Epithelial Tissue in the Body
Epithelial tissue covers the inner and outer surfaces of the body, forming a protective barrier. It is a vital tissue composed of tightly adhered cells resting on the basement membrane, showcasing different types of junctions and surface modifications to fulfill various functions such as protection, absorption, secretion, and sensory perception. Explore the features, functions, and classification of epithelial tissue to gain insights into its importance within the body.
Download Presentation
Please find below an Image/Link to download the presentation.
The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author.If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.
You are allowed to download the files provided on this website for personal or commercial use, subject to the condition that they are used lawfully. All files are the property of their respective owners.
The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author.
E N D
Presentation Transcript
EPITHELIAL TISSUE EPITHELIAL TISSUE EPITHELIUM- THE SURFACE OF THE BODY(INNER&OUTER) AND INNER SURFACES OF TUBULAR STRUCTURES WITH IN THE BODY ARE COVERED BY A LAYER OF CELLS THAT RESTS ON THE BASEMENT MEMBRANE. SUCH A COVERING LAYER IS CALLED EPITHELIUM. EPITHELIUM IS A BASIC TISSUE OF BODY THAT CONSISTS OF TIGHTLY ADHERED CELLS CALLED EPITHELIAL CELLS.
FEATURES OF EPITHELIUM FEATURES OF EPITHELIUM IT CONSISTS OF LAYERS OF CELLS THAT COVER BODY SURFACES. IT IS AN AVASCULAR STRUCTURE. EPITHELIAL CELLS REST ON BASEMENT MEMBRANE. EPITHELIAL CELLS SHOW VARIOUS TYPES OF JUNCTIONS WITH ADJACENT CELLS AND BASEMENT MEMBRANE. IT SHOWS SURFACE MODIFICATIONS AS PER FUNCTIONAL NEED.eg MICROVILLI IN INTESTINE INCREASE ABSORPTIVE SURFACE AREA. IT UNDERGOES MITOSIS AND CAN REGENERATE DAMAGED PORTIONS.
FUNCTIONS OF EPITHELIUM FUNCTIONS OF EPITHELIUM PROTECTION. BARRIER- IN THE SKIN EPITHELIUM(CALLED EPIDERMIS) ACTS AS A MECHANICAL BARRIER AND MAY PERMIT SELECTIVE SUBSTANCES TO CROSS IT.eg EPIDERMIS PERMITS ENTRY OF SOME LIPID SOLUBLE SUBSTANCE(OINTMENTS).AND PREVENTS ENTERY OF VIRUSES. ABSORPTION-IN INTESTINE. SECRETION/EXCRETION- EPITHELIUM CAN SYNTHESIZE AND AND SECRETE SOME PRODUCT.eg IN SALIVARY GLAND,EPITHELIUM IS INVOLVED IN SALIVA SECRETION. SENSORY PERCEPTION- EPITHELIUM IS INVOLVED IN RECEIVING SENSORY SIGNALS FROM EXTERNAL ENVIRONMENT.eg EPITHELIUM OF TONGUE(TASTE BUDS) ARE INVOLVED IN PERCEPTION OF TASTE SENSATION.
CLASSIFICATION OF EPITHELIA CLASSIFICATION OF EPITHELIA SIMPLE EPITHELIUM- HAS ONLY ONE LAYER OF CELLS. STRATIFIED EPITHELIUM- HAS TWO OR MORE LAYER OF CELLS. PSEUDOSTRATIFIED EPITHELIUM- HAS ONE LAYER OF CELLS RESTING ON BASAL LAMINA BUT SOME OF THESE CELLS DO NOT EXTEND UP TO FREE SURFACE OF EPITHELIUM. SIMPLE EPITHELIUM- IS CLASSIFIED IN TO THREE GROUPS BASED ON SHAPE OF CELLS AS FOLLOWS. SIMPLE SQUAMOUS EPITHELIUM- SIMPLE SQUAMOUS EPITHELIUM IS COMPOSED OF A FLATTENED POLYGONAL CELLS. THESE CELLS HAVE THIN LAYER OF CYTOPLASM STAINED WITH EOSIN(PINK).
CONTD. CONTD. NUCLEI OF THESE CELLS ARE ELONGATED,FLAT, AND PRODUCE BULGING ON CELL SURFACE.(NUCLEI ARE STAINED DARK WITH HEMATOXYLIN (VIOLET). FREE SURFACE OF SIMPLE SQUAMOUS EPITHELIAL CELL IS IRREGULAR OR POLYGONAL. SECTION OF CELL: IT LOOKS SIMILAR TO A HALF FRIED EGG(CONSIDER NUCLEUS AS YOLK AND CYTOPLASM AS EGG WHITE). LOCATIONS-LINING EPITHELIUM OF LUNG ALVEOLI,ENDOTHELIUM(LINING EPITHELIUM OF BLOOD AND LYMPHATIC VESSELS),ENDOCARDIUM(LINING EPITHELIUM OF HEART),MESOTHELIUM (LINING EPITHELIUM OF SEROUS CAVITIES OF BODY),PARIETAL CELLS OF BOWMANS CAPSULE AND CERTAIN PARTS OF NEPHRONS IN KIDNEY.
FUNCTIONS FUNCTIONS AS CELLS ARE VERY THIN IN SIMPLE SQUAMOUS EPITHELIUM,SMALL MOLECULES CAN EASILY CROSS THE EPITHELIUM.THUS,IT HELPS IN RAPID TRANSPORT OF SUBSTANCES,DIFFUSION OF GASES,AND FILTRATION OF FLUIDS.
SIMPLE CUBOIDAL EPITHELIUM SIMPLE CUBOIDAL EPITHELIUM IT IS COMPOSED OF A SINGLE LAYER OF CUBOIDAL CELLS HAVING EQUAL WIDTH AND HEIGHT. NUCLEI OF CUBOIDAL CELLS ARE ROUNDED,PLACED CENTRALLY IN CELLS. AS WIDTH OF CELLS IS EQUAL,THEIR NUCLEI ARE SEEN TO BE EQUALLY PLACED IN A SINGLE ROW. SURFACE VIEW: CELLS ARE POLYGONAL OR HEXAGONAL WHEN SEEN FROM FREE SURFACE. CUBOIDAL CELLS CONTAIN EOSINOPHILIC CYTOPLASM.
LOCATIONS LOCATIONS 1. LINING EPITHELIUM OF THYROID FOLLICLES 2. SMALLER DUCTS OF EXOCRINE GLAND 3. EPITHELIUM COVERING THE OVARY(GERMINAL EPITHELIUM) 4. CHOROID PLEXUS 5. INNER SURFACE OF LENS OF EYE BALL 6. PIGMENTED CELL LAYER OF RETINA 7. DUCT OF BARTHOLIN GLAND 8. DCT.
FUNCTIONS FUNCTIONS CELLS OF SIMPLE CUBOIDAL EPITHELIUM HAVE CYTOPLASM THAT CONTAINS REQUIRED MACHINERY FOR PROTEIN SYNTHESIS BUT DOES NOT HAVE WELL DEVELOPED GOLGI APPARATUS FOR STORAGE OF SYNTHESIZED PROTEINS AND THEIR SUBSTANCES. HENCE CUBOIDAL EPITHELIUM IS MAINLY INVOLVED IN TRANSPORT(ABSORPTION,EXCRETION),SYNTHESIS,AND SECRETION OF SUBSTANCES.
SIMPLE COLUMNAR EPITHELIUM SIMPLE COLUMNAR EPITHELIUM FEATURES- THESE CELLS HAVE MORE HEIGHT THAN THEIR WIDTH. CYTOPLASM- THESE CELLS HAVE ABUNDANT CYTOPLASM AS THESE CELLS ARE INVOLVED IN SYNTHESIS AND STORAGE OF METABOLITE. NUCLEI- ARE OVAL(ELONGATED) AND USUALLY PLACED IN BASAL REGION OF CELLS. LIGHTLY STAINED AND ALL NUCLEI ARE PLACED AT THE SAME LEVEL. SURFACE MODIFICATIONS-AT SOME LOCATIONS SHOWS CERTAIN SURFACE MODIFICATIONS. 1. CILIA-FALLOPIAN TUBE. 2. MICROVILLI: IN GIT,BILE DUCT,GALL BLADDER.IF VILLI ARE ARRANGED IN REGULAR MANNER,IT GIVES STRIATED BORDER APPEARENCE.IF VILLI ARE ARRANGED IRREGULARLY IT GIVES BRUSH BORDER APPEARENCE ON LIGHT MICROSCOPIC EXAMINATION.
LOCATIONS LOCATIONS LINING EPITHELIUM OF STOMACH,INTESTINE,AND GALL BLADDER. LINING EPITHELIUM OF UTERUS. SIMPLE CILIATED COLUMNAR EPITHELIUM- FALLOPIAN TUBE,CENTRAL CANAL OF SPINAL CORD, VENTRICLES OF BRAIN,SOME PART OF RESPIRATORY TRACT, EFFERENT DUCTULE OF TESTIS,PART OF MIDDLE EAR,EUSTACHIAN TUBE etc.
FUNCTIONS FUNCTIONS 1. SECRETORY FUNCTION- SECRETION OF ENZYMES,MUCUS. 2. ABSORPTIVE FUNCTION: ABSORPTION OF NUTRIENTS IN INTESTINE. 3. CILIARY BEATS: PROPULSION OF MUCUS IN RESPIRATORY TRACT AND OVA IN FALLOPIAN TUBE. 4. MICROVILLI-HELP TO INCREASE ABSORPTIVE SURFACE AREA OF CELLS IN GALL BLADDER AND INTESTINE.
PSEUDOSTRATIFIED EPITHELIUM PSEUDOSTRATIFIED EPITHELIUM FEATURES- PSEUDOSTRATIFIED EPITHELIUM CONSISTS OF CELLS THAT REST ON BASAL LAMINA AND ONLY SOME OF THESE CELLS REACH UP TO THE FREE SURFACE OF EPITHELIUM. THIS EPITHELIUM IS NOT TRUE STRATIFIED EPITHELIUM.IT APPEARS TO BE STRATIFIED. BECAUSE OF DIFFERENTIAL HEIGHT OF CELLS,THEIR NUCLEI LIE AT DIFFERENT LEVELS AND FORMS TWO TO THREE ROWS OF NUCLEI.
LOCATIONS LOCATIONS RESPIRATORY TRACT- IN RESPIRATORY TRACT, TALLEST CELLS OF EPITHELIUM SHOW CILIA ON THE FREE SURFACE.HENCE IT IS CALLED PSEUDOSTRATIFIED COLUMNAR EPITHELIUM. IN MALE REPRODUCTIVE TRACT- IN EPIDIDYMIS,PSEUDOSTRATIFIED COLUMNAR EPITHELIUM WITH STEREOCILIA(LONG MICROVILLI) IS PRESENT.IT HELPS IN ABSORPTION OF FLUID. PSEUDOSTRATIFIED COLUMNAR EPITHELIUM(NON CILIATED) IS PRESENT IN THE AUDITORY TUBE,DUCTUS DEFERENCE AND MEMBRANOUS AND PENILE URETHRA.
FUNCTIONS FUNCTIONS PROTECTION OF UNDERLYING STRUCTURES. CILIARY MOVEMENTS REMOVE THE MUCUS. STEREOCILIA HELP IN ABSORPTION OF FLUID. GOBLET CELLS SECRETE MUCUS. BASAL CELLS ACT AS STEM CELLS FOR REMAINING CELLS OF THE EPITHELIUM.
GOBLET CELLS GOBLET CELLS THESE ARE MUCUS SECRETING CELLS. RESPIRATORY EPITHELIUM,TERMINAL PART OF SMALL INTESTINE,AND LARGE INTESTINE SHOW GOBLET CELLS. GOBLET MEANS CUP WITH NARROW BEAK IN GREEK. SHAPE OF GOBLET CELLS- APICAL CUP SHAPED PORTION CONNECTED WITH BASAL STEM LIKE PART. GOBLET CELLS SHOW SECRETORY GRANULES IN UPPER PART OF CELL AND AND NUCLEUS AND OTHER CELL ORGANELLES IN BASAL PART OF CELLS.
FUNCTIONS FUNCTIONS SECRETION OF MUCUS. MUCUS PROTECTS UNDER LYING EPITHELIUM. LOCATIONS- RESPIRATORY EPITHELIUM,GIT,CONJUCTIVA OF UPPER EYE LID. CLINICAL CORELATION- 1. ALLERGIC ASTHUMA MAY RESULT IN EXCESS PRODUCTION OF MUCUS. 2. GOBLET CELLS CARCINOID-IS A TUMOUR FORMED BY PROLIFERATION OF GOBLET CELLS AND NEUROENDOCRINE CELLS IN GUT
STRATIFIED EPITHELIUM STRATIFIED EPITHELIUM FEATURES- CONSISTS OF SEVERAL LAYERS OF CELLS. BASAL CELL LAYER CONSISTS OF CUBOIDAL OR COLUMNAR CELLS THAT REST ON BASAL LAMINA. BASAL CELLS ACT AS STEM CELLS;THEY DIVIDE MITOTICALLY AND MIGRATE TO SUPERFICIAL CELL LAYERS. CELLS ABOVE BASAL LAYER GRADUALLY DECREASE IN SIZE AND BECOME FLAT(SQUAMOUS).NUCLEI OF SUPERFICIAL LAYERARE ELONGATED AND FLAT. BASED ON KERATINIZATION(DEAD CELL LAYER) STRATIFIED SQUAMOUS EPITHELIUM ARE OF TWO TYPES. 1. KERATINIZED STRATIFIED SQUAMOUS EPITHELIUM. 2. NON KERATINIZED STRATIFIED SQUAMOUS EPITHELIUM.
KERATINIZED STRATIFIED SQUAMOUS EPITHELIUM KERATINIZED STRATIFIED SQUAMOUS EPITHELIUM SUPERFICIAL CELLS SHOW KERATOHYALIN GRANULES IN THEIR CYTOPLASM. MOST SUPERFICIAL CELLS ARE DEAD.THEY DO NOT HAVE NUCLEI.SUCH DEAD CELL LAYER IS CALLED STRATUM CORNEUM. KERATINIZATION INDICATES DRYNESS OR FRICTION EXPOSED SURFACE. LOCATION-EPIDERMIS OF SKIN. FUNCTIONS- IT PROTECTS THE DEEPER STRUCTURES FROM MECHANICAL INJURIES, ACTS AS BARRIER AGAINST INFECTION,AND PREVENTS WATER LOSS.
NON KERATINIZED STRATIFIED SQUAMOUS NON KERATINIZED STRATIFIED SQUAMOUS EPITHELIUM EPITHELIUM THERE IS NO STRATUM CORNEUM. CELLS IN THE UPPERMOST LAYER ARE LIVE AND NUCLEATED. CELLS BECOME INCREASING FLATTENED AS ONE MOVE TOWARD THE SUPERFICIAL LAYER. THIS EPITHELIUM REMAINS ALWAYS MOIST. SUCH MOIST EPITHELIUM WITH UNDERLYING THIN CONNECTIVE TISSUE LAYER(LAMINA PROPRIA) IS CALLED MUCOSA. LOCATIONS: EPITHELIAL LINING OF ORAL CAVITY,OROPHARYNX,LARYNGOPHARYNX,OESOPHAGUS,VAGINA ,TONSIL,VOCAL FOLD AND CORNEA.
FUNCTIONS FUNCTIONS IT PROTECTS UNDERLYING STRUCTURES. AND IT ACTS AS A BARRIER AGAINST PATHOGENIC ORGANISMS. NOTE: EPITHELIUM COVERING THE TONGUE REMAINS MOIST ,BUT IT IS EXPOSED TO CONTINNOUS FRICTION.HENCE,THE TONGUE IS COVERED PARTLY BY KERATINIZED AND PARTLY BY NONKERATINIZED STRATIFIED SQUAMOUS EPITHELIUM. PARAKERATINIZED EPITHELIUM: IS SIMILAR TO KERATINIZED EPITHELIUM,EXCEPT THAT IN PARAKERATINIZED EPITHELIUM CELL NUCLEI ARE PRESENT IN STRATUM CORNEUM.EXAMPLE;MUCOSA ON HARD PALATE AND GINGIVA. VITAMIN A DEFICIENCY MAY LEAD TO KERATINIZATION OF NONKERATINIZED STRATIFIED SQUAMOUS EPITHELIUM.
STRATIFIED CUBOIDAL EPITHELIUM STRATIFIED CUBOIDAL EPITHELIUM IT CONSISTS OF TWO OR MORE LAYERS OF CELLS. CELLS OF SUPERFICIAL LAYER ARE CUBOIDAL IN SHAPE. LOCATIONS- SOME DUCTS OF SWEAT GLANDS,SALIVARY GLANDS,AND SEBACEOUS GLANDS. FUNCTIONS- IT ACTS AS A BARRIER AND PROVIDES PASSAGE FOR SECRETION.
STRATIFIED COLUMNAR EPITHELIUM STRATIFIED COLUMNAR EPITHELIUM IT IS A TWO LAYERED THICK EPITHELIUM. SUPERFICIAL CELLS ARE COLUMNAR. BASAL CELLS ARE CUBOIDAL AND REST ON BASAL LAMINA. LOCATIONS- EPITHELIAL LINING OF SOME DUCTS OF SALIVARY GLAND,FORNIX OF CONJUCTIVA,AND CAVERNOUS URETHRA. FUNCTIONS- IT PROVIDES PASSAGE FOR SECRETIONS AND ACTS AS BARRIER.
TRANSITIONAL EPITHELIUM TRANSITIONAL EPITHELIUM TRANSITIONAL EPITHELIUM LINES THE MAJOR PART OF URINARY PASSAGE; HENCE IT IS CALLED UROTHELIUM. CELL THICK NESS OF TRANSITIONAL EPITHELIUM DEPENDS ON STRETCHING. IN DISTENDED BLADDER,TRANSITIONAL EPITHELIUM LOOKS ONLY 2-3 CELL LAYER THICK,WHERE AS IN EMPTY BLADDER IT LOOKS 5-6 LAYER THICK. THUS TRANSITIONAL EPITHELIUM HAS EXTRA RESERVE OF CELL LAYER(NUMBER OF CELL LAYERS DECREASE ON STRETCHING). CELLS BECOME FLATTENED ON STRETCHING DUE TO DISTENSION OF BLADDER ON RELAXATION IN EMPTY BLADDER,CELLS BECOME CUBOIDAL OR POLYGONAL. HENCE THIS EPITHELIUM IS CALLED TRANSITIONAL EPITHELIUM. BASAL CELLS ARE CUBOIDAL AND REST ON BASAL LAMINA.
CONT. CONT. CELLS OF UPPER LAYER ARE POLYGONAL. CELLS OF MOST SUPERFICIAL LAYER ARE DOME SHAPED /UMBRELLA-SHAPED.SURFACE CELLS MAY SHOW MITOTIC ACTIVITY. LOCATION- RENAL PELVIS,CALYCES OF KIDNEY,URETER,URINARY BLADDER,PART OF URETHRA. FUNCTIONS- PROVIDES ABILITY OF DISTENSION TO URINARY BLADDER. ACTS AS A BARRIER.
