Human Anatomy, Larry M. Frolich, Ph.D. Epithelial and Connective Tissues Classes of Tissues –Two classes—epithelial, connective –Muscle and Nervous Tissue

Human Anatomy, Larry M. Frolich, Ph.D.

Epithelial and Connective Tissues

• Classes of Tissues– Two classes—epithelial, connective– Muscle and Nervous Tissue (don’t fit in classes)

• Epithelial tissues– General characteristics– Cell shapes

• Connective Tissues– General characteristics (areolar)– Types of connective tissues


General Types of Tissues

•Broad Classes of Tissues-Epithelial: sheet of cells.-Connective: cells in a matrix

•More specific tissue types-do not fit as epithelial or connective-will treat in section two of course-Nervous: carries messages in body-Muscle: effects movement

•Virtually all organs will have all four types

Tissue: a group of closely associated cells that have a similar structure and perform a related function


• Cells connect, on their lateral surfaces, forming sheets– Gap junctions– Tight junctions– desmosomes

• Cells can have appendages, on their apical surface, to interact with environment– Cilia– Microvili– Flagella

• Cells sit, on their basal surface, on a thin basal membrane of collagen fibers for support– Underlying connective tissue further supports

epithelium– Blood vessels/nerves travel in underlying connective

tissue, nerve endings on epithelium

Epithelial Tissues

Examples of epithelium: epidermis, lining of gut, mucous membranes, lining of celom, glands


Appendages on apical surface• Microvilli: (ex) in small intestine

– Finger-like extensions of the plasma membrane of apical epithelial cell

– Increase surface area for absorption• Cilia: (ex) respiratory tubes

– Whip-like, motile extensions– Moves mucus, etc. over epithelial surface 1-

way• Flagella: (ex) spermatoza

– Extra long cilia– Moves cell

Cilia in tracheaa


Connections between

epithelial cells• Desmosome:

binding spots between cells with proteins called cadherins

• Tight junctions: impermeable– E.g. gut tube, doesn’t

let enzymes from gut into blood stream

• Gap junctions: tubes that let small molecules pass between cells


Name that Epithelial Feature!

(name and location on cell)

• Cilia• Tight

junction• Microvilli• Basement

membrane

2

3

4

1

3

1

2

4


• Simple: just one layer or cell shape

• Stratified: multiple layers and cell shapes

Classes of Epithelia


Simple EpitheliaType Cell shape Example

Squamous Squashed Endothelium (lines bloodvessels), mesothelium(serous lining of ce lom)

Cuboidal Cubed Walls of glands

Columnar Columns Lining of gut tube;sometimes with cilia likelining of uterine tube

Pseudo-stratified Flat ce lls give riseto columns

With cilia in respiratorytubes to movemucous/particles out oflungs

Simple squamous epithelium from alveolus of lung


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



Can You Identify the Classes of Epithelium?

A B

C

D

EQuiz!!


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


CONNECTIVE TISSUES

• “Areolar tissue” as model• Universal in body• Underlies epithelium, supports

capillaries, small nn.• Always originates from

mesenchyme• CELLS in MATRIX


Extracellular matrix

• Fibers– Collagen gives structure– Reticular fibers (crossed collagen)

gives order– Elastin gives elasticity

• Ground substance– Jelly-like material made of sugar-

protein molecules (proteoglycans)


Cells of Connective Tissues

• Fibroblasts make fibers• Immune cells in areolar tissue

– Macrophages– Plasma cells– Mast cells– Neutrophils, Lymphocytes



Areolar connective tissue


“Loose” connective tissues

• Adipose tissue mostly under skin and in mesenteries

• Reticular: organized 3-D network of fibers that support lots of cells– E.g. marrow, spleen, lymph nodes



“Dense” Connective tissues

• Irregular– Thick fibers running in many planes– E.g. dermis, fibrous capsules around organs

• Regular– Aligned parallel fibers– Resists tension– E.g. tendon, ligaments, aponeuroses– Sometimes with elastic fibers (e.g.

ligamentum nuchae)



Other Connective Tissues

• Bone• Cartilage• Blood

Documents

Human Anatomy, Larry M. Frolich, Ph.D. Epithelial and Connective Tissues Classes of Tissues –Two classes—epithelial, connective –Muscle and Nervous Tissue