Histology of Skin

Question 1

Be able to describe the location, structure, and distinguishing features of the following epidermal layers:

stratum germinativum (stratum basal):

Answer 1

Deepest layer, Basal layer
Mitotically active
Hemidesmosomes & desmosomes
Polyribosomes in cytoplasm
Intermediate filaments (keratin type) in cytoplasm

Question 2

Be able to describe the location, structure, and distinguishing features of the following epidermal layers:

stratum spinosum

Answer 2

cells look like they have spines on them. has LAMELLAR bodies made of LIPIDS

‘Prickle’ cell layer (SPINEY cells)
Mitotically active
Desmosomes hold cells together
Polyribosomes
Intermediate filaments (keratin type) & tonofibrils
Membrane coating granules (keratinosomes) (golgi)

Question 3

Be able to describe the location, structure, and distinguishing features of the following epidermal layers:

stratum granulosum

Answer 3

No mitotic activity
Keratohyalin GRANULES
Nuclei become pyknotic

Question 4

Be able to describe the location, structure, and distinguishing features of the following epidermal layers:

stratum corneum

Answer 4

Outermost layer
Cells are dead and flat
Cells are completely ‘keratinized’
PILES OF CELLS

Question 5

Be able to describe the process of keratinization.

Answer 5

Synthetic phase:
Intermediate filaments
Membrane coating granules
Keratohyalin granules
Filaggrin and trichohyalin

Degradative phase:
Membrane coating granule discharge
Lysosomal degradation of organelles
Consolidation of filaments and keratohyalin into a fibrous amorphous mass

Question 6

What are the hard Keratins

Answer 6

No granular cell layer phase

Hair & nails

Question 7

What are soft Keratins

Answer 7

Granular cell layer phase

Epidermis and internal root sheath of hair

Question 8

Be able to describe what the hypodermis is and where it is found?

Answer 8

Loose connective tissue
Frequently contains lots of fat cells
E.g., panniculus adiposus

Question 9

Be able to describe the location, structure, and distinguishing features of the following dermal layers:

papillary layer of the dermis

Answer 9

1. Superficial layer of dermis
   a. immediately beneath basement membrane
2. Composition
   a. Loose connective tissue
   (1) Thin bundles of collagen fibers
   (2) Some reticular and elastic fibers
   (3) More cellular than reticular layer
3. Vascular papillae
   a. Papillae contain capillary loop projections
   (1) Only source of nourishment for epithelial cells
   (2) Thermoregulatory devices
4. Nervous papillae
   a. Contain special nerve terminations
   (1) Meissner’s corpuscles (mechanoreceptors)
   (2) Krause end bulbs (mechanoreceptors)

Question 10

Be able to describe the location, structure, and distinguishing features of the following dermal layers:

reticular layer of the dermis

Answer 10

1. Deep layer of dermis
   a. Between papillary layer of dermis and hypodermis
2. Composition
   a. Dense irregular connective tissue
   (1) Coarse, dense, interfacing bundles of collagen fibers (type I collagen)
   (2) Some reticular fibers, many elastic fibers
   (3) Less cellular than papillary layer
   b. Predominant direction of all fibers is parallel to surface
   (1) Direction of fibers creates lines of skin tension – Langer lines (specific for surgeons)
   (a) These differ in different regions of body
   (b) Surgical incisions parallel to these lines gape less and heal with less
   scarring

Question 11

Be able to describe the formation of melanin, the cells involved in melanin formation, and skin pigmentation

Answer 11

Produced by cells called melanocytes, Melanosome formation

Question 12

Be able to describe the functions of the following cells: Merkel cells

Answer 12

associated with unmyelinated sensory nerves

(1) probably involved in sensory reception

Question 13

Be able to describe the functions of the following cells: Langerhans cells, (APC)

Answer 13

a. Derived from bone marrow precursors
b. Immunological function
(1) Cell surface Fc (antibody) and C3 (complement) receptors
(2) Phagocytose and process foreign antigens
(3) Migrate to local lymph nodes; present epitopes of processed foreign antigens to T-lymphocytes

Question 14

Be able to describe the functions of the following cells: melanocytes

Answer 14

a. Produce melanin granules (melanosomes); melanin production dependent upon
the enzyme tyrosinase
b. Donate melanin granules to cells in stratum germinativum and stratum spinosum: cytocrine secretion

Question 15

Be able to describe the generalized pattern of skin vascularization

Answer 15

Largest arteries reside in subcutaneous tissue
Rete cutaneum
Rete subpapillare

Question 16

Be able to define and describe the function of what an arteriovenous anastomosis is.

Answer 16

AVA shunts, important in regulation. reduces heat loss. shuts down when in a hot environment. Thermoregulation.

Question 17

Be able to describe the structure and function of the following associated integumentary structures:

hair

Answer 17

hair shaft, hair follicle and external root sheath

Question 18

Be able to describe the structure and function of the following associated integumentary structures:

nails

Answer 18

1. Nail plate: closely compacted horny scales
   a. Hard keratin
2. Nail bed
   a. Stratum malpighian (stratum basale & stratum spinosum) cells only
   b. No stratum granulosum
   c. Nail plate slowly slides over nail bed
3. Nail matrix (MITOTIC ACTIVITY)
   a. Most proximal portion of nail bed
   b. Cells proliferate here – push nail distally
4. Other terms associated with the nail
   a. Nail fold
   b. Nail groove
   c. Nail wall
   d. Eponychium
   e. Hyponychium
   f. Lunula

Question 19

Be able to describe the structure and function of the following associated integumentary structures:

eccrine or merocrine sweat glands

Answer 19

Secretory portion
Simple cuboidal epithelium; small lumen
Deep dermis or hypodermis
Clear cells (watery secretion) & dark cells (mucous secretion)
Myoepithelial cells (contractile properties)
Secretions contain: KCl; NaCl; ammonia; urea
Duct portion
Resorbs much of NaCl and KCl
Stratified cuboidal epithelium
Sympathetic innervation
almost no lumen***

Question 20

Be able to describe the structure and function of the following associated integumentary structures:

arrector pili muscle

Answer 20

Bundles of smooth muscle
Sympathetic innervation
Anchored in:
Hair follicle sheath
Papillary layer of dermis
Help to:
Produce ‘goose bumps’
Move sebaceous gland products

Question 21

describe sebaceous glands

Answer 21

Usually associated with hair follicles
Exceptions: eyelids; areolae of mammary glands; labia minora; glans of penis; corners of lips
Holocrine secretion (oil rick substance)
Acne: male hormone (androgen) related
Males: testes & adrenal cortex
Females: ovaries & adrenal cortex
Blackheads (blocked up sebaceous glands still open to the surface) white heads, not open to the surface

Question 22

Be able to describe the structure and function of the following associated integumentary structures:

Apocrine Sweat Glands

Answer 22

Secretory portion
Simple cubodial/columnar epithelium
Restricted locations: axilla; areolae; anogenital
Myoepithelial cells
Odorless viscous secretion which becomes odored when acted on by bacteria
Duct portion
Empty into hair follicles*
stratified cuboidal epitheliun
Sympathetic innervation
visual lumen***

Question 23

Encapsulated Nerve Endings

Answer 23

Meissner’s corpuscles: touch (penis)

Pacinian corpuscles: pressure (looks like onion), senory nerve fiber in the middle

Question 24

Be able to describe the process of skin wound healing.

Answer 24

cells increase mitotic rate, fibroblasts migrate to produce collagen.

Question 25

the different kinds of skin grafts

Answer 25

**Split skin grafts (prefered) leave hair follicle and sweat gland
Full-thickness grafts

Question 26

Be able to describe the differences in skin damage due to sunburn, first, second, and third degree burns.

Answer 26

first, red and goes away
second degree-blistering, epidermis and dermis
third, destruction of epiidermis and dermis