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Visual Anatomy & PhysiologyFirst Edition
Martini & Ober
Chapter 4
Epithelial Tissues
Lecture 9
2
Lecture Overview
• Introduction to Tissues
• Epithelial Tissues– Location– General characteristics– Functions– Classification
• Glandular Epithelium
3
Where are Tissues in Our Organizational Scheme?
Figure from: Hole’s Human A&P, 12th edition, 2010
4
Introduction to 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)
Tissue - a group of cells working together to perform one or more specific functions
Histology – the microscopic study of tissues
5
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’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
6
Functions of Epithelial Tissue• Physical protection
– Protect from abrasion, dehydration, and destruction by chemical or biological agents
• Control of permeability – Secretion– Absorption– Filtration
• Provide sensation– Extensively innervated by sensory nerves– May function in senses (smell, taste, etc.)
• Provide specialized secretions (glands)
7
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
8
Characteristics of Epithelial TissueSpecialized Contacts
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
9
Characteristics of Epithelial TissuePolarity
Outside surface – note modifications
Inner surface – attached to underlying tissue by a basement membrane
Notice the polarity and differential distribution of the cellular organelles
Figures from: Martini Visual A&P, 1st edition, 2011
10
Characteristics of Epithelial TissueAvascularity 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
11
Characteristics of Epithelial TissueCellularity
- Cells are bound closely together
- Little intercellular material
- May form sheets; cells usually slough off in sheets
Figure from: Hole’s Human A&P, 12th edition, 2010
12
Modifications of Epithelial Cells
Cilia – movement of substances
Microvilli – greatly increase absorptive (surface) area
Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001
13
Basal Lamina
Two components:
Lamina Lucida - glycoproteins and fine protein filaments - Barrier for passage of substances from underlying tissue into epithelium
Lamina Densa - bundles of coarse protein fibers - gives basal lamina its strength
Formerly called: Basement membrane
Figure from: Martini, Fundamentals of Anatomy & Physiology, Benjamin Cummings, 2004
Lamina = thin layer
14
Classification of Epithelial Tissues
• Shape– Squamous (Thin, flat, irregular in shape)– Cuboidal (Square 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
Epithelial tissues are classified according to both their:
15
Epithelial Tissues
Simple squamous –• single layer of flat cells• substances pass easily through• line air sacs of lung, blood vessels, lymphatic vessels• reduce friction, absorption/secretion
Mesothelium – lines ventral body cavities
Endothelium – lines blood vessels
Figure from: Hole’s Human A&P, 12th edition, 2010
16
Epithelial Tissues
Simple cuboidal –• single layer of cube-shaped cells
• line kidney tubules
• cover ovaries
• line ducts of some glands
• limited protection, secretion/absorption
17
Epithelial Tissues
Simple columnar –• single layer of elongated cells• sometimes possess cilia or microvilli• often have goblet cells• line uterus, stomach, intestines• protection, secretion, absorption
Figure from: Hole’s Human A&P, 12th edition, 2010
18
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
19
Epithelial Tissues
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)
Figure from: Hole’s Human A&P, 12th edition, 2010
20
Epithelial Tissues
Stratified cuboidal – • 2-3 layers• cube-shaped cells• line ducts (rare) of mammary glands, sweat glands, salivary glands, and the pancreas• protection, secretion, absorption
Figure from: Hole’s Human A&P, 12th edition, 2010
21
Epithelial Tissues
Stratified columnar –• top layer of elongated cells• cube-shaped cells in deeper layers• line vas deferens, male urethra, and part of pharynx• protection
Figure from: Hole’s Human A&P, 12th edition, 2010
22
Epithelial Tissues
Transitional –• many cell layers
• cube-shaped and elongated cells
• line urinary bladder, ureters, and part of urethra
Located in places where acute stretching occurs
Figure from: Hole’s Human A&P, 12th edition, 2010
23
Glandular Epithelium
Composed of cells that are specialized to produce and secrete substances
Endocrine glands are ductless – secrete directly into the bloodExocrine 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.
24
Structural Types of Exocrine Glands
Classified by:
1. Shape of secretory portion of gland
2. Branching pattern of the duct
25
Exocrine Glands
Classified by:
1. Shape of secretory portion of gland
2. Branching pattern of the duct
26
Types of Glandular SecretionsMerocrine glands
• fluid product• exocytosis• salivary glands• pancreas• sweat glands
Apocrine glands • cellular product• apical portions of cells• mammary glands• ceruminous glands
Holocrine glands• secretory products• whole cells• sebaceous glands in hair follicles
Figure from: Hole’s Human A&P, 12th edition, 2010
27
Membranes
Serous• line body cavities that lack openings to outside• reduce friction• inner lining of thorax and abdomen• cover organs of thorax and abdomen• secrete serous fluid
Mucous• line tubes and organs that open to outside world• lining of mouth, nose, throat, digestive tract, etc.• secrete mucus
Cutaneous• covers body• skin
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.
Synovial• surround joint cavities
28
Epithelial Membranes
Figure from: Martini, Anatomy & Physiology, Prentice-Hall, 2001
Notice that each type of membrane is composed of TWO different types of tissues; epithelial and connective
29
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– Sensation– Secretion
• Characteristics of epithelial tissue include – Specialized contacts– Polarity– Avascularity– Regeneration– Cellularity
30
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)
31
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
32
Review
NAME OF ET DESCRIPTION STRUCTURE
LOCATION FUNCTION
SIMPLESQUAMOUS
a single layer of flattened cells
linings of air sacs, capillaries, lymph vessels, body cavities; covering ventral organs
diffusion, reduction of friction
SIMPLE CUBOIDAL
a single layer of cube-shaped cells with large centrally located nuclei
linings of kidney tubules, ducts of glands
absorption,secretion
SIMPLE COLUMNAR
a single layer of tall cells with basally located nuclei, goblet cells, & mucrovilli
lining of intestine protection,absorption,secretion
PSEUDO-STRATIFIEDCOLUMNAR
a single layer of tall cells with scattered nuclei, cilia, & goblet cells
lining of trachea,lining of fallopian tube
protection, secretion
33
Review
NAME OF ET DESCRIPTION STRUCTURE
LOCATION FUNCTION
STRATIFIEDSQUAMOUS
many layers of flattened cells
keratinized = epidermis;non-keratinized = lining of vagina, anus, throat, mouth
protection
TRANSITIONAL several layers of cells that change shape under pressure
lining of urinary bladder and ureters
Distensibility (able to stretch)
GLANDULAR simple cuboidal lining the ducts of glands
secretion