Visual Anatomy & Physiology First Edition Martini & Ober Chapter 4 Epithelial Tissues Lecture 9 Lecture Overview • Introduction to Tissues • Epithelial Tissues – Location – General characteristics – Functions – Classification • Glandular Epithelium 2 Where are Tissues in Our Organizational Scheme? Figure from: Hole’s Human A&P, 12th edition, 2010 3 1 Introduction to Tissues Tissue - a group of cells working together to perform one or more specific functions Histology – the microscopic study of tissues Four primary types of tissues found in the adult : 1. Epithelial (covering/lining, protection, glands) [ pl. epithelia] 2. Connective (binding together, support, transport, energy) 3. Muscle (movement, heat production) 4. Nervous (information and short-term control) 4 Major Types of Epithelial Tissues • Covering and Lining Epithelium – External Surfaces, e.g., skin – Internal surfaces • Communicate with outside, e.g., digestive, respiratory, reproductive and urinary tracts •Don’iihidhi’t communicate with outside, e.g., chest cavity, abdominal cavity, endothelium of blood vessels and heart • Glandular Epithelium – Often lie in clusters deep to covering and lining epithelium – Specialized for secretion into ducts, on to a surface, or into the blood 5 Functions of Epithelial Tissue • Physical protection – Protect from abrasion, dehydration, and destruction by chemical or biological agents • Control of permeability – Secretion – Absorpt ion – Filtration • Provide sensation – Extensively innervated by sensory nerves – May function in senses (smell, taste, etc.) • Provide specialized secretions (glands) 6 2 Characteristics of Epithelial Tissue •Specialized contacts with other cells •Polarity (different ends of cell do different things) •Avascularity (no blood supply) •Regeneration (can divide to make new cells) •Cellularity (lots of cells in close contact) Remember: Epithelial tissues always have a free surface and a basement membrane 7 Characteristics of Epithelial Tissue Specialized Contacts Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 8 Characteristics of Epithelial Tissue Polarity Outside surface – note modifications Inner surface – attached to underlying tissue by a st basement membrane Figures from: Martini Visual A&P, 1 edition, 2011 Notice the polarity and differential distribution of the cellular organelles 9 3 Characteristics of Epithelial Tissue Avascularity and Regeneration •Does not contain blood vessels (avascular) – Nutrients must be obtained by • Diffusion from underlying tissue (125 µm limit) • Absorption from free surface • High rate of cell division and replacement – Lost cells are continually replaced by dividing epithelial stem cells – Rate of cell division (mitotic rate) is much higher than other tissues 10 Characteristics of Epithelial Tissue Cellularity Figure from: Hole’s Human A&P, 12th edition, 2010 - Cells are bound closely together - Little intercellular material - May form sheets; cells usually slough off in sheets 11 Modifications of Epithelial Cells Cilia – movement of substances Microvilli – greatly increase absorptive (surface) area 12 Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001 4 Basal Lamina Formerly called: Basement membrane Two components: Lamina Lucida - glycoproteins and fine protein filaments - BifBarrier for passage o fbtf substances from underlying tissue into epithelium Lamina Densa - bundles of coarse protein fibers Lamina = thin layer - gives basal lamina its strength 13 Figure from: Martini, Fundamentals of Anatomy & Physiology, Benjamin Cummings, 2004 Classification of Epithelial Tissues Epithelial tissues are classified according to both their: • Shape – Squamous (Thin, flat, irregular in shape) – Cuboidal ((qSquare or cuboidal) – Columnar (Rectangular, tall) • Type of layering (stratification) – Simple (one layer) – Stratified (two or more layers) – Note that classification of stratified epithelium is based on the shape of the superficial, not deep, layers 14 Epithelial Tissues Figure from: Hole’s Human A&P, 12th edition, 2010 Simple squamous – Mesothelium – • single layer of flat cells lines ventral body • substances pass easily through cavities • line air sacs of lung, blood vessels, lymphatic vessels Endothelium – • reduce friction, absorption/secretion lines blood vessels 15 5 Epithelial Tissues Simple cuboidal – • single layer of cube- shaped cells • line kidney tubules • cover ovaries • line ducts of some glands • limited protection, secretion/absorption 16 Epithelial Tissues Figure from: Hole’s Human A&P, 12th edition, 2010 Simple columnar – • single layer of elongated cells • sometimes possess cilia or microvilli • often have goblet cells • line uterus, stomach, intestines • protection, secretion, absorption 17 Epithelial Tissues Pseudostratified columnar – • single layer of elongated cells • appear stratified, but they ARE NOT • all cells attach to basement membrane; some do not reach surface • often have cilia and goblet cells • line respiratory passageways • protection, secretion 18 6 Epithelial Tissues Figure from: Hole’s Human A&P, 12th edition, 2010 Stratified squamous – • many cell layers • top cells are flat • can accumulate keratin • outer layer of skin • line oral cavity, throat, vagina, and anal canal Main function is protection (abrasions, pathogens, chemicals) 19 Epithelial Tissues Figure from: Hole’s Human A&P, 12th edition, 2010 Stratified cuboidal – • 2-3 layers • cube-shaped cells • line ducts (rare) of mammary glands, sweat glands, salivary glands, and the pancreas • protection, secretion, absorption 20 Epithelial Tissues Figure from: Hole’s Human A&P, 12th edition, 2010 Stratified columnar – • top layer of elongated cells • cube-shaped cells in deeper layers • line vas deferens, male urethra, and part of pharynx • protection 21 7 Epithelial Tissues Figure from: Hole’s Human A&P, 12th edition, 2010 Transitional – • many cell layers • cube-shaped and elongated cells • line urinary bladder, ureters, and part of urethra Located in places where acute stretching occurs 22 Glandular Epithelium Composed of cells that are specialized to produce and secrete substances Endocrine glands are ductless – secrete directly into the blood Exocrine glands have ducts – secrete into a duct or on to a surface Unicellular exocrine gland • composed of one cell • Example: goblet cell Multicellular exocrine gland • composed of many cells • Examples: sweat glands, sebaceous glands, salivary glands, etc. 23 Structural Types of Exocrine Glands Classified by: 1. Shape of secretory portion of gland 2. Branching pattern of the duct 24 8 Exocrine Glands Classified by: 1. Shape of secretory portion of gland 2. Branching pattern of the duct 25 Types of Glandular Secretions Figure from: Hole’s Human A&P, 12th edition, 2010 Merocrine glands Apocrine glands Holocrine glands • fluid product • cellular product • secretory products • exocytosis • apical portions of cells • whole cells • salivary glands • mammary glands • sebaceous glands • pancreas • ceruminous glands in hair follicles • sweat glands 26 Membranes A membrane is a combination of epithelium and connective tissue that covers and protects other structures and tissues. Technically, then, a membrane is an organ. Serous Mucous • line body cavities that • line tubes and organs lklack open ings to ou tidtside tha t open ttidldto outside world • reduce friction • lining of mouth, nose, • inner lining of thorax and throat, digestive tract, etc. abdomen • secrete mucus • cover organs of thorax and abdomen Synovial • secrete serous fluid • surround joint cavities Cutaneous • covers body • skin 27 9 Epithelial Membranes Notice that each type of membrane is composed of TWO different types of tissues; epithelial and connective Figure from: Martini, Anatomy & Physiology, 28 Prentice-Hall, 2001 Review of Epithelial Tissues • Tissue - a group of cells working together to perform one or more specific functions • Epithelial tissues are covering, lining, and glandular tissues that function in – Physical protection – Control of permeability – StiSensation – Secretion • Characteristics of epithelial tissue include –Specialized contacts –Polarity –Avascularity –Regeneration –Cellularity 29 Review of Epithelial Tissues • Attached to underlying tissue by a basal lamina (basement membrane) • Classified according to shape and number of layers • Epithelial tissue always has a free surface • Glands are specialized epithelium – Secrete on to a surface – Secrete into a duct (exocrine) – Secrete into the blood (endocrine) 30 10 Review of Epithelial Tissues • Exocrine glands have several different mechanisms of secretion – Merocrine • Release of product from vesicles by exocytosis • Most common mode of secretion • Example: watery sweat used to cool skin – Apocrine • Loss of cytoplasm containing secretion • Apical portion of cytoplasm is shed • Example: thick, sticky underarm perspiration – Holocrine • Entire cell is packed with secretion and then bursts • Destroys cell • Example: sebaceous glands associated with hair follicles 31 Review NAME OF ET DESCRIPTION LOCATION FUNCTION STRUCTURE SIMPLE a single layer of linings of air sacs, diffusion, reduction of SQUAMOUS flattened cells capillaries, lymph friction vessels, body cavities; covering ventral organs SIMPLE a single layer of cube- linings of kidney absorption, CUBOIDAL shaped cells with tubules, ducts of secretion large centrally glands located nuclei SIMPLE a single layer of tall lining of intestine protection, COLUMNAR cells with basally absorption, located nuclei, secretion goblet cells, & mucrovilli PSEUDO- a single layer of tall lining of trachea, protection, secretion STRATIFIED cells with scattered lining of fallopian tube COLUMNAR nuclei, cilia, & goblet cells 32 Review NAME OF ET DESCRIPTION LOCATION FUNCTION STRUCTURE STRATIFIED many layers of keratinized = protection SQUAMOUS flattened cells epidermis; non-keratinized = lining of vagina, anus, throat, mouth TRANSITIONAL several layers of lining of urinary Distensibility (able cells that change bladder and ureters to stretch) shape under pressure GLANDULAR simple cuboidal lining the ducts of secretion glands 33 11.