Simple Epithelium and their Pathologies (histology)

simple squamous

apical surface is smooth

width greater than height

flattened nucleus

rest on the basement membrane

ex: cornea and blood vessels (endothelium), air sacs of lungs

simple cuboidal

apical surfaces may have brush borders

width is equal to height is equal to depth

central and spherical nucleus

rest on the basement membrane

ex: kidneys

simple columnar

apical surface may have brush border

height is greater than width

elongated ovoid nucleus on the basal region of the cell

rest on the basement membrane

ex: digestive tract and fallopian tubes

pseudostratified columnar

appears layered but is actually only one layer on the basement membrane

nonuniform cells

columnar and basal cells

usually ciliated

ex: respiratory tract

keratin

dead cells on the epithelium with no nucleus (not always on top of alive cells)

junctions

epithelial cells rest on the basement membrane to which they are anchored via __________ called hemidesmosomes

cilia

elongated, motile structures that transport material

microvilli

smaller than cilia, composed of actin filaments, help with absorption

sterocilia

long microcilia, also made of actin filaments

functions of the epithelium

-protects the body from injury

-absorption of material

-transportation of material along a surface

-secretion of mucus, hormones, and proteins

-gas exchange (in lungs)

-lubrication between surfaces

classify epithelial tissue by

-their number of layers

-their shape (the name of the superficial layer/transitional)

epithelium

type of body tissue that covers all internal an external surfaces of the body, lines the body cavities and hollow organs and is the major tissue in glands

-continuously removed by mitosis

avascu

apical domain

free surface that is exposed to the luminal fluid

may have projections

lateral domain

orients perpendicularly to the apical and basal membranes and is frequently referred to

types of junctions

1. tight

2. adherens

3. desmosomes

4. gap

5. hemidesmosomes

basal domain

attached to an extracellular matrix that supports the epithelial tissue mesothelium

mesothelium

epithelial layer of serous membranes that lines the body cavities and covers the organs that project into the cavities

simple squamous epithelial tissue

2 layers- parietal and visceral (cover different things)

parietal layer of mesothelium

face the cavities of the body

serosal/visceral layer of mesothelium

covers the organs

function of mesothelium

lubrication- prevents organs from touching, protects organs

mesothelial cells

-flattened

-pentagonal shape

-form irregular borders with one another

-basically simple squamous

effusion

excessive fluid in a mesothelial lined cavity

in lungs- pleural ______

in perricardium (heart)- pericardisis

in the peritoneum (digestive tract)- peritonitis

mesothelioma

cancer of the mesothelium (like a tumor)

ex: in lungs, testes, heart, abdomen linings

characteristics of cancer cells

long, slender, and curved microvilli

may invade nearby tissues and organs

endothelium

simple squamous epithelium lining the lumen surface of all types of blood vessels and lymphatic vessels (also called vascular __________)

plays a role in the circulatory system

endothelial cells

flattened and elongated

face parallel to the direction of blood flow

rest on the basement membrane by hemidesmosomes

circulatory system- endothelium

knows when there are changes in blood pressure, oxygen tension, and blood flow (responds by secreting substances that effect the tone of vascular smooth muscle)

controls blood coagulation by producing ron Willebrand factor (controls platelet adhesion to collagen in connective tissue at injury site and prevents bleeding)

produces anticoagulant substances that stop blood clotting and allows blood to freely flow in normal conditions

tunica intima

1st layer- endothelial cells

2nd layer- basement membrane

3rd layer-subendothelial connective tissue

4th layer- internal elastic lamina (wavy)

artherosclerosis

formation of deposits of yellowish plaques that contain cholesterol, lipoid material, and lipophages (macrophages)

forms the innermost layers of large and medium sized arteries

common causes: endothelial dysfunction, dyslipidemia, inflammatory and immunological factors, hypertension

cholesterol, fatty, walls, clots, stroke

deposits of _________ and __________ material accumulate in the inner layers of a blood vessel resulting in damage to the vessel ____ (disruption of the endothelium)

when cholesterol hardens, it may occlude blood flow to distant tissues and blood _____ may form

clot formation/dislodged pieces of plaque may result in vascular occlusion and __________

follicular cells

simple cuboidal cells that line the thyroid follicles of the thyroid gland

-adjacent follicles are separated by a thin layer of connective tissue

-colloids

colloid

fluid that contains hormones

hyperthyroidism

excessively high levels of thyroid hormone secretion

-lifelong

-goiter may appear (large bump on throat)

-the follicular cuboidal cells may become columnar cells when stimulated or in a state of hyperfunction

hypothyroidism

excessively low levels of thyroid hormone secretion

-the follicular squamous cells may become flattened and cells when stimulated or in a state of hyperfunction

kidneys

bowman’s capsule

glomerulus

distal convoluted tubule

prox

simple cuboidal epithelium

the appearance of this epithelium varies in different segment of the unniferous tubules

proximal tubules

the cuboidal cells have pink-stained cytoplasm and display numerous long microvilli on the apical surface

-microvilli generally fill the lumen

-pink stain due to acidophillia from numerous mitochondira that provide ATP—> necessary to power the ion pumps in the basolateral membranes of the cells

distal tubules

the cuboidal cells have short and scanty microvilli

-display less acidophillia than the proximal tubules

absorption, secretion

microvilli indicate _______ and _________ functions

substances reabsorbed in the proximal tubules

-water

-sodium

-chloride

-proteins

-glucose in the glomer

renal faconi syndrome

an impariment of proximal tubular function in the kidney resulting from an abnormality in the epithelial lining

causes: genetic defects (mostly in children) and by certain environmental factors

-rickets in children or osteromalacia in adults

some substances that should be reabsorbed into the bloodstream are instead excreted into the urine (may lead to failure to thrive in children and decreased bone mineralization)

histological features of renal faconi syndrome

-epithelial cells become squamous rather than cuboidal

-nuclei are distorted

-the basement membrane becomes wrinkled and thickened

-microvilli are reduced in number and length

simple columnar epithelium

typical of the lining of the digestive tract

apical surface has a brush border (microvilli)

goblet cells

cells with seemingly empty cytoplasm

-mucus secreting cells interspersed among the simple columnar absorptive cells (enterocytes)

celiac disease

villi flattened, damaged, or not present

disorder of the small intestine

gluten reacts with the lining of the small intestine, leading to an attack by the immune system and damage to the microvilli and villi

-if left untreated, can lead to malabsorption, anemia, bone disease, and rarely, cancer

treatment: avoid eating food with gluten

histological features: villous atrophy, inflammatory cells