New Deck

Question 1

epidermis: what kind of cells? what important molecule is produced?

Answer 1

stratified squamous that produces keratin.

Question 2

desrcibe the dermis

Answer 2

fibrous connective tissue containing blood vessels, nerves and sensory receptors

Question 3

hypodermis or subcutis: what kind of tissue is found here?

Answer 3

mainly adipose tissue, blood vessels and nerves.

often referred as the superficial fascia

Question 4

what is desquamation?

Answer 4

friction and exposure to the environment that results in the sloughing off of the cells

Question 5

what is keratinization?

Answer 5

keratinocytes in the basal layer are pushed up, and they mature as they go upwards.

keratinocyte die as they reach the surface; all that remains in the skin surface keratin

Question 6

what is a keratinocyte?

Answer 6

keratinocyte is a generic name for the epithelial cells of the epidermis- but they look different depending on the layer that they are in.

Question 7

stem cells in the basal layer undergo what kind of division?

Answer 7

asymmetric division- one a stem cell and other a keratinocyte that will begin maturation.

Question 8

squamous or spinous layer- what kind of cells are in this layer? what are the characteristics of the cells in this layer?

Answer 8

formed by polyhedral keratinocytes.

they have pale nucleus, and very visible nucleolus- an indication that it is actively producing cytokeratin.

cytokeratin goes on to form bundles of tonofibrils in the cytoplasm, which are important for desmosome integrity

Question 9

cytokeratin forms what?

Answer 9

tonofibrils in the cytoplasm, which are important for desmosome integrity

Question 10

granular layer- what do keratinocytes in this layer produce? how ar ethe keratinocytes in this layer characterized?

Answer 10

keratinocytes in this layer produce keratohyaline granules, which attach to tonofibrils.

**keratin = ** tonofibrils + keratohyaline granules

keratinocytes in this layer are characterized by the presence of lamellar granules in their cytoplasm. these granules contain lipids that are exocytosed from cells to form a barrier to protect against water loss through skin.

at this layer, keratinocytes lose their nucleus and cytoplasm is packed with keratin.

Question 11

psoriasis

Answer 11

increased number of proliferating stem cells in the basal and spinous layers of the epidermis. as a result, cells in the epidermis are replaced more quickly

leads to improper formation of tonofibrils and keratohyaline granules => defective keratinization

Question 12

stratum corneum: what kind of cells are here?

Answer 12

non-nucleated keratinocytes called squames

Question 13

melanocytes: where are they?

are they attached to other cells via desmosomes?

what are their specialized lysosomes called?

Answer 13

melanocytes have cell processes that extend into the squamous layer.

they are not attached to other cells

melanosomes : tyrosine is converted to DOPA then melanin

Question 14

how does skin get its color?

Answer 14

when keratinocytes in the basal layer and lower squamous layer phagocytize the tips of the melanocyte processes which contain melanosomes (which contain melanin)

Question 15

how do differences in skin pigmentation arise in different races?

Answer 15

number and size of melanosomes within each melanocyte.

melanocytes have pale staining cytoplasm

Question 16

what are Langherhan’s cells (or dendritic cells)?

where are they generated?

where are they found?

are they anchored to adjacent cells by desmosomes?

what are their functions?

Answer 16

intra-edpidermal antigen recognition cells

generated in the bone marrow then they travel through the blood to reach the skin. they are part of the immune system

they are found in the squamous layer

they are not bound to adjacent cells.

they phagocytose foreign antigens, and travels through the lymphatic system to a lymph node to intiate a response there.

important in the rejection of skin allografts

protect the skin from tumor formation

Question 17

what kind of cells are these:

Answer 17

Langerhan’s cells

Question 18

what are Merkel cells?

what layer are they found in?

Answer 18

they are mechanoreceptors that are sensitive to light touch

they are found in the basal layer

Question 19

Answer 19

Question 20

what is the papillary layer?

Answer 20

thin, loose connective tissue layer

fibroblasts, mast cells, macrophages and extravasated leukocytes

Question 21

what is the reticular layer?

Answer 21

thick dense connective tissue rich in collagen
(mainly type I), elastic fibers

less cells than papillary layer.

Question 22

Paccinian corpuscles

Answer 22

sense deep pressure and vibration in the palms of the hand and soles of the feet.

Question 23

cutaneous plexus

Answer 23

blood vessels, junction of hypodermis and dermis

Question 24

papillary plexus

Answer 24

located at junction of papillary layer of the dermis and the epidermis.

Question 25

hypodermis: what kind of cells are found here?

Answer 25

layer formed by collagenous fibrous septa filled with adipose tissue

Paccinian corpuscles

Question 26

blood circulation to the skin orginates from which layer of the skin?

Answer 26

hypodermis

Question 27

collagen type VII

Answer 27

found anchoring the **dermoepidermal basement membrane ** to the underlying dermis (which contains collagen type III and type I).

Question 28

basal cells are connected to the dermoepidermal basement membrane by

Answer 28

hemidesmosomes

Question 29

eccrine sweat glands

Answer 29

secrete sweat

Question 30

apocrine glands

Answer 30

axilla and groin areas and secrete sweat

Question 31

which muscle pulls the hair erect

Answer 31

arrector pilli muscle

Question 32

what are the three layers of the hair follicle

Answer 32

medulla (innermost)

cortex

cuticle (outermost)

Question 33

what is an acinus?

Answer 33

group of cells arranged in a cluster that produce sebum

has its own duct or conducting portion

Question 34

histologically, a sweat gland contains

Answer 34

1) a secretory unit in the upper hypodermis or lower dermis
2) a duct that projects vertically towards the surface of the skin

Question 35

Answer 35

B- sagittal section of eccrine sweat gland

S- secretory acini

D duct sectins

My myoepithelial cells