thoracic cage.

Skull: Skull is that part of human skeleton that forms the bony framework of the head. It consists of 22 different bones that are divided into two groups: bones of cranium and bones of face.

Vertebral Column: It is a flexible column of vertebrae, connecting the trunk of human body to the skull and appendages. It is composed of 33 vertebrae which are divided into 5 regions: Cervical, Thoracic, Lumbar, Sacral, and Coccygeal.

Rib Cage: It is a bony cage enclosing vital human organs formed by the sternum and ribs. There are 12 pairs

of ribs that are divided into three groups: True ribs, False ribs, and Floating ribs.:.

Axial Skeleton

Appendicular Skeleton:

It is the skeleton of appendages of human body. It consists of Shoulder girdle, Skeleton of upper limb, Pelvic girdle and Skeleton of lower limb.

Shoulder Girdle:

It attaches the upper limb to body trunk and is formed by two bones: clavicle and scapula.Clavicle is a modified long bone and is subcutaneous throughout its position. It is also known as the beauty bone. For more details on clavicle, visit:”"Scapula is a pear shaped flat bone that contains the glenoid fossa for the formation of shoulder joint. It possesses three important processes: Spine of scapula, Acromion process and Coracoid process.“”.

Skeleton of Upper limb:

The skeleton of each upper limb consists of 30 bones. These bones are: Humerus, Ulna, Radius, Carpals (8), Metacarpals (5), Phalanges (14(.

Pelvic Girdle:

There are two pelvic girdles (one for each lower limb) but unlike the pectoral girdles, they are jointed with each other at symphysis pubis. Each pelvic girdle is a single bone in adults and is made up of three components: Ileum, Ischium and Pubis.“.

Skeleton of Lower limb:

The skeleton of each lower limb consists of 30 bones. These bones are; Femur, Tibia, Patella, Tarsals (7), Metatarsals (5), Phalanges (14.

Functions of human skeleton:

Human skeleton performs some important functions that are necessary for survival of human beings.

STRENGTH, SUPPORT AND SHAPE: It gives strength, support and shape to the body. Without a hard and rigid skeletal system, human body cannot stand upright, and it will become just a bag of soft tissues without any proper shape

PROTECTION OF DELICATE ORGANS: In areas like the rib cage and skull, the skeleton protects inner soft but vital organs like heart and brain from external shocks. Any damage to these organs can prove fatal, therefore protective function of skeleton is very important

LEVERAGE FOR MOVEMENTS: Bones of the human skeleton in all parts of body provide attachment to the muscles. These muscles provide motor power for producing movements of body parts. In these movements the parts of skeleton acts like levers of different types thus producing movements according to the needs of the human body.

PRODUCTION OF RED BLOOD CELLS: Bones like the sternum, and heads of tibia have hemopoeitic activity

(blood cells production). These are the sites of production of new blood cells.

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[Dr ʀeнαв]

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Introduction to Muscular System:

Muscular system is the system of Human Body that provides motor power for all movements of body parts. Muscular system is composed of special tissue called muscular tissue. Muscles have the ability to contract actvely to provide the force for movements of body parts. Muscular system is an important system of human body because without it, life will completely stop. Muscles produce not only those movements that are under the control of our will and that we can see and feel, but also those movements that are responsible for activities like breathing, digestion of food, pumping of blood etc.

Muscles:

Muscles are body tissues that provide the force for all body movements. They are made of special types of cells“”.

Types of muscles:

Muscles are basically of three types; Skeletal Muscles, Smooth Muscles and Cardiac Muscles.
Skeletal Muscles:
Skeletal muscles form most of the human body weight. They are under the control of human will and all body movements occurring by our will are produced by skeletal muscles. They are called skeletal muscles because they are almost always found attached to the skeleton and produce movements in different parts of the skeleton.
Smooth Muscles:
Smooth muscles form the soft body organs like stomach, intestine, blood vessels etc. They are not under the will of human beings and are responsible for unconscious body activities like digestion of food. They are called smooth muscles because when seen under the microscope, they do not have any striation in contrast to the other two types of muscles.
Cardiac Muscles:
Cardiac muscles are exclusively found in human heart and no where else. They are extremely strong and powerful muscles. They are not under the control of human will and are involuntary. The pumping of blood by human heart is because of the force provided by the contraction of cardiac muscles.

Skeletal Muscle

Smooth Muscle

Cardiac Muscle

Functions of Muscular System:

Muscular system has the following important functions in human body;

MOVEMENTS OF BODY PARTS: Skeletal muscles are responsible for all voluntary movements of human body parts. They provide the force by contracting actively at the expense of energy. In other words, muscles are motors of body where chemical energy of food is converted into mechanical work.

STABILITY AND POSTURE: Skeletal muscles stabilize human skeleton and give a proper posture to human beings. Some joints of human body are weak and they require the support of muscular system to achieve stability. Skeletal muscles are very important for such joints.

HEAT PRODUCTION: A large share of body’s energy is used by muscular system. As a result of high metabolic rate, muscles produce great amount of heat in the body. Heat produced by muscles is very important in cold climates.

CIRCULATION: Cardiac muscles provide the main force for circulation of blood throughout human body. The regular pumping of heat keeps the blood in motion and nutrients are readily available to every tissue of human body.

HELP IN DIGESTION: Smooth muscles of organs like stomach and intestine help the digestive system in the

process of digestion of food

.

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[Dr ʀeнαв]

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Introduction to Nervous System:

Nervous system is the chief controlling and coordinating system of the body. It controls and regulates all voluntary and involuntary activities of human body. There are three characteristic properties of nervous system of human body; Sensitivity,Conductivity and Responsiveness

Neuron is the unit of nervous system:

The structural and functional unit of nervous system is called neuron. It is a special type of cell with a cell body and cell processes. For more details about the structure of neuron, see the basic anatomy article”".

Parts of nervous system:

Nervous system of human body is divided broadly into two parts; Central Nervous System (CNS) and Peripheral Nervous System (PNS)
CENTRAL NERVOUS SYSTEM (CNS) : Central nervous system includes brain and spinal cord.
PERIPHERAL NERVOUS SYSTEM (PNS) : Peripheral nervous system includes all the parts of nervous system except brain and spinal cord. It is further divided into two components; Somatic nervous system and Autonomic nervous system.

Nerves:

Nerves are solid cords composed of bundles of nerve fibers (each nerve fiber is an axon with its coverings) bound together by connective tissue. Nerves are of two types; Spinal nerves and Cranial Nerves.
Spinal Nerves: Spinal nerves arise from the spinal cord. There are 31 pairs of spinal nerves in human body. For more details on spinal nerves, see the basic anatomy article “”.
Cranial Nerves Cranial nerves arise from the brain. There are 12 pairs of cranial nerves in human body “”.

Functions of nervous system:

CONTROL OF ALL BODY FUNCTIONS: Nervous system is the master system of human body. It controls the activity of all other systems in such a way that all the systems collectively make a human being. Without a controlling system, there is no concept of life because in such case there will be no coordination between different body functions and they will all act separately. Nervous system not only controls the voluntary functions of human body that are directed by human will, but it also controls those functions that are below the level of consciousness of human beings. Control of a function means that the intensity of that function can be increase or decreased according to the demands of human body.

COORDINATION OF DIFFERENT BODY ORGANS: Nervous system not only produces coordination between different systems, but also between different organs of a system. To form an organ system, role of the component organs must also be coordinated. So nervous system is not only important for formation of an organism by different organ

systems, but also for formation of a system by different organs of human body.

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[Dr ʀeнαв]

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Introduction to Respiratory System:

Respiratory system is the system of respiratory passages, lungs and respiratory muscles of human body. Respiratory system is responsible for exchange of gases between the human body and the surroundings. In the process of exchange of gases, human body gains oxygen and gets rid of carbon dioxide. Other gases of the atmosphere have no significant role in human respiratory system. Respiratory system is extremely important for human body because the process of respiration cannot be stropped even for a few seconds. If the process of respiration stops even for a minute or two, the condition will become serious and will ultimately end in death.

Organs of human respiratory system:

The main organs of human respiratory system are lungs and respiratory passages. Muscles of respiration also form a component of respiratory system but there importance is rather little as compared to lungs and respiratory passages.
Lungs:
Lungs are the organs of human body where gaseous exchange take place. Human beings have two lungs known as the right and left lungs. Lungs are soft, spongy and very elastic

Respiratory Passages:
Respiratory passages or air-ways are the conducting portions of human respiratory system. Here no exchange of gases take place, but they guide the air to go to the lungs and not anywhere else in the body. Conducting portion of the human respiratory system consists of; Traches, Bronchi, Bronchioles, Alveolar sacs and Alveoli.

Lungs and Conductive passages

Functions of Respiratory System:

GASEOUS EXCHANGE: Main function of respiratory system is gaseous exchange. Through respiratory system new air is always brought into the body and used air is expelled out. In this way oxygen is gained and carbon dioxide is lost by the body.

EXCRETION OF CARBON DIOXIDE: Respiratory system is the major system for excretion of carbon dioxide from the body. Carbon dioxide is produced as a result of metabolic break down of carbohydrates in body and must be eliminated quickly. Carbon dioxide is brought to the lungs by blood and is lost from the lungs through gaseous exchange with fresh air in lungs.

OXYGENATION OF BLOOD: Oxygen is required by the body for break down of food and must be continuously supplied for continuous supply of energy. Supply of oxygen is maintained by respiratory system.

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Introduction to Cardiovascular System:

Cardiovascular System

Cardiovascular system means the system of heart and blood vessels of human body. The term “cardiovascular” is a combination of two word; “Cardio” and “vascular”. The term “cardio” is derived from “cardiac” meaning Heart and the term “vascular” means blood vessels. So the name itself indicates that cardiovascular systems is the system of heart and blood vessels. Cardiovascular system is also known as “Circulatory System”.
Components Of Cardiovascular System:

Cardiovascular system is made up of three major components; Heart, Blood vessels and blood.
HEART:Heart is a hollow muscular organ made of strong cardiac muscles. Heart can push the blood through the circulatory system with great force. In fact push of the heart is the major force that causes circulation of blood throughout human body. Heart is made up of three layers; Pericardium, Myocardium and Endocardium.

Human Heart

BLOOD VESSELS:Human beings have a closed type of circulatory system (visit my blog post: Difference between open and closed circulatory systems) in which blood does not come in direct contact with body tissues. Instead the blood flows in restricted pathways called blood vessels. Materials are exchanged between blood and body tissues through the walls of blood vessels. Thus blood vessels are pathways of blood flow in human body. There are three main types of blood vessels; Arteries, Capillaries and Veins
BLOOD: Blood is a specialized tissue of body that exists in fluid form. It is one of the five basic types of tissues of human body. (Blog post:Basic tissue types of Human Body). Blood consists of two major portions: Blood cells and Plasma. Plasma is the watery portion of blood that makes it a fluid. 90% of blood plasma is water and remaining 10% are proteins, inclusions and waste products etc. Blood cells are of three main types: Red Blood Cells (RBCs), White Blood Cells (WBCs) and Platelets. :”".

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Introduction to Lymphatic System:

Lymphatic system is the drainage system of human body and is accessory to the venous system. At arterial ends of capillaries fluid leaks out and at the venous end, it is absorbed back in. Some of the fluid remains in the tissue spaces. This fluid is called lymph and the system by which this lymph is returned back to blood is called lymphatic system. In addition to its drainage function, lymphatic system is also an effective defense system of the body because some organs of the lymphatic system (lympho-reticular organs) are involved in defense activities of the body.

Components of lymphatic system:

Lymphatic system is composed of the following important components.
LYMPH VESSELS:Lymph vessels are pathways for flow of lymph around the body. Lymph vessels begin as lymph capillaries that begin blindly in tissue spaces and lead to larger lymph vessels. Lymph vessels do not arise from avascular structures, brain, spinal cord, bone marrow and splenic pulp. Larger lymph vessels anastomose freely with one another and they ultimately drain the lymph into the venous system.
CENTRAL LYMPHOID TISSUE: Central lymphoid tissue consists of bone marrow and thymus.
PERIPHERAL LYMPHOID ORGANS: Peripheral lymphoid organs are lymph nodes, spleen and epithelio-lymphoid tissues (lymphoid tissue present in epithelium e.g. lymphoid tissue of alimentary and respiratory tracts).
CIRCULATING POOL OF LYMPHOCYTES: It contains mature progenies of T-lymphocytes and B-lymphocytes. They form the first line of defense of the body during antigenic emergencies.
Functions of Lymphatic System:

REMOVE PARTICULATE MATTER: Lymph capillaries absorb and remove large protein molecules and other particulate matter from tissue spaces. In this way cellular debris and other harmful particles are washed away.

FILTER THE LYMPH FOR FOREIGN HARMFUL PARTICLES: Lymph nodes act as filter for the lymph and in this way they purify the lymph flowing through them.

PHAGOCYTOSIS: Antigens are removed from lymph by phagocytic activity of cells of lymph node.

PRODUCTION OF LYMPHOCYTES: Mature B-lymphocytes and mature T-lymphocytes are produced in lymph nodes.

IMMUNE RESPONSES: Lymphatic system can induce both cellular and humoral

immune responses.

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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 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:

They are ductless

They are highly vascularized

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;

PITUITARY GLAND

THYROID GLAND

PARATHYROID GLANDS

ADRENAL 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;

PANCREAS(Hormones of Pancreas)

OVARIES (In females) (Hormones of Ovaries)

TESTES (In males) (Hormones of Testes)

KIDNEYS (Hormones of Kidneys)

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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[Dr ʀeнαв]

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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.

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:

• ORAL CAVITY
• ESOPHAGUS
• STOMACH
• SMALL INTESTINE
• LARGE INTESTINE
• ANUS

Accessory Organs of the digestive system:

• LIVER AND GALL BLADDER
• PANCREAS
• SALIVARY GLANDS
• TEETH
• 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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[Dr ʀeнαв]

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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.

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;

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.

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.

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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