TISSUE

Definition: Tissue may refer to a group of biological cells that perform a similar way to function.

Histology: It is a branch of medical science which deal with the study of tissue.

Types of Tissue

1.     Epithelium Tissue:

·       (EpI-Upon Thelium-membrane)

·       This tissue grows upon a basement membrane.

·  Epithelial layers contain no blood vessels, so they must receive nourishment via diffusion of substances from the underlying connective tissue, through the basement membrane.

Classification of Epithelium Tissue:

A.    Based on number of layers:

·       Simple Epithelium: It is a single layered or one cell thick. Every cell in direct contact with the underlying basement membrane

·       Stratified Epithelium: It is multi-layered.

B.    Morphology of their cells:

·       Squamous epithelium (flat and scale like cells)

·       Cuboidal epithelium (Cube-shaped cells)

·       Columnar epithelium (Column-Shaped cells)

Epithelium tissue is present in outer layer of skin, inner lining of mouth, digestive tract, visceral organ, blood vessels and glands.

Functions of Epithelium Tissue

·       This tissue is responsible for absorption of water & nutrient, elimination of waste, secretion of enzymes, hormones and protection.

 

2.     Connective Tissue: Connective tissue that connects supports, bind or separates other tissues or organs. All connective tissue consists of three main components:

·       The cells of connective tissue include fibroblast, adipocytes, macrophages, mast cells etc.

·       The fibers: elastic, collagenous fibers.

·       The ground substances (matrix)

Types of Connective tissue:

There are three types of connective tissue:

a)     Fibrous connective tissue: e.g. Adipose tissue, Areolar tissue

·       Ligaments: the fibrous connective tissue which joint bone to bone strongest ligaments of human body is illio femoral ligament which joint hip joint (ilium) to femur in front of the joint.

·       Tendon: The fibrous connective tissue which joint bone to muscle. Strongest tendon of human body is Achilles tendon of heal cord or calcaneal tendon, situated at back of the leg, which joint the heal bone to calf muscle.

b)    Skeletal connective tissue: It include bone and cartilage

·       Osteoblast: bone forming cell.

·       Osteoclast: bone destructing or shaping cell.

·       Chondroblast: cartilage forming cell.

v The fibrous connective tissue and skeletal connective tissue provide the mechanical support to human body.

c)     Fluid connective tissue:

·       It includes blood, plasma and lymph.

·       The matrix of fluid connective tissue is in liquid state.

 

3.     Muscular Tissue: muscular tissue is soft tissue that composes muscle and gives rise to muscle ability to contract.

·       Myocyte: Muscle forming cell.

·       Myogenesis: The process of muscle formation.

Types of Muscular tissue:

There are three types of muscle in human body:

a)     Skeletal muscle: they are striated in structure and under voluntary control is situated in association with skeletal muscle are multinucleated usually. The skeletal muscles form 40 to 50% of body mass.

·       Sarcomere: it is defining as the structural and functional unit of skeletal muscle. It is also called the basic contractile unit of muscle.

·       Functions: they carry out movement of the body, maintain the posture of the body and support the body.

b)    Smooth muscle: Smooth muscle is situated in association with visceral, it is also called visceral muscle. They are Non-striated and Involuntary in nature.

·       Function: they are responsible for the contractility of hollow organs, such as blood vessels, GI Tract, bladder etc.

c)     Cardiac Muscle: They forms the musculature (myocardium) of the heart. These muscles are striated and Involuntary in nature.

·       Function: cardiac muscles are the self –contacting, automatically regulated and must continue to contract in rhythmic fashion for the whole life of the human.

4.     Nervous Tissue: Nervous tissue consists of Neurons and supporting cells.

·       Neuron or nerve cell is defined as the structural and functional unit of nervous system.

·       Neuron is similar to any other cell in the body having nucleus and all the organelles in cytoplasm, however, it is different from other cell by two ways:

                      i.          Neuron has branches or processes called Axon and Dendrites.

                    ii.          Neuron does not have centrosome, so it cannot undergo division that’s why have minimum power or regeneration.

Types of Nervous tissue:

On the basis of function, nerve cells are classified in to two types:

a)     Sensory or afferent Neurons: They carry the sensory impulses from periphery to CNS.

b)    Motor or Efferent neurons: They carry the motor impulses from CNS to periphery.

v Synapse: The junction by which the neurons communicate with each other.

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