Chp 4, Epithelial Tissue

Question 1

Tissues and the (4) basic types

Answer 1

• group of cells with similar in structure that perform common/related function
  1. Epithelial
  2. Connective
  3. Muscle
  4. Nervous

Question 2

Histology

Answer 2

study of tissues

Question 3

Epithelial Tissue / Epithelium

Answer 3

• sheet of cells that covers a body surface / lines a body cavity
• Two forms in the body:
  1. Covering and lining epithelia - on external/internal surfaces
  2. Glandular epithelia - secretory tissue in glands
• Main function: protection, absorption, filtration, excretion, secretion, and sensory receptors

Question 4

(5) Shared characteristics of Epithelial Tissue

Answer 4

1. Polarity
2. Specialized Contacts
3. supported by connective tissues
4. avascular, but innervated
5. regeneration

Question 5

apical surface

Answer 5

• the upper, free surface of epithelial tissue exposed to the body exterior or cavity of an internal organ
• typically smooth, but can also have microvilli / cilia

Question 6

basal surface

Answer 6

• lower, attached side of epithelial tissue, faces inward toward the body
• attaches to the basal lamina

Question 7

basal lamina

Answer 7

• adjacent to the basal surface, this is a thin support sheet that holds the basal surface to underlying cells
• acts as a selective fiber that determines which molecules diffuse from underlying connective tissue are allowed to enter the epithelium
• upper part of the basal basement

Question 8

Polarity of Epithelial Cells

Answer 8

-a top (apical) and bottom (basal) surface that different in structure and function

Question 9

Specialized Contacts

Answer 9

• epithelial cells fit closely together to form sheets (except for glandular epithelial). they are connected
• The are connected by lateral contacts tight junctions and desmosomes.
• Tight junctions prevent passant of material between the cells
• desmosomes give structural support and help prevent tearing

Question 10

Connective Tissue that supports Epithelial cells

Answer 10

• epithelial cells rest on/are supported by connective tissue called the ‘basement membrane’
• basement membrane is a layer of basal lamina and deep to that is the reticular lamina

Question 11

Avascular, but innervated

Answer 11

• epithelial tissue do not contain any blood vessels
• they are supplied by nerve fibers
• get nourished by substances diffusing from blood vessels in the underlying connective tissue

Question 12

Regeneration

Answer 12

• epithelial cells have a high regenerative capacity (cell division - mitosis)
• stimulated by loss of apical-basal polarity and broken lateral contacts

Question 13

Classification of Epithelia (two names)

Answer 13

• The first name is the number of cell layers (simple or stratified)
• Second name is shape of cells or shape of apical layer if stratified

Question 14

Shapes of Epithelial cells

Answer 14

1. squamous - flattened and scale like
2. cuboidal - box-like, cube
3. columnar - tall, column-like

Question 15

Simple epithelia

Answer 15

-single layer epithelia involved in absorption, secretion, or filtration

Question 16

endothelium

Answer 16

• simple squamous epithelia found in lining of lymphatic vessels, blood vessels, and heart
• the thinness encourages the efficient exchange of nutrients and wastes between bloodstream and surrounding cells

Question 17

Mesothelium

Answer 17

-simple squamous epithelium that are found in serous membranes, membranes lining the ventral cavity and covering the organs in the cavity

Question 18

simple squamous epithelia

Answer 18

• single layer with flat cells and sparse cytoplasm

- very thin and permeable, found where filtration/exchange by rapid diffusion is needed - kidneys/lungs

Question 19

simple cuboidal epithelium

Answer 19

• single layer of cuboidal cells
• involved in secretion and absorption
• this epithelium forms the walls of small ducts of glands and kidney tubules

Question 20

simple columnar epithelium

Answer 20

• single layer of column shaped epithelium cells - these are tall, closely packed cells.
• associated with absorption and secretion
• some have microvilli/cilia (which make it good for absorption and secretion)
• lines digestive tract, gall bladder, ducts of some glands, bronchi, and uterine tubes

Question 21

psuedostratified columnar epithelium

Answer 21

• columnar cells have varying heights (which makes it look stratified) but all of them rest on the basement membrane - so actually simple
• secretes and absorbs

Question 22

stratified epithelium tissue

Answer 22

• two or more layers of cells
• new cells regenerate from below (old cells on top)
• more durable than simple epithelium
• protection is the mane role

Question 23

stratified squamous epithelium

Answer 23

• most widespread of stratified epithelia
• many layers
• apical layer is squamous, with deeper layers cuboidal/columnar
• located in areas of wear/tear like skin
• keratinized cells - have the the tough protein keratin OR
• non-keratinized - without keratin

Question 24

Stratified cuboidal epithelia

Answer 24

• pretty rare
• found in sweat and mammary glands
• usually only 2 layers

Question 25

stratified columnar epithelium

Answer 25

- very limited - small amounts in pharynx, male urthera, and line some glandular ducts - only apical layer is columnar

Question 26

transitional epithelium

Answer 26

- forms lining of hollow urinary organs - bladder, ureters, urethra - these cells can compress/stretch, allowing more volume in the organ - basal layer are cuboidal/columnar

Question 27

Gland and gland classification

Answer 27

- one ore more cells that make and secrete a product | - classified by site of product releases (endocrine/exocrine) and number of cells (unicellular/multicellular)

Question 28

endocrine glands

Answer 28

- glands that secrete internally, like hormones - ductless - released by exocytosis into extracellular space where it can enter blood, lymphatic fluid, or to specific target organs and prompt a certain response - mostly multicellular with a few unicellular (part of diffuse endocrine system)

Question 29

exocrine glands

Answer 29

- gland that secrete externally onto body surfaces (skin) or into body cavities - more numerous than endocrine glands - these secrete into ducts - can by unicellular / multiceullar

Question 30

Unicellular exocrine glands

Answer 30

- goblet and mucous cells - found in epithelial linings of intestinal and respiratory tracts - both cells produce mucin, that dissolves in water forming mucous

Question 31

Multicellular exocrine glands

Answer 31

- have two parts - a duct and a secretory unit - usually surrounded by supportive connective tissue that supplies blood and nerve fibers to gland - the connective tissue also forms fibrous capsule around gland and extend into the gland, dividing into lobes - classified by structure (simple/compound &secretory unit) and mode of secretion

Question 32

Simple vs. Compound multicellular exocrine Glands

Answer 32

Classification of multicellular exocrineglands by structure: simple glands - unbranched duct compound glands - branched duct

Question 33

secretory units of multicellular exocrine glands - 3 types

Answer 33

1. tubular 2. aveolar / acinar - sacs 3. tubuloalveolar

Question 34

modes of secretion of multicellular exocrine glands (3)

Answer 34

1. merocrine 2. holocrine 3. apocrine

Question 35

merocrine

Answer 35

multicellular exocrine gland form of secretion by exocytosis | ex - sweat, pancreas

Question 36

holocrine

Answer 36

- mode of secretion of multicellular exocrine glands where the product accumulates in duct until it ruptures releasing product and dead cell fragments ex. sebaceous oil glands

Question 37

apocrine

Answer 37

mode of secretion of multicellular exocrine glands -product accumulates within duct, but only apex ruptures not actually sure if this exists in humans, maybe mammary cells