CHAPTER 05 Histology: EPITHELIUM

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CHAPTER 05

ANATOMY & PHYSIOLOGY I BIO 211:

Dr. Lawrence G. Altman www.lawrencegaltman.com Some illustrations are courtesy of McGraw-Hill.












Histology: EPITHELIUM Part 01: Brief Introduction Part 02: Survey of Types

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TISSUES Group of cells closely associated in: a) structure (similar) b) function (common or related)

HISTOLOGY = the study of tissues

TYPES In general, FOUR (4) MAJOR TYPES:

1. EPITHELIAL (this week's topic) 2. CONNECTIVE (supportive) 3. MUSCLE (movement) 4. NERVOUS (control)

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EPITHELIA

LOCATIONS: COVERING or LINING EPITHELIUM of-

a) FREE SURFACES (i.e. SKIN)

b) LINING of OPEN CAVITIES (i.e. DIGESTIVE, RESPIRATORY SYSTEMS)

c) LINING of CLOSED CAVITIES (i.e. VENTRAL BODY CAVITY)

d) LINING of BLOOD VESSELS and HEART May also serve as a GLANDULAR EPITHELIUM To be discussed…

5 EPITHELIA MANY FUNCTIONS

PROTECTION Bacterial Infections, Injury etc

ABSORPTION Example: lining of digestive tract

FILTRATION Example: Renal (renal = kidney)

SECRETION Example: glandular epithelium

…or any COMBINATION of the above.

6 EPITHELIAL FEATURES

TIGHTLY PACKED:Little extracellular space

Surface view ofsimple squamous epithelium

stripped from underlyingconnective tissue

in the peritoneal cavity.

EXISTS as SHEETS:

Cells attached by

tight junction points and

desmosomes (binding bodies).

TIGHT JUNCTION impermeable

OPEN SPACE

CELL 1 CELL 2

DESMOSOME anchoring junction

7 EPITHELIAL FEATURES POLARITY

APICAL surface: often contain MICROVILLI: highly folded EXTENSIONS of the PLASMA MEMBRANE Increases ABSORBTION area Note: “brush border” = many microvilli

MICROVILLI from SMALL INTESTINAL

EPITHELIUM

TEM: 3 Cells shown ^

N N N

BRUSH BORDER

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CILIA

BASAL BODY (centriole) 9 Microtubule triplets

CORE 9 + 2

Microtubule doublets

FLAGELLA: simply longer projections from BASAL BODY;

cell propels itself

(cilia move substances over a surface)


BASAL surface: bottom - most layer of epithelial tissue is always attached to a BASEMENT MEMBRANE.

Acts as a barrier between the EPITHELIUM and the underlying CONNECTIVE TISSUE.

BASEMENT MEMBRANE

EPITHELIUM


BASAL surface: The BASEMENT MEMBRANE is composed of two layers.

Closest to the epithelium Actually secreted by the epithelium.

BASAL LAMINA

- thin, non - cellular adhesive layer -  selective filter of materials from blood - template for wound repair

Below the BASAL LAMINA Extracellular network of collagen fibers

RETICULAR LAMINA BASAL LAMINA + RETICULAR LAMINA = BASEMENT MEMBRANE


SEM: BASEMENT MEMBRANE

EPITHELIAL

CELLS

BASAL

LAMINA

RETICULAR

LAMINA collagen fibers

BM


AVASCULARITY -  No blood vessels

-  Nutrients etc. via DIFFUSION (upward)

- IS innervated

REGENERATION -  High MITOTIC INDEX (turnover)

END of PART 01: Brief Introduction

NEXT: Part 02: Survey of Types

13 EPITHELIA: SURVEY of TYPES

CLASSIFICATION of EPITHELIA

Number of Layers

SIMPLE epithelium: one layer of cells

cells

BM

BM

STRATIFIED epithelium: multiple layers of cells

SHAPE of cells

SQUAMOUS flattened CUBOIDAL height = width COLUMNAR height > width

STRATIFIED EPITHELIUM: layers may have DIFFERENT SHAPES but nomenclature based upon the CELL SHAPE of the free (APICAL) surface.

Number of Layers

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SIMPLE epithelium: Little protection; other functions

EPITHELIA: SURVEY of TYPES


TYPES SIMPLE SQUAMOUS SIMPLE CUBOIDAL SIMPLE COLUMNAR PSEUDOSTRATIFIED PSEUDO = FALSE OR FAKE

In other words, ALL of the shapes May exist in the one cell layer arrangement!

Looks stratified but really NOT!

ONE LAYER of cells but different heights

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PSEUDOSTRATIFIED PSEUDO = FALSE or FAKE

TYPES EPITHELIA: SURVEY of TYPES


SIMPLE SQUAMOUS EPITHELIUM

Types SIMPLE SQUAMOUS SIMPLE CUBOIDAL SIMPLE COLUMNAR

PSEUDOSTRATIFIED PSEUDO = FALSE or FAKE

FLATTENED SINGLE LAYER usually quite permeable

LUNGS: DIFFUSION KIDNEY:

FILTRATION

In certain locations-‐ special names:

ENDOTHELIUM: LINING of BLOOD VESSELS/CAPILLARIES

MESOTHELIUM: SEROSAL MEMBRANES

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Also see:



SIMPLE SQUAMOUS EPITHELIUM

Endothelium

(RBCs in a CAPILLARY)

LAB ATLAS PLATES 9-‐C and 9-‐E

ALVEOLUS (LUNG)

LAB ATLAS PLATE 85-‐D

BOWMAN'S CAPSULE (KIDNEY) LAB ATLAS PLATE 97-‐D

Picture Equivalent

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TYPES: SIMPLE SQUAMOUS SIMPLE CUBOIDAL SIMPLE COLUMNAR

Also see:



DISTAL TUBULE (KIDNEY) Lab Atlas: PLATE 9-‐F

KIDNEY: ABSORPTION (Many MICROVILLI)

usually quite permeable

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NO CILIA

EXAMPLE: DIGESTIVE TRACT (STOMACH to ANUS)

CILIATED

EXAMPLE: UTERINE TUBES

BOTH TYPES: GOBLET CELLS

MAY BE PRESENT (MUCOUS PRODUCTION)

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SIMPLE epithelium:

Little protection; other functions

SIMPLE SIMPLE SIMPLE



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SIMPLE epithelium Little protection; other functions



SIMPLE COLUMNAR EPITHELIUM

cilia

non-‐ciliated (mucous -‐ producing)

OVIDUCT PANCREATIC DUCT PHOTO EQUIVALENT: 10a

also in STOMACH

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MAY HAVE CILIA EXAMPLE: RESPIRATORY TRACT

REALLY SIMPLE EPITHELIUM !!!!

why??? -‐ALL CELLS REST ON BM -‐SOME DO NOT REACH

APICAL SERVICE -‐NUCLEI AT DIFFERENT

LEVELS GIVING FALSE APPEARANCE of BEING STRATIFIED

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MONKEY TRACHEA

PICTURE EQUIVALENT: LAB ATLAS: Human Trachea

PLATE 10-‐B

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PSEUDOSTRATIFIED COLUMNAR EPITHELIUM (ciliated)

SEM of CILIA in TRACHEA

CILIA

GOBLET CELLS

24 STRATIFIED SQUAMOUS EPITHELIUM

MOST COMMON TYPE Of STRATIFIED EPITHELIUM

-‐PROTECTION vs. ABRASION -‐HIGH MITOTIC INDEX

-‐CELLS SHED FROM APICAL REGION

STRATIFIED epithelium: Different layers may have

different shapes BUT

nomenclature:

BASED ON CELL SHAPE of the

free (APICAL) surface

BASAL LAYERS: -‐USUALLY NOT SQUAMOUS

-‐SITE OF NEW CELL GENERATION

APICAL SURFACE MAY POSSESS KERATIN, A

WATER INSOLUBLE PROTEIN

25 STRATIFIED SQUAMOUS EPITHELIUM

HUMAN SKIN (keratinized) PICTURE EQIVALENT:

Lab Atlas: Fig. 11-‐A

ORAL CAVITY

PICTURE EQUIVALENT: Atlas: Fig. 10-‐D

Keratinized Cells

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REMINDER: STRATIFIED EPITHELIUM NAMED ON BASIS of

APICAL LAYER

STRATIFIED COLUMNAR EPITHELIUM

VERY RARE! -‐URETHRA of MALE

-‐some LARGE DUCTS of GLANDS

27 STRATIFIED CUBOIDAL EPITHELIUM

ALSO VERY RARE!

-‐2 to 3 CELLS DEEP

-‐ LARGEST DUCTS of: SWEAT GLANDS

MAMMARY GLANDS

SALIVARY GLANDS

SURROUNDING EGGS

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RELAXED DISTENDED

CUBOIDAL

COLUMNAR

“UMBRELLA CELLS”

TRANSITIONAL EPITHELIUM

THINK URINARY BLADDER !

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Bladder


PICTURE EQUIVALENT: ATLAS:

Fig. 11-‐B (RELAXED) Fig. 11-‐C (DISTENDED)

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LAST SLIDE


CHAPTER 05 Histology: EPITHELIUM

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