Lecture 4

Question 1

what are keratins?

Answer 1

translucid scleroproteins formed by 6-8 polypeptides

Question 2

how do melanocytes make melanin?

Answer 2

via melanosomes:
- tyrosine turns into 3,4 dihydroxy phenylalanine by tyrosinase
- then it is turned into dopaquinone by tyrosinase
- then it turns into melanin

Question 3

what are the different types of melanin?

Answer 3

eumelanin (brown) and pheomelanin (red)

Question 4

what are melanocytes and where are they found?

Answer 4

ovoid-shaped cells (found in the stratum germinativum) with projections intertwined in the stratum spinosum

Question 5

how does melanin go to epithelial cells?

Answer 5

melanosomes are phagocytosed (part of the projections) into the cells of the spinosum and it sits on the edge of the nucleus, which protects it (the DNA) from UV rays

Question 6

describe the cells of the sebaceous gland?

Answer 6

non-squamous stratified epithelium

Question 7

what is contained in sebacous cells?

Answer 7

lipid droplets with cholesterol, phospholipids, triglycerides, and glycogen

Question 8

what stimulates and inhibits sebum release from sebaceous glands?

Answer 8

stimulated by androgens and inhibited by estrogens

Question 9

what is contained in sweat?

Answer 9

water, urea, ammonia, NaCl

Question 10

role of sweat glands

Answer 10

thermoregulation by evaporation cooling

Question 11

type of secretion of sebaceous glands

Answer 11

holocrine secretion

Question 12

type of secretion of sweat glands

Answer 12

merocrine secretion

Question 13

types of secretion

Answer 13

merocrine, apocrine, and holocrine

Question 14

merocrine secretion

Answer 14

secretory vesicles released only

Question 15

apocrine secretion

Answer 15

part of the cell pinched off

Question 16

holocrine secretion

Answer 16

mature cell dies and becomes secretory product

Question 17

shape of the sweat gland

Answer 17

simple coiled tubular

Question 18

what type of fluid is released from sweat glands?

Answer 18

serous (watery, protein-rich fluid)

Question 19

what are the different parts of the sweat gland and where is each found?

Answer 19

secretory portion: hypodermis
duct (excretory portion): dermis and hypodermis

Question 20

Difference Between Secretory Portion and Ductal Portion of Sweat Gland

Answer 20

ductal:
- cell size is small
- 2 cell layers ( stratified cuboidal epithelium)
- darkly stained (basophilic)
- small in diameter
- not surrounded by myoepithelial cells

secretory portion:
- cell size is larger
- one cell layer (simple columnar)
- lightly stained
- large in diameter
- surrounded by myoepithelial cells

Question 21

where are trichohyalin granules found?

Answer 21

Huxley’s layer in the internal root sheath

Question 22

cells found in the sebaceous gland?

Answer 22

basal cell layer (stem cells) that go up and turn into sebaceous cells that slowly fill with lipid (sebum)

Question 23

describe the cells of the external root sheath.

Answer 23

cuboidal keratinized cells

Question 24

describe the cells of the internal root sheath.

Answer 24

• Henle’s layer : squamous
• Huxley’s layer: cuboidal – has trichohyalin granules (acidophilic)
• Cuticle of IRS: squamous cells (partially keratinized)