Histology Lecture

Question 1

Specializations of Epithelial Cells

Answer 1

Epithelial cells have several structural specializations. For the epithelium as a whole to perform its functions, individual epithelial cells may be specialized for,
1. Move fluids over the epithelium (protection)
2. Move fluids through the epithelium (permeability)
3. Produce secretions (protection and messengers)

Question 2

Polarity (characteristic of epithelia)

Answer 2

The specialized epithelial cell is often divided into two functional regions, which means the cell has strong polarity.
1. Apical surfaces - Microvilli increase absorption or secretion; Cilia (ciliated epithelium) move fluid
2. Basolateral surfaces - include both the base (basal surface), where the cell attached to underlying epithelial cells or deeper tissues, and the sides (lateral surfaces), where the cell contacts its neighbors

Question 3

Glandular Epithelia

Answer 3

gland cells that are specialized for secretions

Question 4

Clear Layer (lamina lucida)

Answer 4

-Thin layer
-Secreted by epithelia
-Barrier to proteins

Question 5

Dense layer (lamina densa)

Answer 5

-Thick fibers
-Produced by connective tissue
-Strength and filtration

Question 6

Epithelial Maintenance and Repair

Answer 6

-Epithelia are replaced by division of germinative cells (stem cells)
-Near basement membrane

Question 7

Simple Squamous Epithelium

Answer 7

This type of epithelium is located in protected regions where absorption and diffusion takes place. Examples are the respiratory exchange surfaces of the lungs, the lining of the thoracic and the lining of the heart and blood vessels

Question 8

Mesothelium

Answer 8

Lines body cavities

Question 9

Endothelium

Answer 9

Lines heart and blood vessels

Question 10

Stratified Squamous Epithlium

Answer 10

generally located where mechanical stresses are severe. The surface of the skin and the lining of the mouth. esophagus, and anus are areas where this type of epithelium protects against physical and chemical attacks

Question 11

Simple Cuboidal Epithelium

Answer 11

provides limited protection and occurs where secretion or absorption takes place.

Question 12

Stratified Cuboidal Epithelia

Answer 12

Sweat ducts and mammary glands

Question 13

Simple Columnar Epithelium

Answer 13

Absorption or secretion takes place, such as in the small intestine. In the stomach and large intestine, the secretions of simple columnar epithelia protect against chemical stresses.

Question 14

Pseudostratified Columnar Epithelium

Answer 14

Cilia movement. Epithelia of this type line most of the nasal cavity, the trachea (windpipe), the bronchi (branches of the trachea leading to the lungs), and portions of the male reproductive tract.

Question 15

Transitional Epithelium

Answer 15

permits repeated cycles of stretching without damage. A transitional epithelium is found in regions of the urinary system, such as the urinary bladder

Question 16

Stratified Columnar Epithelium

Answer 16

Protection along portions of the pharynx, epiglottis, anus, and urethra, as well as along a few large excretory ducts.

Question 17

Endocrine Glands

Answer 17

Produce endocrine secretions called hormones. These hormones enter the bloodstream for distribution throughout the body. Hormones regulate or coordinate the activities of various tissues, organs, and organ systems. Because their secretions are not released into ducts, endocrine glands are often called ductless glands..

Question 18

Exocrine Glands

Answer 18

Produce exocrine secretions onto the epithelial surface through ducts

Question 19

Merocrine Secretion (Exocrine method of secretion)

Answer 19

-Produce in Golgi apparatus
-Release by vesicles (exocytosis)
-For example, sweat glands

Question 20

Apocrine Secretion (Exocrine method of secretion)

Answer 20

-Produced in Golgi apparatus
-Released by shedding cytoplasm
-For example, mammary glands

Question 21

Holocrine Secretion (Exocrine method of secretion)

Answer 21

-Released by cells bursting, killing gland cells
-Gland cells replaced by stem cells
-For example, sebaceous glands

Question 22

Serous Glands ( Exocrine type of secretion)

Answer 22

Watery secretions

Question 23

Mucous Glands (Exocrine type of secretion)

Answer 23

Secrete mucins

Question 24

Mixed Exocrine Glands (Exocrine type of secretion)

Answer 24

Both serous and mucous

Question 25

Unicellular Glands (Gland Structure)

Answer 25

-Mucous (goblet) cells are the only unicellular exocrine glands
->Scattered among epithelia
->For example, in intestinal lining

Question 26

Epithelial Tissue

Answer 26

covers exposed surfaces, lines internal passageways and chambers, and forms glands

Question 27

Connective tissue

Answer 27

fills internal spaces, provides structural support for other tissues, transports materials within the body, and stores energy

Question 28

Muscle Tissue

Answer 28

specialized for contraction and includes the skeletal muscles of the body, the muscle of the heart, and the muscular walls of hollow organs

Question 29

Nervous Tissue

Answer 29

carries information from one part of the body to another in the form of electrical impulses

Question 30

Cellularity (characteristic of epithelia)

Answer 30

epithelia are made almost entirely of cells bound closely together by interconnections known as cell junction

Question 31

Attachment (characteristic of epithelia)

Answer 31

Epithelia cells display attachment which means that the basal surfaces of the cells are attached to a special layer called the basal lamina or basement membrane. The basal lamina or membrane supports the epithelium and anchors it firmly to the underlying connective tissue.

Question 32

Avascularity (characteristic of epithelia)

Answer 32

Epithelia are avascular which means that they lack blood vessels. Epithelia cells get nutrients by diffusion or absorption across either the exposed or the attached epithelial surface

Question 33

Regeneration (characteristic of epithelia)

Answer 33

Epithelial cells that are damaged or lost at the exposed surface are continuously replaced through stem cell division in the epithelium. The rate of cell division in epithelia is much higher than in other tissues.

Question 34

Intracellular Connections

Answer 34

Large areas of opposing plasma membranes are interconnected by transmembrane proteins called cell adhesion molecules (CAMs), which bind to each other and to extracellular materials. The membranes of adjacent cells may also be bonded by a thin later of proteoglycans that contain polysaccharide derivatives known as glycosaminoglycans (GAGs), most notably, hyaluronan (hyaluronic acid)

Question 35

Cell Junctions

Answer 35

specialized areas of the plasma membrane that attach a cell to another cell or to extracellular materials.

Question 36

Tight Junctions

Answer 36

formed by the fusion of the outer layers of two plasma membranes. Tight junctions prevent the diffusion of fluids and solutes between the cells. A continuous adhesion belt lies deep to the tight junction. This belt is tied to the microfilaments of the terminal web.

Question 37

Gap Junction

Answer 37

two cells are held together by channel proteins called connexons. Two aligned connexons form a narrow passageway that lets small molecules and ions pass from cell to cell. Gap junctions in cardiac muscle tissue and smooth muscle tissue are essential in coordinating muscle cell contractions.

Question 38

Spot Demosomes

Answer 38

-Ties adjacent cells together
-Allow bending and twisting

Question 39

Hemidesmosomes

Answer 39

Attach a cell to extracellular structures, such as the protein fibers in the basement membrane

Question 40

Functions of Epithelial Tissue

Answer 40

-Provide Physical Protection
-Control Permeability
-Provide Sensation
-Produce Specialized Secretions (glandular epithelium)