Cells in human Body:
Human body has a number of cells and related tissues. Since the Cell is the basic unit of any tissue, it decides the type, nature and function of the tissues.
A group of different types of cells form tissues in the human body and one or more types of tissues form organs. These body organs working in mutual manner form the organ systems.
If any tissue is damaged, it actually means the cells and cell structure in the organ is damaged. These damaged cells decides the fate of entire tissue i.e. either to recover or die. Many cells have internal tendency to multiply and help in repair while few don’t have this property. Let’s see various cells of human body with their functions.
Types of cells based on tissue they form
1. Bone cells (Osteocytes) They are the toughest cells as they are bound together by calcium and phosphate material. As one knows they give strength, support and frame-work to the body by forming organs in skeletal system i.e bones.
2. Cartilage cells (chondrocytes)- These cells are similar to bone cells but the surrounding material is just loose and flexible compared to those of bone cells. Hence they are freely bendable. They are present in ear bone (hence ears are fold-able), in between large bones to help them bend and move freely like in between two ribs, spinal bones, joints etc.
3. Nerve cells: These cells are very long and have many branching at either ends. Their specialty is they never multiply in one’s life time.They are present all over the body and are sometimes as long as few meters long. They are human brain cells and are found in plenty in brain and the spinal cord and form the nervous tissue.
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4. Epithelial cell: These cells are very simple cells which form covering of other cells. These cells form covering layers of all the organs and hence are preset in skin. scalp. in the buccal cavity surface etc.
5. Muscle cells: These cells are of muscle tissue mostly long, large and have ability to contract and relax providing movements. They are three types as skeletal, cardiac and smooth muscles.
- Skeletal muscles cells are attached to long bones and assist in their movement (by muscle contraction).
- Cardiac muscles cells are present only in heart muscle and responsible for heart beats.
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- Smooth muscle cells are flexible yet, can contract and relax and are present in stomach, intestine, blood vessel walls (vascular tissue) etc. helping in movement of food through the gut.
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6 Secretory cell: These cells as name indicates are secretory in nature. They form glands and secrete something important ex; pancreatic cells which secrete insulin, glucagon, oil on the skin etc.They are found in all secretory organs.
7. Adipose cells: These are fat cells and are storage in nature to store fat. Especially seen in the soles, palms, bums etc. They reduce friction to the body.
8. Blood cells: These cells include RBC’s, WBC, Thormbocytes etc. They are always motile and never stay in one place. They have limited life span and they never multiply to form new cells. instead new cells are formed from other cells.
Types of cells in human body based on their function:
Conductive cells: Nerve cells, muscle cells come under this category. They have internal ability to conduct an electric impulse from region to other distant region in the body.
Connective cells: Bone cells, blood cells come under this category. They help connect other cells and tissues.
Glandular cells: These cells secretory cells. They form glands like pancreas,salivary glands etc and help in production of enzymes, hormones etc.
Storage cells: Adipose cells, some liver cells etc act to store materials for later use.
Supportive cells: These are the cells which are present as support to adjacent cells. Ex: Glial cells in the brain and spinal cord help provide nourishment to the nerve cells and also protect them from shocks and trauma.
Special type of cells: These are specialized cells with important functions in the body.
Sperms: These cells unlike other cells are haploid (one set of chromosome) present only in males, they have a tail which enables them to swim and move in female uterus. They have an enzyme namely hayaluronidase which helps penetrate uterine tissue and reach oocytes.
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Oocytes: Cells are haploid and present in adult female genital system before menopause.
Stem cells: These are basic cells or parent cells which can differentiate into any cell based on the requirement. These stem cells in human body are given so importance due to their promising role in treatment of disorders in future. See the article on stem cell storage.
Rods & cones: These cells are in eye and have capacity to capture image colour and light.
Ciliated cells: These cells are present as lining of respiratory tract, esophagus etc. and have a pointed thread like cilia which move in one particular direction to pass material.
Human tissue types are again dependent on the types of cells involved in their formation.