Epithelial and Connective Tissues PDF

- The human body is composed of four basic types of tissue: epithelial, connective, muscular and nervous. Characteristics of epithelial tissue: Epithelial cells are firmly bound to the underlying connective tissue by basal lamina or basement membrane. Epithelium is derived from all three embryoni...

- The human body is composed of four basic types of tissue: epithelial, connective, muscular and nervous. Characteristics of epithelial tissue: Epithelial cells are firmly bound to the underlying connective tissue by basal lamina or basement membrane. Epithelium is derived from all three embryonic germ layers: Ectodermal, endoderm and mesoderm. Functions of epithelial tissue are: 1- Protection (covering and lining of surfaces e.g. skin). 2- Absorption e.g. small intestine and kidney tubules. 3- Secretion e.g. glands. 4- Sensation e.g. neuroepithelium 5- Contractility e.g. myoepithelial cells Types of Epithelium - Epithelium is classified according to its structure and function into two main groups: 1  1. Covering and lining (surface) epithelium 2. Glandular epithelium 3. Neuroepithelium 4. Myoepithelium I - Covering and lining epithelium - They are classified according to the number of cell layers into: A- Simple epithelium that consists of one layer of cells. B- Stratified epithelium that consists of more than one layer. Simple epithelium - It is classified according to the cell shape into: 1. Simple squamous epithelium: 2 It is made of one layer of flattened plate-like cells with flattened nuclei. Sites: Lungs (lining of alveoli). Endothelium of blood vessels and heart 2. Simple cuboidal epithelium: It is composed of a single layer of cuboidal cells with round central nuclei. Sites: Thyroid follicle 3. Simple columnar epithelium: It is made of a single layer of tall cells with oval basal nuclei. It is subdivided into non-ciliated and ciliated types: a) Simple columnar ciliated epithelium: - The cells have cilia on the free surface. Sites: Bronchioles of lungs b) Simple columnar non-ciliated epithelium: Sites: The gastro intestinal tract (from the stomach to the rectum). 4. Pseudostratified columnar epithelium: - All the cells are attached to the basal lamina but some of them do not reach the surface. - The nuclei appear to lie in various layers and result in the false appearance of stratified epithelium. - This type may be ciliated or non-ciliated. a) Pseudostratified columnar ciliated epithelium - This type is usually associated with goblet cells. Sites: Respiratory passages e.g.: 3 Most of nasal cavity Larynx Trachea Bronchi b) Pseudostratified columnar non-ciliated epithelium Sites: Large ducts B- Stratified Epithelium - The epithelium is made up of layers of cells. - It is classified according to the shape of the most superficial layer of cells into squamous, cuboidal, columnar and transitional epithelium. 1. Stratified squamous epithelium: - The most superficial layers are squamous or flattened a) Stratified squamous non keratinized epithelium Sites: 4 Mouth cavity Vagina. b- Stratified Squamous keratinized epithelium Sites: Epidermis of skin. 2. Stratified cuboidal epithelium The most superficial cells are cuboidal in shape. Site: Lining ducts of sweat glands. 3. Stratified columnar epithelium: The superficial cells are columnar. a) Stratified columnar non ciliated epithelium Sites: conjunctiva b- Stratified columnar ciliated epithelium Sites: Fetal esophagus 4. Transitional epithelium This epithelium lines the urinary passages. In the empty or relaxed condition, the epithelium is made of 3-8 layers. The superficial layer is composed of dome shaped cells with 1-2 nuclei. When the organs are distended, the epithelium becomes stretched the superficial layers become squamous. Sites: urinary passages: pelvis of the kidney, ureter, urinary bladder. II- Glandular epithelium - They are formed of cells specialized to produce a secretion. 1- The endocrine glands: They are ductless glands and secrete directly into blood stream. 5 2- The exocrine glands: They have ducts through which the secretions pass to the surface. 3- Mixed exocrine and endocrine glands: e.g. in liver and pancreas. According to the nature of secretion 1- Mucous glands: - Mucous cells are characterized by: a) Pale cytoplasm (mucous is not stained by Hx.& E.). b) Basal flattened nucleus. 2- Serous glands which secrete a watery secretion. - Serous cells are characterized by: By LM: a- Basal basophilia. b- Apical acidophilic secretory granules. c- Central rounded nucleus. 3- Mixed glands which secrete both mucous and serous secretions. Mixed acini are mucous acini with a deimlune of serous cells. According to the branching of the ducts and secretory portion into: 6 1- Simple glands that have only one unbranched duct and one secretory unit. 2- Simple branched glands which have one duct and branched secretory units. 3- Compound glands which have branched ducts and branched secretory units. IV- According to the shape of the secretory portion into: 1- Tubular. 2- Alveolar (acinar). 3- Tubuloalveolar units. 7 Functions: 1. Supportive 2. Defensive 3. Nutritive Structure: I- Intercellular substance: 1) Ground substance. Structure: A- Glycosaminoglycans. B- Glycoproteins 2) Fibers. II- C.T. Cells 8  GIycosaminoglycans Non sulphated Types: Sulphated Hyaluronic acid : Dermatan sulphate: : Chondroitin sulphate: Heparan sulphate: keratan sulphate: CONNECTIVE TISSUE FIBERS Types: 1- Collagen fibers. 2- Reticular fibers. 3- Elastic fibers. 1) Collagen fibers Characters: - Fibers are wavy bundles. 9 - They are the most numerous fibers in C.T. - They are inelastic. - When aggregate they appear white as in tendon. - The collagen rich tissue is called white collagenous connective tissue. - Staining: - Pink (acidophilic) with eosin. - Blue with Mallory. - Green with Masson. 2) Elastic fibers Characters: Thinner than collagen fibers. They are elastic. Single fiber branches. Straight but recoil at their cut. When they are dense they give the tissue yellow color. The tissue rich in elastic fibers is called yellow elastic connective tissue. Structure: It is composed of: - Oxytalan.. 10 - Elastin. Staining: Brown with orcein 3) Reticular fibers - They are very thin in diameter. - Arranged in the form of network. Sites: In the stroma of different organs. Staining: - Black with silver. CONNECTIVE TISSUE CELLS 1) FIBROBLASTS AND FIBROCYTES - The most common cells in C.T. - There are two different morphologic types: a- The active stage is called fibroblast. b- The inactive (resting) stage is called fibrocyte. Fibroblast: Origin: undifferentiated mesenchymal cells (U.M.C). Shape: irregularly branched cells. 11 Nucleus: - Large ovoid - Pale staining with extended chromatin - Prominent nucleolus Cytoplasm: - Abundant basophilic. E/M - Rich in RER -Well developed Golgi. Function: - Synthesis of collagen, reticular and elastic fibers. - Synthesis of glycosaminoglycans and glycoproteins of the matrix. 2) Macrophage 12 Origin: From monocytes. - Shape: Irregular surface with protrusions and indentations. Nucleus: - Eccentric. - Kidney shaped. Cytoplasm: - Many lysosomes. - Staining: By injection of vital dyes (trypan blue or Indian ink). Functions: Defensive through Phagocytosis and digestion of foreign particles by lysosomes. Repair by removal of the necrotic tissue. 3) Mast cell Origin: From stem cells (U.M.C). Cytoplasm: filled with metachromatically stained granules. Staining: Metachromatically with toluidine blue. Function.The granules contain: Heparin which is anticoagulant Histamine in hypersensitivity Eosinophil chemotactic factor 13  4) Plasma cell Origin: B-lymphocyte. Nucleus: - Eccentric. - With condensed chromatin in the form of cart wheel or clock-face appearance. Function: Synthesis of antibodies Types of connective tissue A- C.T. Proper: Loose. Dense: Regular and Irregular. B- C.T with special properties: Adipose Elastic Mucous 14 Reticular Haematopoietic C- Supporting C.T: 1. Cartilage 2. Bone Connective tissue proper - There are two classes: 1. Loose (aeriolar) most widespread. 2. Dense a) Regular as in tendon. b) Irregular as in capsules of organs Mucoid C.T. - It has abundant jelly like - Sites: Umbilical cord (Wharton's jelly). Adipose connective tissue It is a special type of connective tissue in which adipocytes predominate. Types of adipose C.T.: 1- Unilocular (yellow) adipose tissue. 2- Multilocular (brown) adipose tissue. Staining of fat: Dissolve in during Hx. E. staining and appear as vacuoles. Orange by Sudan III. Black by osmic acid. 15 16