G.Histology

General Histology

Histos+logus= Histology (Science of tissues). - A cell is the basic unit of an organism. - A group of cells whether similar or different cells) may form a tissue. - A group of tissues may form an organ. A group of organs will establish a living organism (multicellular animals). Tissue: is groups of cells closely associated that have a similar structure and perform a related function
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Classification of cells

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).
Prokaryotic cell(prokaryote)
A unicellular organism that lacks a membrane-bound nucleus (karyon), mitochondria, or any other membrane-bound organelle. The word prokaryote comes from the Greek (pro) "before" and κάρυον (karyon) "nut or kernel”.2 domains, archaea and bacteria Ayoub Bazzaz, (BSc,MSc,PhD,DPSI)

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

EukaryoticAmoeba, Muscle cell

Comparison of eukaryotes vs. prokaryotes

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Cell division

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Cell division

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Tissue culture

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Key Terms

Histology: the study of tissues. Tissues: Simply groups of similar cells that work together performing the same task Greatest form of teamwork in the body

Why Study Histology?

Knowing the difference between normal and abnormal tissue is the first step in diagnosis and treatment of patients.

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Tissues
Four types of tissue Epithelial = covering Connective = support Muscle = movement Nervous = control Most organs contain all 4 types Connective tissue has non-living extra-cellular material [ECM] or (matrix) between its cells

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

4 Types of Tissue
. Epithelium . Connective . Muscle . Nervous

Skin, our largest organ

* made of all four tissue types

Epithelial Tissue

Makes up 3% of your body weightThey don’t moveThey don’t send messagesTheir cells are all touching one anotherOf all tissues, they are the most widely varied in structure and function.All sit on a basement membrane.

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Epithelial Tissues
Sheets of cells Specialized contacts/cell junctions (see below) Basal lamina: protein scaffolding secreted by epithelial cells Basement membrane: reticular fibers (crossed collagen network) that supports epithelium--really associated connective tissue Connective tissue support Nutrients from capillaries in underlying connective tissue Nerves pass through Easily regenerates E.g. skin, lining of gut, mucous membranes

Locations of Epithelial Tissues

Covers the body (epidermis) Found on the inside of hollow organs and the outside of all organs Found above a connective tissue layer (epi = above) Lines the cavities, tubes, ducts, and blood vessels inside the body.


Epithelial Anatomy
Apical surface – upper surface, is free or exposed to the “exterior”Basal surface – attached surface (below)Microvilli – small fingerlike extensions that increase the surface area allowing for more work to be done

Functions of Epithelial Tissue

Protects from physical & chemical injury Protects against microbial infection Contains nerve endings which respond to stimuli. Filters, secretes & reabsorbs materials Secretes fluids to lubricate joints

Cell Organization

Simple – single layer of cells; typically found where absorption and filtration occur or a single layer of epithelial is neededsimple squamoussimple cuboidal simple columnarStratified – layers of cells; common in areas where protection is needed like the skinstratified squamousstratified cuboidalstratified columnar

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Simple: just one layer or cell shape
Stratified: multiple layers and cell shapes
Classes of Epithelia

Epithelial Tissue in Review…

Three Basic Shapes
Squamous – like scales, or pancakes (“being squashed like a pancake”)Cuboidal – looks like cubesColumnar – longer and look like columns

Two Types of Stratified Columnar

Ciliated


Unciliated
cilia
No cilia

Squamous Epithelium

Simple – one cell thick Forms solid layer of cells which line blood vessels, body cavities and covers organs in body cavities
Stratified – multiple layersForms epidermis

Cuboidal Epithelium

Simple – one cell thickRoughly cube shaped Line ducts in kidneys where re-absorption and secretion activities take place.
Duct
Cuboid Cells
Duct
Cuboid Cells

Columnar Epithelium

Simple – one cell thickColumn shaped (long and narrow)Lines digestive tract where re-absorption & secretion occurs.

Confusing Epithelial Tissue

Transitional Epithelium – stratified tissue that can’t make up its mind as to whether it is squamous or cuboidalShape of cells depends upon the amount of stretching (urinary bladder)


Confusing Epithelial Tissue Continued… “Pseudostratified Columnar Epithelium”Looks like it has more than one layer because of the position of the nucleusNuclei are positioned at differing levelsCells narrow in the area without nucleus

Types of Epithelial Membranes

Mucous or mucosa– lining of tubes; moistens and protects from enzymes (stomach, trachea, and vagina)Serous or serosa – outside of organs; lubricates (all thoracic, abdominal and pelvic organs)Cutaneous or skin – body surface; protection Synovial – synovial joints; lines and protects synovial cavities (elbow, knee, hip, etc.)

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Stratified Epithelia
Squamous E.g. epidermis
Transitional epithelium E.g. urinary structures--bladder Stretches from 6 cells to 3 cells thick as bladder fills and expands

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Can You Identify the Classes of Epithelium?
A
B
C
D
E
Quiz!!



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Tight junctions: impermeable e.g. gut tube, doesn’t let enzymes from gut into blood stream.
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Cell Junctions
Desmosome: binding spots between cells with proteins called cadherins

Desmosomes

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Gap junctions

Are tubes that let small molecules pass between cells. Are a specialized intercellular connection between a multitude of animal cell-types. Directly connect the cytoplasm of adjacent cells, which allows various molecules, ions and electrical impulses to directly pass through a regulated gate between cells.
Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Features of Lateral Surface of Epithelium
Cells are connected to neighboring cells via: Proteins-link cells together, interdigitate Contour of cells-wavy contour fits together Cell Junctions Desmosomes-adhesive spots on lateral sides Tight Junctions-at apical area, plasma membrane of adjacent cells fuse, nothing passes Gap junction-spot-like junction occurring anywhere, lets small molecules pass

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Features of Apical Surface of Epithelium
Microvilli: In small intestine Finger-like extensions of the plasma membrane of apical epithelial cell Increase surface area for absorption Cilia: Respiratory tubes Whip-like, motile extensions Moves mucus, etc. over epithelial surface 1-way Flagella: spermatoza Extra long cilia Moves cell

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Features of the Basal Surface of Epithelium
Basal lamina: supportive sheet between epithelium and underlying connective tissue Selective filter Basement membrane = basal lamina plus underlying reticular fiber layer Attaches epithelium to connective tissue below Sometimes the two are used interchangeably



Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).
Name that Epithelial Feature!(name and location on cell)
Cilia Tight junction Microvilli Basement membrane
2
3
4
1
3 1 2 4

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Glands: epithelial cells that make and secrete a water-based substance
Exocrine Glands Secrete substance onto body surface or into body cavity Have ducts E.G., salivary, mammary, pancreas, liver
Endocrine Glands Secrete product into blood stream Either stored in secretory cells or in follicle surrounded by secretory cells Hormones travel to target organ to increase response No ducts

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).