HUMAN BODY ORGANS AND SYSTEMS

ORGANS

Several kinds of tissues combine together to form an ORGAN. For instance, stomach is an organ that is composed of nerve tissue, muscle tissue, and glandular epithelial tissue. VISCERA (singular: viscus) are internal organs. Abdominal viscera are the liver, stomach, large and small intestines, pancreas, spleen, and gallbladder.

SYSTEMS:

Groups of organs combine together to form a SYSTEM. Each system performs complex functions. For instance, respiratory system consists of NOSE, PHARYNX, LARYNX (VOICE BOX), TRACHEA (WINDPIPE), BRONCHIAL TUBES, AND LUNGS.

Now we can see each system and its organs:

1. DIGESTIVE SYSTEM: This system contains mouth, pharynx (throat), esophagus, stomach, intestines (small and large intestines), liver, gallbladder, and pancreas.

2. URINARY AND EXCRETORY SYSTEM: This systems consists of kidneys, ureters (from these tubes urine comes out of the kidneys to urinary bladder), urinary bladder, urethra (from this opening urine comes out of the body from urinary bladder).

3. RESPIRATORY SYSTEM: This system consists of nose, pharynx, larynx (voice box), trachea (windpipe), bronchial tubes, and lungs.

4. REPRODUCTIVE SYSTEM: This system consists of:
FEMALE: Ovaries, uterine or fallopian tubes, uterus or womb, vagina, mammary glands.
MALE: Testes and its associated tube, urethra, penis, and prostate gland.

5. ENDOCRINE SYSTEM: This system consists of thyroid gland in the neck, pituitary gland at the base of the brain, sex glands of ovaries and testes, adrenal glands above the kidneys, pancreas or islets of Langerhans, parathyroid glands, and thymus gland.

6. NERVOUS SYSTEM: This system consists of brain, spinal cord, nerves, and collections of nerves.

7. CIRCULATORY SYSTEM: This system consists of heart, blood vessels (arteries, veins, and capillaries), lymphatic vessels and lymph nodes, spleen, and thymus gland.

8. MUSCULAR SYSTEM: This system consists of muscles.

9. SKELETAL SYSTEM: This system consists of bones and joints.

10. INTEGUMENTARY (SKIN AND SENSORY) SYSTEM: This system consists of skin, hair, nails, sweat glands and sebaceous (oil) glands, eyes, ears, nose, and tongue.


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TISSUES - ITS TYPES AND ITS FUNCTIONS

To do a specialized activity, same cells combine together to form a tissue. Study of tissues is called Histology, and one who specialized in Histology is called Histologist.

There are different kinds of tissues in our body to perform different functions. Similar cells combine together to form a tissue.

Different kinds of tissues:

1. Nerve tissue
2. Connective tissue
3. Muscle tissue
4. Epithelial tissue

Now we study about all tissue types one by one:

1. Nerve tissue: Nerve tissues are combination of nerve cells as we have already studied the main function of nerve cells is conduction of impulses through out the body, and so the job of nerve tissue is also the conduction of impulses.

2. Connective tissue: The examples for Connective tissues are Adipose tissue, Cartilage and bone. Cartilage is an elastic and fibrous tissue attached to bones.

3. Muscle tissue: There are two types of Muscle tissues in our body such as Voluntary muscles and Involuntary muscles. Voluntary muscles are found in legs and arms and in the parts of the body where the movement is voluntary. Involuntary muscles are found in our body where the movement is involuntary or the movement is not in our conscious control, such as heart and digestive system. Cardiac muscle is a best example for an involuntary muscle tissue.

4. Epithelial tissue: These tissues are placed through out the body as a covering or lining or internal organs in exocrine and endocrine glands as well as an external covering covers the body as skin.

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CELL AND ITS FUNCTION

The fundamental unit of every animal or plant is cells. Combination of cells is called TISSUES. Every ORGAN in the body is made up of combination of many tissues.
SAMENESS OF THE CELLS: All cells are same and they contain a gelatinous substance made up of or composed of water, protein, acids, fats, and various minerals. See the figure-1 and 2, to know the cell and its structures photographically. Now we see each and every part of the cell one by one.

1. CELL MEMBRANE: Cell membrane protects the cell and surrounds it that passes into and out of the cell.

2. NUCLEUS: The nucleus controls the structure of the cell. Cell reproduction process is directed by the nucleus only and which determines the function of the cell and the structure of the cell.

3. CHROMOSOMES: These are rod-like structures inside the cell. Human body cells (other than sex cells, the egg, and sperm cells) contain 23 pairs of chromosomes. Sex cells, such as sperm and egg cells have 23 single chromosomes only. When one egg cell unites with a sperm cell to for an embryo, then the embryonic cell has 46 chromosomes i.e. 23 pairs...understand the difference...Chromosomes contains the regions called GENES. Thousands of genes are in an orderly sequence on each chromosome. Gene is made up of a chemical substance called DNA (deoxyribonucleic acid). DNA is an important compound that regulates the activities of the cell in a sequential order on each chromosome. The DNA is a series of codes. When DNA activity carries out of the nucleus to other parts of the cell, the activities of the cell i.e. cellular reproduction and the manufacture of proteins are controlled by DNA.

Chromosomes in the nucleus can be analyzed to look at their arrangement, size, and number by doing a KARYOTYPE. Karyotyping of chromosomes is important in determining whether chromosomes are normal in number and structure. Karyotyping will be done by doctors by puncturing the sac around the fetus when one woman is pregnant through amniocentesis. Abnormal numbers of chromosomes may cause some serious conditions like Down syndrome (mongolism) and trisomy-21 syndrome.

4. CYTOPLASM: It means cyto means cell, plasm means formation. Cytoplasm carries the work of a cell i.e. nerve cell conducts stimulation, muscle cell contracts. Cytoplasm contains MITOCHODRIA and ENDOPLASMIC RETICULUM.

5. MITOCHONDRIA: It is called power center of the cell. This is small and sausage-shaped bodies produce energy by burning food in the presence of oxygen. This process is called catabolism (cata-down, bol-to cast, -ism-process). This process makes complex food particles into simpler substances and energy is released after this action to do the work of the cell.

6. ENDOPLASMIC RETICULUM: These like canal-like structures-this is a network within the cell. These canals contain a very small structures called RIBOSOMES like a tunnel system in this proteins are produced for the use of the cell. This process is called ANABOLISM (ana-up, bol-to cast, -ism-process). After this process, complex proteins are made up from the simpler parts of food. Smaller proteins linked like a chain to become complex proteins in this process. Both these catabolism and anabolism in combination is called METABOLISM (meta-change, bol-to cast, -ism- process) i.e total chemical activities that occurring in a cell. In this process, the sugars and fat in the food are used up and burned quickly and so the ENERGY is released.

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