Histology 2

7/31/2019 Histology 2

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Introduction to Histology Vertebrate Organization:molecules

organelles

cells

tissues

organs

organ systemsorganism

All the different cells in the body originate from a single cell.

cartilage neurons muscle

gut lining

TISSUES

groups of related cells with

similar function

Histology = study of tissues

Related cells (tissues) have similar biochemical make-up.

3 steps:

(1) Fixation

(2) Sectioning(3) Staining

H&E stainingnuclei = purple

cytoplasm, matrix proteins = pinkish

Tissue stained to

indicate insulin

BIO223: Human Anatomy L02: Epithelium UNC-Asheville, f2011


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Slides give you a 2D look at a 3D structure.Structures look different depending on how/where they are sliced.

Longitudinal

(LS)

Cross-section

Sections:

(XS)

Oblique section

EPITHELIUM

CONNECTIVE TISSUE

MUSCLE

NERVOUS TISSUE

4 basic kinds of tissues make up all structures in body:

EPITHELIUM

CONNECTIVE TISSUE

MUSCLE

NERVOUS TISSUE

4 basic kinds of tissues make up all structures in body: Covers surfaces

Apical Surface (free edge)

Basal lamina (= Basement Membrane) attaches epithelium to the

underlying tissues

Cells have polarity

Cells packed closely together

Characteristics of Epithelium:

o en speca ze unc ons e ween ce s

little ECF = Extra-Cellular Fluid [aka interstitial fluid(ISF)]

High rate ofmitosis and regeneration

Avascular contains no blood vessels

all nutrients and oxygen must diffuse from the underlying tissue

[blood vessels themselves are a special case endothelium]



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Vertebrates have tube-within-a-tube body plan

Different tissue types arise from different layers of the embryo

Epithelium covers all surfaces that open to the outside of body

mouthEarly embryo

Lancet

anus

free space filled with air or fluid

nucleus

single cell

Apical Surface

EpitheliumEpitheliumEpitheliumEpithelium

Basal

Lamina

Connective TissueConnective Tissue

Polarity

Organelles are notdistributed

evenly throughout cytoplasm

there is a top (apical) and

bottom (basal)

Apicalsurface (top)

Basallamina (bottom)

Cell-1 Cell-2

Apical surface(microvilli)

Specialized junctions

connect tightly-packed cells, and

regulate communication among

neighboring cells

Basal lamina

attaches epithelium to underlying

Basal lamina

connective tissue.

Functions of epithelium:

All contact w/ external world mediated by epithelium

Protection

Control permeability, absorption & secretion

Sensation (neuroepithelium)

(e.g. sweat, synovial fluid, hormones, milk, digestive enzymes)

2. Cuboidal

3. Columnar

SHAPE:(as seen in cross-section)

Classification of epithelial tissues:

1. SquamousBasal lamina

StratifiedSimple Pseudostratified



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Classification is based on # of layers and

shape of cells at apical surfaceExamples

Simple

epithelium

lines body cavity (coelom)

inside blood vessels/heart

alveoli of lungs

Simple squamous epithelium

~3D cartoonLung alveoli

capillaryEndothelial cell

lumen

Endothelial cell

(simple squamous)

RBCs in

lumen of capillary

Examples

stratified

s uamousepithelium

Examples

Simple

cuboidal

epithelium



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LOCATION: lining of stomach, intestine, gall-

bladder, uterine tubes, collecting ducts of kidneyFUNCTION: protection, secretion, absorption

Examples

Simple

columnar

epithelium

Examples

Stratified

columnar

epithelium

Salivary gland duct

Stratified squamous epithelium (cornea)Stratified squamous epithelium

(wall of vagina)

Simple cuboidal epithelium

(kidney duct, LS)

Simple cuboidal epithelium

(kidney ducts, XS)



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Simple Columnar

epithelium

Stratified cuboidal epithelium

(lactiferous duct of breast)

Pseudo-stratified (columnar) epithelium [special case]

nuclei are at different positions, so it appears layered, but

all the cells contact the basement membrane

Mucosa of trachea

True stratified columnar epithelium

distinct rows of nuclei

Tongue,Mucousgland duct

Pesudostratified epithelium

more irregular arrangement of nuclei

Trachea

Epithelium always has a free surface,

and is named by number of layers

and shape of cells at apical surface.

Epithelium, review

Tissue that covers surfaces

Classified based on cell

shape and number

most epithelial tissues are in

membranes and/or glands



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Epithelium in the body is commonly part of

membranes and glands

Epithelial Membranes

Cutaneous membrane

skin; outer covering of body

Mucous membranes (mucosa)

epithelial lining of wet internal surfaces that connect

to outside of body

Serous membranes (serosa)

epithelial linings inside the body cavity, does notopen

to outside of body

Endothelium

inner lining of blood vessels

Cutaneous membranecovers outside of body

Serous membrane

Does not open to outside

lines body cavity & covers outer

Mucous membrane

Surfaces ultimately connect

to outside of body

sur ace o a omna organs

Glandular Epithelium (secretion)

ENDOCRINE glands

secrete products directly into interstitial fluid (ISF)

and/or bloodstream (e.g. Hormones)

EXOCRINE glands

secrete products through ducts to surface of body

(ex. sweat, digestive enzymes, milk)

Endocrine glands

empty into blood or ECF

Products are called

hormones.

Exocrine glands

empty onto surfaces through ducts

surfaces may be external (skin) or internal (lumen of stomach)



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REVIEW:

Identify the epithelium

shown on each of the

following slides

Indicate the apical surface

and the basal lamina.


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Histology 2