Term Paper on the Types of Tissue | Cells | Biology

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Term Paper on Types of Tissue


Term Paper # 1. Epithelial Tissue:

Forms epithelium lines the body cavities, tubes and covers the outer surface of the body.  

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It is classified as shape of cells, number of cells, layers and cell surface modifications.

I. Simple Epithelium:

The following are the three types of epithelium, variety of Simple Epithelium – I.

(i) Simple Squamous Epithelium:

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a. It is meant for exchange of substances,

b. They are found in- blood vessels, alveoli, peritoneum, pleura, single layer of flat cells lying on the basement membrane.

(ii) Simple Cuboidal Epithelium:

a. It is cuboidal in shape,

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b. It is found in ducts,

For example- thyroid, ducts of G.I.T., salivary glands, single layer of cells.

(iii) Simple Columnar Epithelium:

a. It is found on secretary and absorptive surface.

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b. Cells are shaped like column, single layer of cell, height being more than width.

For example- uterus, uterine tubes, tympanic cavity, G.I.T., gall bladder, ependymal of spinal cord.

II. Pseudostratified Epithelium:

a. Cells are of different heights,

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b. They are found in respiratory tract and male genital system,

c. It is single layered and tall columnar,

d. Level of nucleus is different in different cell,

e. It gives a false appearance of stratification.

For example- trachea, bronchi, ductus deferens, male urethra etc. 

III. Stratified Epithelium:

(i) Stratified Squamous Epithelium:

a. More than one layer of cells are present – 5-6 layers,

b. Basal cells are columnar cells.

c. 2-3 layers of polygonal cells lie over it,

d. Superficial cells are flat squamous, protective in nature.

e. They are found at oral cavity, pharynx, tongue, tonsil, oesophagus, conjunctiva and cornea etc.

(ii) Keratinized Stratified Squamous Epithelium:

a. Characterised by layer of keratin over superficial cells,

b. Found at skin, it protects the exposed parts of body.

(iii) Stratified Cuboidal Epithelium:

a. Two layers of cuboidal cells,

b. It is found in large ducts, e.g., ducts of sweat glands and mammary gland, ovarian follicles etc.

(iv) Transitional Epithelium:

a. Transition of cells from basal to super­ficial layer – 5-6 layers.

b. Basal cells – columnar cells become polygonal above.

c. Superficial cells are umbrella shape,

d. It is found in urinary tract, renal pelvis, ureter, bladder, urethra etc.

(v) Stratified Columnar Epithelium:

a. Two layers of columnar cells,

b. It is found at Conjunctival fornix, anal mucous membrane etc.


Term Paper # 2. Connective Tissue:

It connects different tissues and facilitates passage of nerves and vascular bundles in different tissues,

Connective tissues are made up of cells, fibres and matrix, which are described below:

(I) Cells:

i. Resident Cells:

A. Fibroblast:

a. Large spindle shaped cells with irregular process, 

b. They produce collagen and elastic fibres.

B. Fibrocyte:

Fibrocyte is mature fibroblasts they are spindle shaped with centrally placed nucleus.

C. Adipocytes:

a. Nucleus is at peripherally place, cytoplasm contains lipids.

b. In obese state – fat cells get enlarged.

D. Mesenchymal Stem Cell:

a. Derived from mesenchyme are capable to differentiate into mature cells of connective tissue during growth and development,

b. They are pluripotent cells and have multiple processes.

c. They are phagocytose foreign bodies.

ii. Migrant Cells:

A. Macrophages

B. Plasma cells

C. Mast cells

D. Pigment cells

E. Lymphocytes

F. Monocytes.

A. Plasma Cells:

It produce antibodies, characteristic cart wheel appearance of nucleus.

B. Mast Cells:

a. It produce heparin and histamine

b. It is present around blood vessels and contain granules.

(II) Fibres:

Fibres are present in matrix of connective tissue.

They are of three types:

(i) Collagen Fibres:

a. Thick bundle of colourless fibres,

b. They branched and rebranched and take part information of framework of certain organs and glands etc..

c. It is made-up of collagen protein,

d. It is secreted by fibroblasts, chondroblasts, osteocytes and chondrocytes.

For example- lymphnodes, spleen, thymus etc..

(ii) Elastic Fibres:

a. It runs as single fibres,

b. They branch and anastomose with each other,

c. Broken ends of these fibres are recoil,

d. They are produced by fibroblasts.

(iii) Reticular Fibres:

a. They are fine collagen fibres, which form a framework for various tissues.

(III) Matrix:

Matrix or ground substance made-up of carbohydrate and protein, mucopolysaccharides and adhesive glycopro­teins are present in the matrix.

Classification of Connective Tissue:

They are classified as:

(i) Irregular Connective Tissue:

a. Loose areolar connective tissue, thin collagen and elastin fibres.

b. Dense irregular connective tissue.

c. Adipose tissue found in breast, mesentery, bone marrow etc. which contains fat cells.

(ii) Regular Connective Tissue:

a. Fibres are regularly oriented.

b. Collagen fibres are present in bundles and run in one direction, also known as white fibrous tissue,

c. It is present in tendons, ligaments and aponeurosis.

Fascia:

Collagen fibres interlace in various directions, e.g., deep fascia, aponeurosis, fibrous pericardium.

Specialized Form of Connective Tissue:

At certain places it forms a framework for the organs e.g., lymph nodes, spleen, liver, bones and cartilages. According to the need of the body stem cells of the connective tissue changes its form and takes part in the formation of blood cells, muscular and nervous tissue.

Example- Cartilage, bone, blood, muscular and nervous tissue.

Functions of Connective Tissue:

i. Binds together various structures.

ii. Facilitates passage of neuro vascular bundle.

iii. In the form of deep fascia – it keeps the tendons and muscles in position, gives origin to muscles and forms different compartments of muscles.

v. In the form of ligaments – it binds the bones.

v. Attaches muscles to bone with the help of tendons.

vi. Facilitates venous return in lower limb with the help of deep fascia.

vii. Helps in wound repair – due to presence of fibroblasts.

viii. Apponeurosis is a regular dense connective tissue.


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