EPITHELIUM 3/12/2018 د. درويش بدران د. ماهر الحديدي د.امجد الشطرات و احسان العمري

Transcription

1 EPITHELIUM 1

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4 1- SIMPLE SQUAMOUS EPITHELIUM It is a single layer of flat cells that resembles a tiled floor when viewed from apical surface; centrally located nucleus that is flattened and oval or spherical in shape. 4

5 Most common locations of the simple squamous epithelium A) Forms the epithelial layer of serous membranes a- PERITONEUM b-pleura c-pericardium where it is called Mesothelium 5

6 Simple squamous epithelium, mesovarium, human, H&E Facilitates the movement of the viscera centrally located nucleus that is flattened and oval or spherical in shape 6

7 (B) lines the cardiovascular and lymphatic system (heart, blood vessels, lymphatic vessel linings), where it is known as ENDOTHELIUM Provides a physical barrier between the circulating blood and the subendothelial tissues Produces vasoactive agents that cause Constriction and relaxation of underlying vascular smooth muscles, thus affecting the blood pressure!!!!! 7

8 (C)-Alveoli (air sacs of lungs) of lungs diffusion of oxygen into blood vessels of lungs) 8

9 Present at sites of filtration (such as blood filtration in kidneys) glomerular (Bowman s) capsule of kidneys 9

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12 Single layer of cube-shaped cells; round, centrally located nucleus. Cuboidal cell shape is obvious when tissue is sectioned and viewed from the side Its main functions are Secretion and absorption. 12

13 Locations of the simple cuboidal epithelium lines kidney tubules Makes up secreting portion of some glands such as thyroid gland Ducts of some glands such as pancreas The smallest conducting bronchioles of the lung Read only Surface of Ovary lines anterior surface of capsule of lens of the eye forms pigmented epithelium at posterior surface of retina of the eye 13

14 lines kidney tubules 14

15 cuboidal cells (CC). 15

16 This photomicrograph shows two pancreatic ducts (PD) that are lined by a simple cuboidal epithelium 16

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18 CILIATED SIMPLE COLUMNAR EPITHELIUM Single layer of ciliated column like cells with oval nuclei near base of cells. Goblet cells are usually interspersed among ciliated columnar epithelia 18

19 Locations of the CILIATED SIMPLE COLUMNAR EPITHELIUM Lines some bronchioles (small tubes) of respiratory tract Uterine (fallopian) tubes Read only Some paranasal sinuses Central canal of spinal cord Ventricles of brain 19

20 Cilia help move oocytes expelled from ovaries through uterine (fallopian) tubes into uterus 20

21 SIMPLE COLUMNAR NONCILIATED Single layer of nonciliated column like cells with oval nuclei near base of cells; contains (1) columnar epithelial cells with microvilli at apical surface (2) goblet cells 21

22 Location Lines gastrointestinal tract (from stomach to anus), ducts of many glands, and gallbladder Function Secretion and absorption; larger columnar cells contain more organelles and thus are capable of higher level of secretion and absorption than are cuboidal cells 22

23 E.Pseudostratified columnar Pseudostratified epithelium:(pseudo= false) Tissue appears to be several layers but is really a single layer. Cells nuclei lie at different levels and cells appear to have multiple layers. All its cells rest on the base but not all of them reach the surface. 23

24 1. Ciliated: Form of cells with cilia and Goblet cells. Locations: Lines airways of most of upper respiratory tract. Functions: Secretes mucus that traps foreign particles. 2.Nonciliated: Contains cells without cilia and lack goblet cells. Locations: Lines larger ducts of many glands & epididymis. Functions: Absorption and protection. د. درويش بدران د. ماهر الحديدي د.امجد الشطرات و 24

25 Stratified epithelium Two or more layers of cells cells in apical layer and several layers deep to it are squamous cells in deeper layers vary from cuboidal to columnar. As basal cells divide, daughter cells arising from cell divisions push upward toward apical layer. As daughter cells move toward surface and away from blood supply in underlying connective tissue, they become dehydrated and less metabolically active. Tough proteins predominate as cytoplasm is reduced, and cells become tough, hard structures that eventually die. At apical layer, after dead cells lose cell junctions they are sloughed off, but they are replaced continuously as new cells emerge from basal cells. 25

26 II. Stratified epithelium Types: a. Stratified squamous keratinized Nonkeratinized. b. Stratified cuboidal epithelium. c. Stratified columnar epithelium. d. Transitional epithelium. 26

27 A-Stratified squamous epithelium Two types: Keratinized (dry). Nonkeratinized (wet). Keratinized stratified squamous epithelium develops tough layer of keratin in apical layer of cells and several layers deep to it (Keratin is a tough, fibrous intracellular protein that helps protect skin and underlying tissues from heat, microbes, and chemicals.) Relative amount of keratin increases in cells as they move away from nutritive blood supply and organelles die 27

28 Keratinized stratified squamous : 28

29 Covers dry surfaces such as epidermis of skin (superficial layer of the skin). Form tough layer of keratin (tough protein) between surface cells. Functions: Protect skin and underlying tissues from heat, microbes, chemicals and water loss. 29

30 Nonkeratinized stratified squamous Surface layers contain small amount of keratin and always wet. Location: Lines wet surfaces as lining of mouth, esophagus, part of epiglottis, part of pharynx, and vagina) and covers tongue Function: Protection against scratch, water loss, ultraviolet radiation, and foreign invasion. Both types form first line of defense against microbes. 30

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32 STRATIFIED CUBOIDAL EPITHELIUM Location Ducts of adult sweat glands and esophageal glands, part of male urethra. 32

33 STRATIFIED COLUMNAR EPITHELIUM Basal layers usually consist of shortened, irregularly shaped cells; only apical layer has columnar cells; uncommon. Location Lines part of urethra; large excretory ducts of some glands, such as esophageal glands; small areas in anal mucous membrane; part of conjunctiva of eye. 33

34 TRANSITIONAL EPITHELIUM Variable appearance (transitional) In relaxed or unstretched state, looks like stratified cuboidal epithelium, except apical layer cells tend to be large and rounded. As tissue is stretched, cells become flatter, giving the appearance of stratified squamous epithelium. Multiple layers and elasticity make it ideal for lining hollow structures (urinary bladder) subject to expansion from within Locations: Urinary bladder, ureter. Functions: Allow the organ to stretch and protection from rupturing. 34

35 Location Lines urinary bladder and portions of ureters and urethra Function Allows urinary organs to stretch and maintain protective lining while holding variable amounts of fluid without rupturing 35

36 Celiac disease also called gluten-sensitive enteropathy is a disorder of the small intestine in which one of the first pathologic changes is loss of the microvilli brush border of the absorptive cells This is caused by an immune reaction against the wheat protein gluten during its digestion, which produces diffuse enteritis (intestinal inflammation), changes to the epithelial cells leading to malabsorption, and eventually to pathologic changes in the intestinal wall. The malabsorption problems and structural changes are reversible when gluten is removed from the diet. 36

37 Several mutations have been described in the proteins of the cilia and flagella. They are responsible for the immotile cilia syndrome (Kartagener syndrome), whose symptoms are chronic respiratory infections caused by the lack of the cleansing action of cilia in the respiratory tract and immotile spermatozoa, causing male infertility 37

38 Myoepithelial cells Sometimes termed basket cells Fusiform or stellate in shape Contain actin and myosin filaments and contract when stimulated by nervous or endocrine signals. They surround the secretory portions and ducts of some glands, e.g.mammary, lacrimal, salivary and sweat glands Their contraction assists the initial flow of secretion into larger conduits. 38

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40 surface epithelium and its underlying connective tissue are regarded as a functional unit called a membrane. The two types of membrane are mucus membrane and serous membrane. Mucus membrane, also called mucosa, lines those cavities that connect with the outside of the body, namely, the alimentary canal, the respiratory tract, and the geni-tourinary tract. It consists of surface epithelium (with or without glands), a supporting connective tissue called the lamina propria, Serous membrane, also called serosa, lines the peritoneal, pericardial, and pleural cavities. These cavities are usually described as closed cavities of the body, although in the female the peritoneal cavity communicates with the exterior via the genital tract. Structurally, the serosa consists of a lining epithelium, the mesothelium, a supporting connective tissue, and a basement membrane between the two. Serous membranes do not contain glands, but the fluid on their surface is watery. 40