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4. Tissues. Tissues. Tissue A group of closely associated cells that perform related functions and are similar in structure Epithelial tissue —covering (Ch 4 and 5) Connective tissue —support (Ch 4, 5, 6, and 9) Muscle tissue —movement (Ch 10 and 11)

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4

Tissues

tissues
Tissues
  • Tissue
    • A group of closely associated cells that perform related functions and are similar in structure
  • Epithelial tissue—covering (Ch 4 and 5)
  • Connective tissue—support (Ch 4, 5, 6, and 9)
  • Muscle tissue—movement (Ch 10 and 11)
  • Nervous tissue—control (Ch 12–16 and 25)
epithelial tissue
Epithelial Tissue

Epithelial Tissue

Functions of epithelia

Protection

Diffusion

Absorption, secretion, and ion transport

Filtration

Forms slippery surfaces

  • Covers a body surface or lines a body cavity
  • Forms parts of most glands
special characteristics of epithelia
Special Characteristics of Epithelia
  • Support by connective tissue
  • Avascular butinnervated
    • Epithelia receive nutrients from underlying connective tissue
  • Regeneration
    • Lost cells are quickly replaced by cell division
special characteristics of epithelia1
Special Characteristics of Epithelia

Narrow

extracellular

space

Cilia

Microvilli

Apical region of

an epithelial cell

Cell junctions

Tight junction

Epithelium

Adhesive belt

Desmosome

Gap junction

Basal region

Basal

lamina

Basement

membrane

Reticular

fibers

Nerve ending

Connective

tissue

Capillary

Figure 4.1

classifications of epithelia
Classifications of Epithelia

First name

Last name

describes shape of cells

Squamous—cells are wider than tall (plate-like)

Cuboidal—cells are as wide as tall, like cubes

Columnar—cells are taller than they are wide, like columns

  • indicates number of cell layers
    • Simple—one layer of cells
    • Stratified—more than one layer of cells
classifications of epithelia1
Classifications of Epithelia

Apical surface

Squamous

Basal surface

Simple

Apical surface

Cuboidal

Basal surface

Stratified

(a) Classification based on number

of cell layers

Columnar

(b) Classification based on cell shape

Figure 4.2

simple squamous epithelium
Simple Squamous Epithelium
  • Description—single layer; flat cells with disc-shaped nuclei
  • Function
    • Passage of materials by passive diffusion and filtration
    • Secretes lubricating substances in serosae
  • Location
    • Renal corpuscles
    • Alveoli of lungs
    • Lining of heart, blood, and lymphatic vessels
    • Lining of ventral body cavity (serosae)
simple squamous epithelium1
Simple Squamous Epithelium

(a) Simple squamous epithelium

Description: Single layer of flattened

cells with disc-shaped central nuclei

and sparse cytoplasm; the simplest

of the epithelia.

Air sacs of

lung tissue

Function: Allows passage of materials

by diffusion and filtration in sites where

protection is not important; secretes

lubricating substances in serosae.

Nuclei

of squamous

epithelial

cells

Location: Kidney glomeruli; air sacs

of lungs; lining of heart, blood vessels,

and lymphatic vessels; lining of ventral

body cavity (serosae).

Photomicrograph: Simple squamous epithelium

forming part of the alveolar (air sac) walls (200).

Figure 4.3a

simple cuboidal epithelium
Simple Cuboidal Epithelium
  • Description
    • Single layer of cubelike cells with large, spherical central nuclei
  • Function
    • Secretion and absorption
  • Location
    • Kidney tubules, secretory portions of small glands, ovary surface
simple cuboidal epithelium1
Simple Cuboidal Epithelium

(b) Simple cuboidal epithelium

Description: Single layer of

cubelike cells with large, spherical

central nuclei.

Simple

cuboidal

epithelial

cells

Function: Secretion and absorption.

Basement

membrane

Location: Kidney tubules; ducts

and secretory portions of small

glands; ovary surface.

Connective

tissue

Photomicrograph: Simple cuboidal epithelium

in kidney tubules (430).

Figure 4.3b

simple columnar epithelium
Simple Columnar Epithelium
  • Description—single layer of column-shaped (rectangular) cells with oval nuclei
  • Function
    • Absorption
    • Secretion of:
      • Mucus
      • Enzymes
      • other substances
    • Ciliated type propels mucus or reproductive cells by ciliary action
simple columnar epithelium1
Simple Columnar Epithelium
  • Location
    • Nonciliated form lines:
      • digestive tract
      • gallbladder
      • ducts of some glands
    • Ciliated form
      • Lines small bronchi, uterine tubes, and uterus
simple columnar epithelium2
Simple Columnar Epithelium

(c) Simple columnar epithelium

Description: Single layer of tall cells

with round to oval nuclei; some cells

bear cilia; layer may contain mucus-

secreting unicellular glands (goblet

cells).

Simple

columnar

epithelial

cell

Function: Absorption; secretion of

mucus, enzymes, and other substances;

ciliated type propels mucus (or

reproductive cells) by ciliary action.

Location: Nonciliated type lines most

of the digestive tract (stomach to anal

canal), gallbladder, and excretory ducts

of some glands; ciliated variety lines

small bronchi, uterine tubes, and some

regions of the uterus.

Basement

membrane

Photomicrograph: Simple columnar epithelium

of the stomach mucosa (1150).

Figure 4.3c

pseudostratified columnar epithelium
Pseudostratified Columnar Epithelium
  • Description
    • All cells originate at basement membrane
    • Only tall cells reach the apical surface
    • May contain goblet cells and bear cilia
    • Nuclei lie at varying heights within cells
      • Gives false impression of stratification
pseudostratified columnar epithelium1
Pseudostratified Columnar Epithelium
  • Function—secretion of mucus; propulsion of mucus by cilia
  • Locations
    • Nonciliated type
      • Ducts of male reproductive tubes
      • Ducts of large glands
    • Ciliated variety
      • Lines trachea and most of upper respiratory tract
pseudostratified ciliated columnar epithelium
Pseudostratified Ciliated Columnar Epithelium

(d) Pseudostratified columnar epithelium

Cilia

Description: Single layer of cells of

differing heights, some not reaching

the free surface; nuclei seen at different

levels; may contain mucus-secreting

goblet cells and bear cilia.

Mucus of

goblet cell

Pseudo-

stratified

epithelial

layer

Function: Secretion, particularly of

mucus; propulsion of mucus by ciliary

action.

Location: Nonciliated type in male’s

sperm-carrying ducts and ducts of large

glands; ciliated variety lines the trachea,

most of the upper respiratory tract.

Basement

membrane

Photomicrograph: Pseudostratified ciliated

columnar epithelium lining the human trachea (780).

Trachea

Figure 4.3d

stratified epithelia
Stratified Epithelia
  • Properties
    • Contain two or more layers of cells
    • Regenerate from below (basal layer)
    • Major role is protection
    • Named according to shape of cells at apical layer
stratified squamous epithelium
Stratified Squamous Epithelium
  • Description
    • Many layers of cells are squamous in shape
    • Deeper layers of cells appear cuboidal or columnar
    • Thickest epithelial tissue
      • Adapted for protection from abrasion
stratified squamous epithelium1
Stratified Squamous Epithelium
  • Two types—keratinized and non-keratinized
      • Keratinized
        • Location—epidermis
        • Contains the protective protein keratin
        • Waterproof
        • Surface cells are dead and full of keratin
      • Non-keratinized
        • Forms moist lining of body openings
stratified squamous epithelium2
Stratified Squamous Epithelium
  • Function—Protects underlying tissues in areas subject to abrasion
  • Location
    • Keratinized—forms epidermis
    • Nonkeratinized—forms lining of mucous membranes
      • Esophagus
      • Mouth
      • Anus
      • Vagina
      • Urethra
stratified squamous epithelium3
Stratified Squamous Epithelium

(e) Stratified squamous epithelium

Description: Thick membrane composed

of several cell layers; basal cells are

cuboidal or columnar and metabolically

active; surface cells are flattened

(squamous); in the keratinized type, the

surface cells are full of keratin and dead;

basal cells are active in mitosis and

produce the cells of the more superficial

layers.

Stratified

squamous

epithelium

Nuclei

Function: Protects underlying tissues

in areas subjected to abrasion.

Basement

membrane

Location: Nonkeratinized type forms the

moist linings of the esophagus, mouth,

and vagina; keratinized variety forms the

epidermis of the skin, a dry membrane.

Connective

tissue

Photomicrograph: Stratified squamous epithelium

lining the esophagus (430).

Figure 4.3e

stratified cuboidal epithelium
Stratified Cuboidal Epithelium
  • Description—generally two layers of cube-shaped cells
  • Function—protection
  • Location
    • Forms ducts of:
      • Mammary glands
      • Salivary glands
      • Largest sweat glands
stratified cuboidal epithelium1
Stratified Cuboidal Epithelium

(f) Stratified cuboidal epithelium

Description: Generally two

layers of cubelike cells.

Basement

membrane

Cuboidal

epithelial

cells

Function: Protection

Location: Largest ducts of sweat

glands, mammary glands, and

salivary glands.

Duct

lumen

Photomicrograph: Stratified cuboidal epithelium forming

a salivary gland duct (285).

Figure 4.3f

stratified columnar epithelium
Stratified Columnar Epithelium
  • Description—several layers; basal cells usually cuboidal; superficial cells elongated
  • Function—protection and secretion
  • Location
    • Rare tissue type
    • Found in male urethra and large ducts of some glands
stratified columnar epithelium1
Stratified Columnar Epithelium

(g) Stratified columnar epithelium

Description: Several cell layers;

basal cells usually cuboidal;

superficial cells elongated

and columnar.

Basement

membrane

Function: Protection; secretion.

Stratified

columnar

epithelium

Location: Rare in the body; small

amounts in male urethra and in large

ducts of some glands.

Underlying

connective

tissue

Photomicrograph: Stratified columnar epithelium

lining of the male urethra (315).

Urethra

Figure 4.3g

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