Histology of Epithelium and Glands PDF

HISTOLOGY OF BASIC TISSUES EPITHELUM AND GLANDS DR. VICTOR ANATOMY Its a French word which means weave or texture. Collection of cells together with intercellular substance to perform a similar function.  BASIC TISSUES OF BODY Epithelial Tissue Connectiv...

HISTOLOGY OF BASIC TISSUES EPITHELUM AND GLANDS DR. VICTOR ANATOMY Its a French word which means weave or texture. Collection of cells together with intercellular substance to perform a similar function.  BASIC TISSUES OF BODY Epithelial Tissue Connective Tissue Muscular Tissue Nervous Tissue  GENERAL FEATURES OF EPITHELIA It’s a collection of cells arranged in the form of sheet which covers the following: - External surface of the body - Internal surface of hollow viscera - Luminal surface of cavities - Also lines the ducts, glands & lies on a Basement membrane.  FUNCTIONS OF EPITHELIUM ▪ Protection of underlying tissues of the body from abrasion and injury ▪ Transcellular transport of molecules across the epithelial layers. ▪ Secretion of mucous, hormones, enzymes from various glands. ▪ Absorption of material from the lumen (e.g.; intestinal tract or certain kidney tubules). ▪ Control of movement of materials between body compartments via selective permeability of intercellular junction between epithelial cells. ▪ Detection of sensations via taste buds, retina of the eye and specialized hair cells in the ear ▪ Lubrication of Serous Cavities CLASSIFICATION OF EPITHELIAL TISSUE There are two types of epithelial tissue. 1) Simple Epithelial Tissue - consists of single layer of cells. 2) Compound Epithelial Tissue – consist of multi- layered or stratified. CLASSIFICATION OF EPITHELIUM UNILAYERED OR SIMPLE STRATIFIED OR EPITHELIUM MULTILAYERED EPITHELIUM Squamous epithelium Stratified squamous Columnar epithelium epithelium Cuboidal epithelium Transitional Pseudostratified epithelium columnar epithelium Stratified columnar and cuboidal epithelium SIMPLE SQUAMOUS EPITHELIUM  SIMPLE SQUAMOUS EPITHELIUM Thin layer of flat cells, width is more than the height resting on a basement membrane Nucleus is flat, seen as a bulge on the cell surface Thin layer of cytoplasm When seen from the surface it has polygonal outline Example: Pulmonary alveoli As endothelium in lymphatics, blood vessels Pleura, Pericardium, Peritoneum Loop of Henle, Parietal layer of Bowman's capsule Function: Mainly for the trans cellular diffusion of substances.  COLUMNAR EPITHELIUM Rectangular in shape, height is more than width Nucleus seen in the base of the cell Based on presence or absence of specialized structures on its surface Simple columnar epithelium Stomach and large intestine Ciliated columnar epithelium Respiratory tract, efferent duct of testis, uterus Microvillus (irregular) seen as Striated border type of columnar epithelium Small intestine Microvillus (regular) seen as Brush border type of columnar epithelium Gall bladder Secretory columnar cells Stomach and intestines – goblet cells COLUMNAR EPITHELIUM  CUBOIDAL EPITHELIUM Single layer, height and width are same resting on basement membrane Nucleus centrally placed and circular Seen in the germinal epithelium of ovary, thyroid follicles, inner surface of the lens, pigment layer of retina, renal tubules PSEUDOSTRATIFIED COLUMNAR EPITHELIUM Single layer of cells with different heights resting on common basement membrane. Only some cells reach the surface of the epithelium Nucleus are located at different levels, giving the impression of a stratified epithelium even though it is composed of single layer of cells. Found in the male urethra, epididymis and large excretory ducts of glands PSEUDOSTRATIFIED CILIATED COLUMNAR EPITHELIUM Trachea and large bronchi PSEUDOSTRATIFIED COLUMNAR EPITHELIUM  STRATIFIED SQUAMOUS EPITHELIUM Features: Cells are many layered. Basal cells are –Columnar Intermediate cells – Cuboidal Surface cells – Flattened (Squamous) Seen in areas where there is maximum friction cells require constant replacement ⚫Two types: ⚫ Non-keratinized stratified squamous epithelium All cells are living and have nuclei up to the surface ⚫ Keratinized stratified Squamous epithelium The superficial cells have lost their nuclei so they are dead scales converted into a material called keratin. ⚫Twotypes: ⚫ Non-keratinized stratified squamous epithelium ⚫ Lining of the mouth, oral pharynx, esophagus, true vocal folds, vagina and epiglottis. ⚫ Surface is usually wet. ⚫ Keratinized stratified Squamous epithelium ⚫ Surface is dry ⚫ Skin of the whole body STRATIFIED CUBICAL EPITHELIUM FEATURES: It consist of several layers of cells of which superficial ones are cuboidal Chief Distribution: Ducts of some glands STRATIFIED COLUMNAR EPITHELIUM FEATURES: Cells are arranged in many layers , superficial ones are columnar Chief Distribution:conjunctiva and cavernous parts of male urethra  TRANSITIONAL EPITHELIUM Multilayered arrangement of cells (usually 3-5) It varies with distention and relaxation of organ Histological difference by layer: Deepest layer – columnar or cuboidal cells Middle layer – pear shaped cells, tip towards basement membrane. On surface – umbrella-shaped or large polyhedral cells Seen in the ureter, urinary bladder, renal pelvis and calyces and part of the urethra. HENCE IT IS CALLED UROTHELIUM. TRANSITIONAL EPITHELIUM SQUAMOUS EPITHELIUM LUNG PARENCHYMA CUBOIDAL EPITHELIUM THYROID GLAND SIMPLE COLUMNAR EPITHELIUM STOMACH  COLUMNAR EPITHELIUM WITH BRUSH BORDER GALL BLADDER CILIATED COLUMNAR EPITHELIUM FALLOPION TUBE GOBLET CELLS OF LARGE INTESTINE PSEUDOSTRATIFIED COLUMNAR CILIATED EPITHELIUM TRACHEA STRATIFIED COLUMNAR EPITHELIUM LARGE DUCT STATIFIED SQUAMOUS NON-KERATINISED EPITHELIUM OESOPHAGUS STRATIFIED SQUAMOUS KERATINISED EPITHELIUM SKIN TRANSITIONAL EPITHELIUM URETER Glandular Epithelia Definition: Glands are the structures which develop as an outgrowth from epithelium lined surfaces. Specialized epithelial cells, arranged as single or groups of cells, to perform a secretory function. Glandular Epithelium Glandular Epithelium = Columnar epithelium + goblet cells Columnar and Cuboidal epithelial cells often become specialized as gland cells which Synthesize and secrete substances like enzymes, hormones, milk, mucus, sweat, wax and saliva. Some parts of the glandular epithelium consist of large number of goblet cells that there are only a few normal epithelial cells left. Glands can be classified as 1.Unicellular glands consist of single, isolated glandular cells such as the goblet cells. seen along with other non-secreting epithelial cells E.g. Intestines 2.Multicellular glands Are composed of clusters of cells. Develops as a diverticula from epithelial surface. Distal part develops into secretory part. Proximal part form the ducts which opens into epithelial surface. Unicellular gland  Goblet cell Unicellular gland Multicellular gland Epithelia of secretory portion of a glands has specialised structures depending on its secretions 1.Protein secretion well-developed ER, supranuclear Golgi apparatus 2.Mucin secretion well-developed Rough ER, Golgi complex 3.Steroid secretion extensive smooth ER, prominent mitochondria On the basis of the manner in which their secretions are poured out of the cell, Exocrine gland can be called as: 1.MEROCRINE Secretions are thrown by exocytosis, cell remaining intact, e.g. pancreatic exocrine glands 2.APOCRINE Some part of a cell is lost along with its secretions e.g. Apocrine sweat glands 3.HOLOCRINE Entire cell degenerates while discharging its secretions. E.g. Sebaceous glands. Depending on the type of secretions exocrine gland can be called as 1.Mucous glands (mucopolysaccharide, seen collect in the apex of the cell so the nucleus is pushed to the base) Eg:sublingual salivary gland 2.Serous glands (protein in nature, cytoplasm granular, nucleus is central) Eg:parotid salivary gland Exocrine and Endocrine glands THOSE GLANDS which Pour secretions on to the epithelial surface through ducts is 1.EXOCRINE GLAND or external secreting gland Loose contact with their epithelium and pour secretions into the blood 2.ENDOCRINE GLAND or internal secreting gland or ductless gland EXOCRINE GLAND WHEN ALL THE SECRETIONS OF THE EXOCRINE GLAND are Sent through one duct –1. Simple gland Sometimes number of secreting glands, each group with their own duct, these ducts unite to form larger ducts which ultimately drain to epithelial surface (via these larger ducts) -2. Compound gland Simple and Compound EXOCRINE gland has secretory cells arranged in various forms: Tubular- straight, branched or coiled Rounded - sacs or acini Flask shaped - called alveoli Combination of the above Based on this exocrine glands can be classified as: 1.Unicellular 2.Simple tubular 3.Simple alveolar or acinar 4.Compound tubular 5.Compound alveolar 6.Compound tubulo-alveolar 1.Simple tubular gland 2.Simple straight tubular gland Compound Tubular Gland The kidney is an example. Secretory units are tubular provided with a branching duct system. The pointer in this indicates bifurcation of a portion of the duct system Endocrine glands Endocrine Gland Endocrine glands are characterized by the absence of a duct system. The secretions of endocrine cells are called hormones. Hormones travel through blood to target cells whose functioning they may influence profoundly Endocrine Gland The cells in most endocrine tissues and organs are arranged into cords and clumps, and are surrounded by an extensive capillary network. Eg: hypophysis or pituitary gland , thyroid gland, adrenal (suprarenal)glands, and parathyroid glands Applied Anatomy Tumours arising from epithelia A tumour (or neoplasm) can arise from any tissue if there is uncontrolled growth of cells. Such a tumour may be benign, when it remains localised; or may be malignant. A malignant growth invades surrounding tissues. Cells of the tumour can spread to distant sites (through lymphatics or through the bloodstream) and can start growing there producing what are called secondaries or metastases Applied Anatomy A malignant tumour arising from an epithelium is called a carcinoma. If it arises from a squamous epithelium it is a squamous cell carcinoma; and if it arises from glandular epithelium it is called an adenoma.