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Epithelium

Four primary tissue types:

• Epithelial (covering)

• Connective (support)

• Nervous (control)

• Muscular (movement)• Smooth muscle• Cardiac muscle• Skeletal muscle

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Epithelial Tissue Features• Epithelial tissues always have an apical and

basal surface.• Avascular with no direct blood supply;

nutrients must diffuse.• Epithelial tissues have a high capacity for

regeneration.

• Cells are in close contact with each other with little or no intercellular space between them.

• May have junctions for both attachment and communication.

• Always resting on a basement membrane

Classified based on:

• Number of layers:• 1 layer = simple• 1 layer irregularly shaped=

pseudostratified• >1 layer = stratified• >1 layer of similar cells =

transitional

• Shape of the cells of outermost layer:• Flat: Squamous• Square, round, cubical: Cuboidal• Tall: Columnar

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Simple Squamous EpitheliumThin single cell layer attached to a basement membrane

Simple squamous: with flattened nuclei. Present in the alveoli of lungs,

Kidneys, Lining of visceral organs and all blood vessels.

Function: selective diffusion, filtration absorption or secretion.

Mesothelium: simple squamous that

lines body cavities and cover organs.

Endothelium: simple squamous that

lines the inside of blood vessels and

capillaries.

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Simple Cuboidal EpitheliumSimple cuboidal: with central rounded nuclei.

Present in liver, pancreas, acini of glands, lines

small ducts and tubules of kidney. Function:

excretory, secretory or absorptive.

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Simple Columnar EpitheliumSimple columnar: with basal oval nuclei.

Present in the absorptive surfaces (intestine);

secretory surfaces (stomach); lining gall bladder

(absorbs water).

Simple Columnar Epithelium (cont’d)

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Pseudostratified Columnar Epithelium

Function: to trap and remove unwanted

particles from the respiratory tract

Pseudostratified

columnar

ciliated: nuclei

disposed at

different levels;

basal cells do not

extend to surface;

Present in larger

airways of

respiratory system

(trachea, bronchi).

Transitional Epithelium

Function:

distension- supplying

elasticity/tension to

urinary bladder

Transitional: urinary tract; accommodates stretching

and toxicity of urine; surface cells larger, pale-staining,

scalloped surface outline; luminal surface appears

thickened; may be binucleate; large, round, prominent

nucleoli.

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Transitional Epithelium (cont’d)

Stratified epithelium = more than 1 layer

Function: protection

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Stratified Squamous nonkeratinized (SSNK)

Function: protection

Stratified squamous non-keratinizing (mucous

membrane): resists abrasion; moistened by glandular

secretions. Present in oral cavity, pharynx, esophagus,

anal canal, uterine cervix, and vagina.

Stratified Squamous keratinized (SSK)

Function: protection

Stratified squamous keratinizing: Upper

cell layer composed of squamous cells.

Present in surface of skin

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Concept Check

The type of epithelium indicated by the arrow lines the:

a) skin

b) mucosa of the esophagus

c) respiratory tract

d) urinary tract

f) mesentery

The type of epithelium shown in this image is:

a) Simple cuboidal

b) Simple columnar

c) Stratified columnar

d) Pseudostratified

columnar (respiratory)

e) Transitional

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GLANDULAR EDPITHELIUM

Glandular Epithelium

Two Main Types of Glandular Tissues:

• Exocrine – release secretions through ducts

• Endocrine - release secretions directly to the blood (covered in subsequent lectures)

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Glandular Epithelium structure

• Glands are classified structurally based on the duct and the secretory portions.

• Ducts considered compound when they are branched and are simple when they are not branched.

• shapes of the secretory portions of glands:• tubular, acinar (rounded), or

• tubulo-acinar (rounded with tubular end)

• branched tubular or coiled tubular (long and not branched)

Nature of secretions

• Serous secretion: secret watery fluid rich in protein (parotid glands)

• Mucous secretion: secret mucus; poor in protein (goblet cells)

• Muco-serus secretion: as in mixed salivary glands

• Milky secretion: mammary gland

• Wax secretion: glands in external ear

• Fatty secretion: sebaceous glands

• Watery secretion: sweat glands

• Cellular secretion: ovary and testis.

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Apocrine glands: a small portion of the apical

cytoplasm discharged with the secretory products.

e.g.. Mammary glands and some sweat glands.

Holocrine glands: discharge whole cell;

sebaceous glands (sebum).

Merocrine glands: in which secretion occurs by

exocytosis; i.e. no cellular changes as parotid

glands.

Modes of Secretions

Simple Tubular Gland

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Simple Branched Tubular Gland

Simple Coiled Tubular Gland

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Compound Acinar Gland

Compound Tubuloacinar Gland

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Mucous cells produce mucus, which doesn't stain very darkly, so the mucous cells look almost clear on these images and on slides. Serous cells produce a watery secretion that contains a lot of proteins and enzymes. Serous cells stain fairly dark.

Endocrine Gland

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Epithelium Summary Tables

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Connective Tissue

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Connective Tissue’s Functions

• Binding and Support• Protection• Mineral storage• Insulation• Energy Storage• Transportation (blood)• Immunity• connective tissues (CT) consist of material between

or outside of cells, largely fibers and a gel-like ground substance.

C.T. Structure• Cells are widely separated among the masses of

fibers and ground substances.

• Fibers and ground substance are termed the extracellular matrix (ECM).

• Fibers, composed of collagen or elastin, are responsible for the tensile strength and elasticity of the tissue.

• Ground substance, composed of hydrated proteoglycans, provides the medium through which dissolved substances pass from capillaries to cells and back.

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Connective Tissue is composed of:

• Cells

• Extracellular Matrix (material outside of cells)

Extracellular matrix, ECM, is composed of fibers of protein and ground substance

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Ground substance consists of glycosaminoglycans and glycoproteins

Cells of the CT

• Mitotically active = “blasts”

• Mature cells = “cytes”

• Fibroblasts = cell that synthesizes the extracellular matrix and collagen

• Mast Cells = histamine release

• Plasma Cells = antibody release

• Adipocytes

• Leukocytes

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Different Cell Types found in C.T.

Connective Tissue Types1) Loose Connective Tissue = loose arrangement of

cells; not very organizedAreolar

Adipose

Reticular

2) Dense Connective Tissue = Tightly packed cells; more organized

Dense Regular

Dense Irregular

Elastic

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Areolar Loose Connective Tissue

Loose Connective Tissue

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Loose Areolar C.T.

• Found in the

lamina propria;

in between muscles,

in lungs.

•Acts as space filler

Loose Reticular C.T.

• Loose arrangement of Reticular fibers: Makes the framework for lymphatic organs i.e. (tonsils, thymus, spleen, lymph nodes)

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Adipose Tissue

Dense Elastic CTFound in arteries, e.g. (aorta)

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Dense Irregular Connective TissueFound in Dermis, pericardium of heart, synovial joint capsule

Dense Regular Connective TissueFound in Tendons & Ligaments

Tendons: attach bone to muscle, Ligaments: attach bone to bone

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Dense Regular Connective Tissue(cont’d)

Dense Regular Connective Tissue(cont’d)

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Quiz # 2 next week 09/17 on this lecture &Assignment #1 due to be handed in at the BEGINNING of class

Assignment #1

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1. Identify the basic tissue indicated by the arrow

Answer

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2. Identify the type of epithelium indicated by the arrow

Answer

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3. Identify the type of epithelium & the cell type indicated by the arrow

Answer

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4. Identify the type of epithelium indicated by the arrowsAnswer

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5.Identify the type of epithelium & name the apical structure (i.e. cilia or microvilli)

Answer

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6. Identify the 2 different cell types in this submandibular gland:-Indicated by the wide and thin arrows

Answer

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7. Identify the type of epithelium and where it is found

Answer

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8. Identify the type of Epithelium and where it is found

Answer

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9. Identify the type of Epithelium & where it is found

Answer

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10. Classify the type of connective tissue

Answer

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11. Classify the type of connective tissue & identify the cell types indicated by the arrow

Answer

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12. Classify the type of connective tissue and the type of fiber stained black

Answer

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13. Classify the type of connective tissue and the type of fiber stained black

Answer

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14. Classify the type of connective tissueAnswer

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15. Classify the type of connective tissueAnswer

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16. Classify the type of connective tissueAnswer

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17. Classify the type of connective tissue

Answer

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18. Classify the type of glandular epithelium

Answer

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19. Classify the type of glandular epithelium

Answer

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20. Classify the type of glandular epitheliumAnswer

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