Histology

Four Types of basic tissue

1. Epithelial

2. Connective

3. Muscular

4. Nervous

Epithelial tissue

sheets of cells covering body surfaces and lining cavities

Function of epithelial cells

protection, secretion, absorption, and filtration

endothelium

inner lining of blood vessels and lymph vessels

mesothelium

lines abdomen, heart and pleural cavities

characteristics of epithelium and what they mean

1. cellularity- how many layers (simple or stratified)

2. polarity- has two domains (apical- top and basal-bottom, and lateral- side domain)

3. avascularity: no direct blood supply

4. high mitotic rate- high turnover and regeneration

pseudo-stratified epithelium

single layer of epithelium with all cells attached to the basement membrane , and the orientation appears to have it layers

squamous epithelial cells

flat and thin cells that facilitate diffusion and filtration.

cuboidal epithelium

they are as wide as they are long and are involved in secretion and absorption.

columnar epithelium

they are longer than they are wide and are primarily involved in absorption, secretion, and protection.

what are the special surface modifications that epithelial cells can have

1. cilia

2. microvilli

3. stereocilia

Cilia

motile, hair like fibers- these can move materials and are found in places like the respiratory tract and the fallopian tubes

microvilli

nonmotile hair like structures, shorter hairs- these can be found in the small intestine and the kidneys

stereocilia

these are loner hairs that are nonmotile, and can be found in the the epididymus and the inner ear

list the junctional complexes in epithelial cells

1. tight junctions

2. adhering junctions

3. desmosomes

4. hemidesmosomes

5. gap junctions

tight junctions

these prevent all material from passing through- this is when we don’t want material to infiltrate cells

• cells touch at these junctions, almost like a buttoned up shirt that doesn’t fit someone

adhering junctions

These junctions have firm cell adhesion, and resist tensile forces

desmosomes

resist against shear forces

hemidesmosomes

allows for attachment to the basement membrane

gap junctions

allows molecules to diffuse, and cell communication- good for nutrition purposes since these tissues are avascular

Where can you find simple squamous epithelium?

2 types

1. endothelium: lines the heart and blood vessels

2. mesothelium- lines the abdomen, pleural and heart chambers

Where can you find simple cuboidal epithelium?

these can be found in small ducts, and kidney tubules

where can you find simple columnar epithelium?

digestive tract and uterine tubes

what are the two kinds of stratified squamous epithelium?

keratinized and nonkeratinized

where can you find keratinized stratified squamous epithelium?

skin

Where can you find nonkeratinized stratified squamous epithelium?

mouth, esophagus, vagina, anal canal

where can you find stratified cuboidal and columnar cells?

these are rare but can be found in some ducts and glands

where can you find pseudostratified epithelium?

you can find this in the respiratory tract, vas deferns, and epididymis

where can you find psuedostratified epithelium that has cilia on it?

trachea and bronchi

where can you find pseudostratified epithelium with stereocilia on it?

epididymis and vas deferens

what are glands?

they are composed of epithelial tissue, and they develop from epithelial cells that are specialized in secretion

what are the types of glands?

exocrine and endocrine

Exocrine glands

these are connected to the surface via ducts and secrete onto surfaces or into lumens

endocrine glands

these secrete directly into the blood stream or interstitial fluid (no ducts)- they use the capillaries

what are the ways to classify exocrine glands?

1. secretory product

2. mechanism of secretion

3. cell number

4. morphology

Serous glands- what they secrete and examples

they secrete a watery, protein/enzyme rich secretion

• ex. parotid gland, pancreas and sweat glands

Mucous glands- what they secrete and examples?

they secrete viscous mucus (glycoprotein and water), which provides some level of lubrication- this is a very thick material

• examples: goblet cells, respiratory and stomach epithelium

Mixed “seromucous” glands- what do they secrete and examples

-they secrete a mixture of both the serous (watery, protein/enzyme rich substance) and mucus (glycoprotein and water)

• examples: submandibular, sublingual, and tracheal glands

Sebaceous glands- what do they secrete and where are they located?

these secrete a lipid/ sebum secretion

• example: skin sebaceous glands

What are the mechanisms of secretion?

1. Merocrine

2. Apocrine

3. Holocrine

merocrine secretion

this deals with no release of cytoplasm

• this can be found in the pancreatic acinar cells, and the salivary glands

apocrine secretion

this deals with some loss of cytoplasm from the apical surface of the epithelial cells

• these can be found in the mammary glands

holocrine secretion

this is where the entire cells dissolves/ gets released with secretion

• ex. the sebaceous glands

what are the classifications by cell number for exocrine glands

1. unicellular

   • single secretory cell performing the secretion

   • ex. goblet cells in the intestines and the respiratory tract

2. multicellular

   • formed into ducts and units

   • there is a secretory portion (end piece) and the excretory duct

   • there are a bunch of subtyoes based on morphology

what are the types of morphology classification of the ducts?

1. simple glands (unbranched or uncoiled)

2. compound glands (branched)

   • tubular

   • acinar

   • tubuloacinar

where can you find a simple tubular gland?

these can be found in the small and large intestine

What type of gland is this?

simple tubular and it can be found in the large and small intestines

What kind of gland is this?

this is a simple branched tubular gland, and you can find this in the stomach and the uterus

What kind of gland is this?

simple coiled tubular gland and it can be found in the sweat glands

What kind of gland is this and where is it located?

this is a simple acinar gland and can be found in the urethra

What kind of gland is this and where can you find it?

Simple branched acinar glands, and this can be found in the sebaceous glands of the skin

What are the compound gland morphologies?

1. compound tubular

2. compound acinar

3. compound tubuloacinar

what kind of gland is this and where can you find it?

compound tubular gland and you can find it in the glands of the duodenum

what kind of gland is this and where can you find it?

compound acinar gland and you can find it in the lacrimal glands, pancreas, and mammary glands

what kind of gland is this and where can you find it?

compound tubuloacinar gland and these can be located in the submandibular and sublingual glands

what is the hierarchy of ducts

secretory units to intercalated ducts (small intralobular) into striated ducts (larger intralobular) into interlobular ducts (in connective tissue septa) into lobar ducts and then the main excretory duct

characteristics of the endocrine glands

there are mo ducts and it has a high vascularity, the secretory cells are surrounded by capillaries, and the hormones are released directly into the bloodstream

major endocrine glands

pituitary, thyroid, parathyroid, adrenal glands

functions of the endocrine glands

synthesize store and secrete hormones into circulation