NTA Level 4 • Semester 1 • PST04103

Structure and Functions of Epithelial Tissues

Human Anatomy and Physiology • Source Session/Topic 4

Full source-text version: all educational wording from the extracted learning source is retained; only presenter/tutor metadata and web-layout noise are removed, while formatting is improved for readability.

Session 4: Structure and Functions of Epithelial Tissues

Total Session Time: 120 minutes+60 minutes assignment

Prerequisites

• None

Learning Tasks

By the end of this session students are expected to be able to:

• Define Epithelial Tissue

• Describe the Structure of Epithelial Tissues

• Classify Epithelial Tissues

• Explain Functions of Epithelial Tissues

Resources Needed:

• Flip charts, marker pens, and masking tape

• Black/white board, chalk and whiteboard markers

• Charts, OHP, Multimedia Projector, Computer, Pointer

SESSION OVERVIEW

SESSION CONTENTS

STEP 1: Presentation of Session Title and Learning Tasks (5 minutes)

READ or ASK students to read the learning tasks and clarify

ASK students if they have any questions before continuing

STEP 2: Definition of epithelial Tissues (15 minutes)

|Activity: Brainstorming (5 minutes) |

| |

|Ask students to brainstorm on the following questions: |

| |

|What is epithelial tissue? |

| |

|ALLOW few students to respond |

| |

|WRITE their responses on the flip chart/ board |

| |

|CLARIFY and SUMMARISE by using the content below |

Epithelial tissues are linings of the various passages inside the body.

STEP 3: Structure of Epithelial Tissues (15minutes)

General Structure of Epithelial Tissues

• Epithelium is a group of closely associated cells with scanty

intercellular materials that cover external and internal surfaces of the

body

• They form the covering of all body surfaces, line body cavities and

hollow organs, and are the major tissue in glands

• Epithelial tissues are widely spread throughout the body

• The cells in epithelial tissue are tightly packed together with no

intercellular material between the cells or very little intercellular

materials

• It also forms all glands including endocrine and exocrine glands

• The cells are attached to the underlying connective tissue known as the

basement membrane

• The basement membrane is a connective tissue structure where the

epithelial cells are attached

• Cells of epithelial tissue appear in different shapes and structure

• These differences reflect the functions of the epithelium

STEP 4: Classification of Epithelial Tissues (40minutes)

|Activity: brainstorming (20 minutes) |

| |

|Ask students to brainstorm on the following questions. |

| |

|What are the classes of epithelial tissues? |

| |

|ALLOW few students to respond? |

| |

|WRITE their responses on the flip chart/ board |

| |

|CLARIFY and SUMMARISE by using the content below |

| |

Classification according to the cell shape

• Squamous cells: are flat cells with an irregular flattened shape

• Cuboidal cells: have a shape similar to a cube, meaning its width is the

same size as its height

• Columnar cells: are taller than they are wide

Classification based on number of layers (Stratification)

o Simple epithelia

o Stratified epithelia

o Pseudostratified epithelia

Simple Epithelium

▪ Cells are organized in a single layer and therefore all cells are

attached to the basement membrane

▪ Because the shapes of the cells include possible function, they are

found in different organs depending on their function:

▪ There are three types of simple epithelium: Simple squamous

epithelium, Simple cuboidal epithelium, Simple columnar epithelium

Simple Squamous Epithelium

▪ All Squamous cells are flat cells with an irregular flattened shape

▪ It is a one-cell layer of simple squamous epithelium

▪ Forms a thin membrane and therefore it is found in places where

exchange of material from one compartment to the other occurs.

▪ Squamous cells can be found in the heart, blood vessels, lymph vessels

and alveoli of the lung

▪ They allow free diffusion

Simple Cuboidal Epithelium

▪ This consists of cube-shaped cells fitting closely together lying

on a basement membrane.

▪ Forms secretory cells, lining of the small ducts of the gland sand

it covers the outer surfaces of organs such as the ovaries and in

the kidney tubules

▪ Are actively involved in secretion, absorption and excretion

Simple Columnar Epithelium

▪ This is formed by a single layer of cells, rectangular in shape lying

on a basement membrane.

▪ It is found lining the organs of the alimentary tract.

▪ Consists of mixture of cells, some absorb the products of digestion and

others secrete mucus.

Stratified Epithelia

• Consists of several layers of cells of various shapes

• The superficial layers grow up from below

• Basement membranes are usually absent

• The main function of compound epithelium is to protect underlying

structures

• There are two types: Stratified and transitional

Stratified squamous epithelium

• Consists of several layers of cells of different shapes

• The cells are arranged into superficial, intermediate and basal (deep)

layers

• In the deepest layers the cells are mainly columnar and, as they grow

towards the surface, they become flattened.

• It is the main protective epithelium of the body external surface for

example in the skin it forms the epidermis

• There are two types: Non keratinized stratified epithelium and

Keratinized stratified epithelium

o Keratinized stratified epithelium

▪ Refers to cells that has become hardened and died.

▪ The cells have a tough fibrous protein called keratin that helps

protect the skin and underlying tissues from heat, microbes and

chemicals.

▪ It is found on dry surfaces that are subject to wear and tear such

as skin, hair and nails.

o Non keratinized stratified epithelium

▪ Does not contain keratin and consists of cells which are not dead

▪ It is found on wet surfaces that may be subjected to wear and tear

but are protected from drying, for example conjunctiva of the eyes,

and lining of the mouth, pharynx, the oesophagus and vagina. It

provides mechanical protection from injury

[pic]Source: SEER Training Modules, 2003

Figure 4.1: Types of epithelium

STEP 5: General Functions of Epithelial Tissues (25 minutes)

|Activity: Buzzing (5 minutes) |

| |

|ASK students to pair up and buzz on the following question for 5 |

|minutes |

| |

|What are the functions of epithelial tissues? |

| |

|ALLOW few pairs to respond and let other pairs to add on points not |

|mentioned |

| |

|WRITE their response on the flip chart/board |

| |

|CLARIFY and SUMMARIZE by using the content below |

General Functions of Epithelial Tissue

• Protection

o Epithelial cells from the skin protect underlying tissue from mechanical

injury, harmful chemicals, invading bacteria and from excessive loss of

water

• Sensation

o Sensory stimuli penetrate specialized epithelial cells

o Specialized epithelial tissue containing sensory nerve endings is found

in the skin, eyes, ears, nose and on the tongue

• Secretion

o In glands, epithelial tissue is specialized to secrete specific chemical

substances such as enzymes, hormones and lubricating fluids

• Absorption

o Certain epithelial cells lining the small intestine absorb nutrients from

the digestion of food

• Excretion

o Epithelial tissues in the kidney excrete waste products from the body and

reabsorb needed materials from the urine

o Sweat is also excreted from the body by epithelial cells in the sweat

glands

• Diffusion

o Simple epithelium promotes the diffusion of gases, liquids and nutrients

STEP 6: Key Points (5 minutes)

• The term "epithelium" refers to layers of cells that line hollow organs

and glands

• It is also those cells that make up the outer surface of the body.

• Cells of epithelial tissue appear in different shapes and structure.

• General functions of epithelial tissue include signal transduction,

protection, secretion, absorption ,excretion, filtration, diffusion and

sensory reception

STEP 7: Evaluation (5 minutes)

• What is an epithelial tissue?

• What are the types of epithelial tissues?

• What are the functions of epithelial tissue?

Step 8: Assignment (10 minutes)

|Activity: Take Home Assignment (10 minutes) |

| |

|DIVIDE learners in groups or individual. |

| |

|ASK the learners to work on the following assignment |

| |

|Explain structure of epithelial tissue |

| |

|ALLOCATE time for learners to do the assignment and submit |

| |

|REFER learners to recommended references |

References

National Cancer Institute. SEER Training Modules. Retrieved

From:http://training.seer.cancer.gov/anatomy/cells_tissues_membranes/tissu

es/epithelial.html . September 2015

Seeley, R. R., Stephens, T. D.& Tate, P. (2003). Anatomy and Physiology.

New York:

McGraw-Hill

Shier, A., Butler, J., & Lewis, R. (2004). Hole’s Human Anatomy &

Physiology. New York:

McGraw-Hill

Standring, S. (2008). Grays’s Anatomy The anatomical basis of clinical

practice. United

Kingdom: Churchill Livingstone Elservier.

Thibodeau, G. A., & Patton, K. T. (1999). Anatomy & Physiology. Saint

Louis: Mosby,

Von Hoffman Press, Inc.

Tortora, G.J & Derrickson, B (2009). Principles of Anatomy and Physiology

12th Edition,

USA, John Wiley & Sons Inc, USA

Waugh, A. & Grant, A. (2006). Ross and Willson Anatomy and physiology in

Health and

illness. United Kingdom: Churchill Livingstone Elservier

← Previous Topic Next Topic →View all Human Anatomy and Physiology topics Open Complete Full Notes

PDF / OFFLINE NOTES

Unataka kutumiwa notes hizi kupitia WhatsApp?Kwa notes zilizopangiliwa vizuri kwa kusoma offline au PDF, bonyeza kitufe hapa chini. Ujumbe wenye Level, Semester, Module na Topic utaandaliwa moja kwa moja.TUMIWA NOTES WHATSAPP

WhatsApp: 255620339260