PRELIM LEC 2: EPITHELIUIM Flashcards
● An avascular (having few or no blood
vessels) tissue, which lacks a direct blood supply.
● Nutrients are delivered by diffusion from blood vessels in the neighboring connective tissue.
● From the GREEK word epi meaning
“upon” and thele meaning “nipple”.
● Epithelial cell nuclei have a distinctive
shape, varying from spherical to elongated or elliptic
● MOST EPITHELIAL TISSUES ARE
RENEWED CONTINUOUSLY
EPITHELIUM
BASIC FUNCTIONS
- Protection of the body from abrasion and injury (e.g., skin and esophagus);
- Absorption of material from lumen (e.g., tubules in kidney, small and large
intestines); - Transportation of material along surface (e.g., cilia-mediated transport in the trachea);
- Secretion of mucus, hormones, and proteins (e.g., glands)
- Gas exchange (e.g., alveoli in the Lung); and
- Lubrication between two surfaces (e.g., mesothelium of pleural cavity)
Classification of Epithelial Tissues
Based on number of layers of cells:
● SIMPLE
● STRATIFIED
Based on shapes of cells in superficial layer
● Squamous epithelium
● Cuboidal epithelium
● Columnar epithelium
● Transitional epithelium (urothelium)
Specializations of the Apical Surface
(Apical Domain)
● ELONGATED , motile structures that have a greater diameter and length than microvilli
● Arise from basal bodies
● Function: aid in the transport of material along the surface of epithelial cells
CILIA
● SMALLER THAN CILIA; composed of actin microfilaments.
● Anchored to a network structure-terminal web- which contains actin filaments to stabilize the microvillus
● Function: aid in absorption
MICROVILLI
● Long microvilli; consist of actin
microfilaments
● Function: help with absorption
STEREOCILIA
Specialization of the Lateral Surface
(Lateral Domain)
- completely surround the apical cell borders to seal the underlying intercellular cleft from the outside environments.
Zonula occludens (tight junctions)
- found just beneath the tight junction, also forming a bandlike junction surrounding the entire cell and serving to attach adjacent cells
Zonula adherens (adhering junctions)
- located beneath the adhering junctions, also assist in cell to cell attachment.
Desmosomes
- are communicating junctions, provide a low-resistance channel to permit passage of ions and small molecules between adjacent cells
Gap junctions
Specializations of the Basal Surface (Basal Domain)
- a SHEET OF EXTRACELLULAR MATERIAL on all epithelial cells in contact with subjacent connective tissue at their basal surfaces.
BASAL LAMINA
● The layer below basal lamina
● These are reticular fibers made of type III collagen in the underlying connective tissues by anchoring fibrils of type VII collagen
RETICULAR LAMINA
Macromolecular components of basal
laminae
- These are LARGE GLYCOPROTEIN MOLECULES that self-assemble to form a lace-like sheet immediately below the cells’ basal poles where they are held in place by the transmembrane integrins
LAMININ
- monomers of type IV collagen contain three polypeptide chains and self assemble further to form a felt-like sheet associated with the laminin layer.
TYPE IV COLLAGEN
these glycosylated proteins and others serve to link together the laminin and type IV collagen sheets.
ENTACTIN (nidogen - a glycoprotein) AND PERLECAN (a proteoglycan with heparan sulfate side chains)
● Composed of one layer of uniform flat cell cells, which rest on the basement
membrane. THE SIMPLEST OF THE
EPITHELIA.
● Apical surfaces are smooth, and the width of the cells is greater than height.
● Function: Allows passage of materials by diffusion and filtration in sites where
protection is not important; secretes
lubricating substances in serosae.
● Locations: lining the posterior surface of the cornea; lining blood vessels and
lymphatic vessels (endothelium); lining the surface of the body cavities (pericardial, pleural, peritoneal mesothelium); and lining the alveoli of the lungs.
SIMPLE SQUAMOUS EPITHELIAL CELLS
Flattened and elongated, oriented parallel to the direction of blood flow, and resting on a basement membrane.
ENDOTHELIAL CELLS
ENDOTHELIAL CELLS
-The cells and basement membrane are linked by junctions called
_________________.
- Beneath the basement
membrane is a subendothelial layer of connective tissue.
HEMIDESMOSOMES
ENDOTHELIAL CELLS
- The wavy structure is called the internal_____________.
The endothelium, subendothelial connective tissue, and the internal elastic lamina compromise the tunica intima
ELASTIC LAMINA
A neoplasm that arises from surfaces of the pleural and peritoneal cavities. It is only occasionally found in the pericardial mesothelium
● Commonly seen in individuals who either were exposed to asbestos or who smoke.
MESOTHELIOMA
The formation of deposits of yellowish
plaques that contain cholesterol, lipid
material, and lipophages (macrophage with engulfed lipids)
● These deposits, when hardened, may
occlude blood flow to distant tissues, and blood clots may form on exposed collagen in subendothelial connective tissue.
● Clot formation or dislodged pieces of plaque may result in vascular occlusion and stroke.
ATHEROSCLEROSIS
FACTORS OF ATHEROSCLEROSIS:
- ENDOTHELIAL DYSFUNCTION
- DYSLIPIDEMIA
- INFLAMMATORY AND IMMUNOLOGIC FACTORS
- HYPERTENSION
● Composed of one layer of uniform cuboidal cells, which rest on the basement membrane.
● The cell’s height, width, and depth are
roughly equal. Nuclei are centrally placed and spherical in shape.
● Function: SECRETION & ABSORPTION
● Location: distal and collecting tubules of the kidney; found lining most of the tubules I the kidney and in some excretory glands.
SIMPLE CUBOIDAL ENPITHELIUM
● Characterized by the overproduction of thyroid hormone.
● Symptoms: nervousness, irritability,
tachycardia, increased perspiration,
difficulty sleeping, muscle weakness, warm moist skin, trembling hands, and hair loss.
● Seen most often in women 20 to 40 years of age
HYPERTHYROIDISM
● THE MOST COMMON FORM
HYPERTHYROIDISM.
● Autoimmune disease (antibodies to the TSH receptor)
● Signs: EXOPHTHALMOS
● Diagnostic test: antibody test
GRAVE’S DISEASE
● THE MOST COMMON CAUSE OF
HYPOTHYROIDISM
● Associated with enlargement of the thyroid gland (goiter)
● Characterized by high TSH and positive TPO (thyroperoxidase) antibody
HASHIMOTO’S THYROIDITIS
● Composed of one layer of columnar cells resting on the basement membrane.
● Cell’s height is greater than the width. The elongated nucleus is most often located in the basal region of the cell.
● Function: absorption, secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action.
● Location: can be found in the digestive tract, oviducts (fallopian tubes) in the female reproductive system, and ductuli efferentes testis of the male reproductive system
SIMPLE COLUMNAR EPITHELIUM
● A DISORDER OF THE SMALL INTESTINE
● If left untreated, coeliac disease can lead to malabsorption, anemia, bone disease, and, rarely, some forms of cancer.
● Histologic features: blunting of villi,
presence of lymphocytes among epithelial cells (intraepithelial lymphocytes), and increased lymphocytes within the lamina propia (connective tissue)
CELIAC (COELIAC DISEASE)
Function: secretion, particularly on mucus; population of mucus by ciliary action.
Location: Nonciliated type in male’s
sperm-carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory tract.
PSEUDOSTRATIFIED CILIATED COLUMNAR EPITHELIUM
Composed of one layer of nonuniform cells that vary in shape and height.
● Often referred to as RESPIRATORY
EPITHELIUM
● Cells appear similar to stratified cells, but all cells are in contact with the basement membrane.
● Most cells are tall columnar cells, but there are also some short basal cells, some which are stem cells.
● The most widespread type of
pseudostratified columnar epithelium is
found in the respiratory tract and has long fingerlike, motile structures called cilia on the apical surface of the cells.
PSEUDOSTRATIFIED COLUMNAR EPITHELIUM
A disease marked by ACUTE or CHRONIC INFLAMMATION of the BRONCHIAL TUBES (bronchi). The inflammation may be caused by infection (virus,bacteria) or by exposure to irritants
BRONCHITIS
● Contains several layers of cells in the
superficial layer being flattened.
● Protects the body against injury, abrasion, dehydration, and infection.
● Maybe keratinized (found in the skin -
flattened, nonnucleated dead cells - filled with tonofilaments) or nonkeratinized (same as keratinized but nucleated - found in the linings of the oral cavity, esophagus, vagina, and true vocal cords).
● Thick membrane composed of several
layer; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers.
STRATIFIED SQUAMOUS EPITHELIUM
● A COMMON CHRONIC INFLAMMATORY SKIN disease typically characterized by PINK - TO- SALMON- colored plaques with silver scales and sharp margins.
● T-lymphocyte-mediated immunologic
reactions are believed to cause the clinical feature.
● Symptoms include itching, joint pain, nail pitting, and nail discoloration.
PSORIASIS
● A complication of GASTROESOPHAGEAL REFLUX disease marked by metaplasia of the SSE of the distal esophagus into a simple columnar epithelium as a response to prolonged reflux-induced injury.
● Patients have a high risk in developing
ADENOCARCINOMA.
BARRETT SYNDROME
● Composed of two or three layers of cells.
● The top layer is columnar in shape and the basal layer is usually cuboidal in shape.
● NOT A COMMON TYPE of epithelium.
● Location: conjunctiva, some large ducts in the exocrine glands
STRATIFIED CUBOIDAL EPITHELIUM
● A clinical condition that can result from blockage of a duct or ducts, so that saliva is not able to exit into the mouth. This causes the saliva to back up inside the duct, resulting in gland swelling.
● Most common blockage is a salivary stone (calculus/calculi), which forms from salts contained in the saliva. A blocked duct and gland filled with stagnant saliva may become infected with bacteria.
● Removal of a stone may require surgery or lithotripsy (treatment by focused, high-intensity acoustic pulses).
SALIVARY GLAND SWELLING
● A stratified epithelium is often referred to as a UROTHELIUM. Lines the excretory channels leading from the kidney (renal calyces, ureters, bladder, and proximal segment or the urethra).
● May contain four to six layers in the relaxed state.
● Histological appearances can change when stretched.
● Surface cells are often described as “dome shaped” and are called dome cells (which may contain two nucleoli) or umbrella cells (they contain extra cell membrane).
TRANSITIONAL EPITHELIUM
the SPREAD OF MALIGNANT NEOPLASM from its site of origin to a remote site, usually through blood and lymphatic vessels.
METASTASIS
- a general term describing a DISORDER OF LIPOPROTEIN METABOLISM causing amounts of lipids and lipoproteins in the blood; certain dyslipidemias constitute a major risk factor in developing atherosclerosis such as hypercholesterolemia.
DYSLIPIDEMIA
- abnormal bone mineralization producing weak, soft bones; may be caused by vitamin D deficiency or kidney disorders, including renal fanconi syndrome.
OSTEOMALACIA
the reversible process by which ONE MATURE CELL TYPE CHANGES INTO ANOTHER MATURE CELL TYPE, as in squamous or metaplasia of respiratory or glandular
METAPLASIA
● Composed of epithelial tissue and can be classified as endocrine and exocrine
according to how the secretory product
leaves the gland
GLANDS
● Release their products into interstitial fluid or directly into the bloodstream
ENDOCRINE GLANDS
● Secrete their products either through DUCTS into the lumen of an organ or directly onto the body surfaces
EXOCRINE GLANDS
collection of neutrophils and neutrophil debris WITHIN THE PARAKERATOTIC SCALE in the skin disease psoriasis.
MICROABSCESS
- collection of neutrophils WITHIN THE EPIDERMIS, abutting the parakeratotic scale in the skin disease psoriasis.
MICROPOSTULE
PERSISTENCE OF THE NUCLEI OF KERATINOCYTES into the stratum corneum of the skin or mucous membranes; parakeratotic scales containing neutrophils are seen in the skin.
PARAKERATOSIS
Glands
Can be classified by product:
a WATERY proteinaceous fluid (e.g. parotid, gland of von Ebner of the tongue, pancreas, and sweat gland)
SEROUS GLANDS
secrete mucus, a viscous
mixture of glycoprotein and water (e.g.
goblet cells in the small and large
intestine, respiratory epithelium, some
glands in hard and soft palates, and
stomach epithelium)
MUCOUS GLANDS
have both serous and mucous secretions (e.g.submandibular, sublingual, tracheal glands
MIXED GLANDS (SEROMUCOUS)
produce lipids (e.g. skin
SEBACEOUS GLANDS
Classified by mechanisms or secretion
● MOST COMMON MODE
● The secretory products are released from the cell by EXOCYTOSIS WITHOUT THE LOSS OF CELL MATERIAL (e.g. release of zymogen granules by pancreatic acinar cells)
MEROCRINE
● The secretory product is released together WITH PART OF THE APICAL CYTOPLASM of the secretory cell (lipid secretion of the mammary gland)
APOCRINE
● The secretory product is released by
DISINTEGRATION OF THE ENTIRE CELL The secretory cell dies and a new secretory cell is formed from a nearby basal cell (e.g. sebum released by the cells of sebaceous glands)
HOLOCRINE
Classified by morphology
● The secretory products are released directly ONTO THE SURFACE of an epithelium (e.g. goblet cell)
UNICELLULAR
Consist of numbers of secretory cells
arranged in a different organizations that can be classified generally, simple glands and compound glands, which can also be subclassified according to their morphology:
MULTICELLULAR
have no ducts, straight tubules and can be found in small and large intestines.
SIMPLE TUBULAR GLANDS
- DON’T have ducts, secretory cells are split into two or more tubules and can be found in the stomach.
SIMPLE BRANCHED TUBULAR GLANDS
have a LONG DUCT, secretory cells are formed by coiled tubules.
Simple coiled tubular glands
have SHORT, unbranched ducts; secretory cells are arranged in acini form.
Simple acinar glands
have a short, unbranched duct, secretory cells are formed into branched acini.
Simple branched acinar glands
have branched ducts, secretory cells are formed into branched tubules (e.g. brunner glands)
Compound tubular glands
branched ducts, secretory units are branched acini.
Compound acinar glands
branched ducts, secretory units are formed by both an acinar component and a tubular component (e.g. submandibular and sublingual glands).
Compound tubuloacinar glands
FUNCTIONAL EPITHELIUM
- SEROUS LINING of cavities such as pericardium, pleura, peritoneum for lubrication
Mesothelium
made up of FLAT CELLS that lines the
blood vessels
Endothelium
BASKET CELLS to remodel the scars in the skin
Myoepithelium
lining of the uterus
Endometrium
layer of the ovaries and seminiferous tubules
Germinal epithelium
for secretions
Glandular epithelium
