2.2 skin histology

Question 1

Skin functions

Answer 1

barrier, immunity. sensory functions, exocrine functions, homeostasis, excretion

Question 2

Skin layers

Answer 2

Epidermis, dermis, hypodermis

Question 3

Epidermis: characteristics

Answer 3

superficial layer
resist abrasion 
ectoderm 
avascular 
nourishment from diffusion of capillaries in papillary layer of dermis

Question 4

Dermis: characteristics

Answer 4

contains hair, glands, ducts and bvs

mesoderm

Question 5

Hypodermis: characteristics

Answer 5

subcutaneous tissue
loose CT
adipose tissue

Question 6

Epidermis layers `

Answer 6

Stratum corneum
stratum lucidium
stratum granulosum
stratum spinosum
stratum basale

Question 7

Stratum corneum

Answer 7

superficial layer

keratinised cells - flat + non-nucleated

Question 8

stratum lucidium

Answer 8

thick skin, flat cells

Question 9

stratum granulosum

Answer 9

keratohyalin granules
terminal differentiation - nucleus + other organelles degenerate -> cell death
flat + polygonal cells

Question 10

stratum spinosum

Answer 10

thickest layer
keratin fibre synthesis
cuboidal cells

Question 11

stratum basale

Answer 11

high mitotic activity
on basement membrane
cuboidal/low columnar

Question 12

Epidermal cells

Answer 12

keratinocytes
melanocytes
merkel cells
langerhan cells

Question 13

Desquamation

Answer 13

cells in deeper layer undergo mitosis
cells move up toward the surface
older cells slough off
epidermis renewed ~15 days

Question 14

keratinisation

Answer 14

cells move upward through layer fill with keratin and die

layer resists abrasion + forms waterproof layer

Question 15

thick vs thin skin

Answer 15

thick - hairless, thick stratum corneum, stratum lucidium present, 5 layers
thin - hair, thin stratum corneum, no stratum lucidium , 4 layers

Question 16

dermis: characteristics

Answer 16

structural strength
connective tissue with: fibres, fibroblasts, macrophages, adipocytes
contains: BVs, nerves, hair follicles, smooth muscles, glands

Question 17

dermis: function

Answer 17

support endothelial cells of epidermis
connect epidermis to hypodermis
changes in thickness

Question 18

dermis: layers

Answer 18

papillary

reticular

Question 19

dermis: papillary layer

Answer 19

superficial
loose ct with elastic fibres, collagen fibres
dermal papillae

Question 20

dermis: reticular layer

Answer 20

dense irregular ct
thick collagen bundles
coarse elastic fibres
hair follicles, nerves, adipose, oil glands

Question 21

thick vs thin skin: dermal papillae

Answer 21

thick skin - well formed rete ridge system

thin skin - poorly formed rete ridge system

Question 22

rete ridge system

Answer 22

interface between epidermis + dermis held together by interlocking epidermal ridges
prevents epidermal separation

Question 23

free nerve endings

Answer 23

fine touch

heat and cold

Question 24

pancinian corpuscle

Answer 24

crude touch
high freq vibrations
reticular dermis

Question 25

meissner's corpuscle

Answer 25

discriminative touch low freq vibrations in papillary dermis

Question 26

hypodernis: consists of

Answer 26

``` loose CT adipose cells fibroblasts macrophages contains 50% of body's adipose tissue ```

Question 27

hypodermis: function

Answer 27

energy source insulation padding supplies the dermis

Question 28

determination of skin colour

Answer 28

pigment blood circulation through skin thickness of stratum corneum

Question 29

melanin

Answer 29

protect against UV eumelanin: brown -> black pigments pheuomelanin: yellow -> red pigments

Question 30

melanocytes

Answer 30

produce melanin then passed into keratinocytes via dendritic processes that extend between keratinocyte

Question 31

melanocytes in light vs dark skin

Answer 31

light skin: stratum basale | dark skin: stratum granulosum

Question 32

accessory skin structures

Answer 32

hair sebaceous glands sweat glands

Question 33

type of sweat glands

Answer 33

eccrine - apocrine -

Question 34

types of malignant melanoma

Answer 34

basal cell carcinoma squamous cell carcinoma malignant melanoma

Question 35

basal cell carcinoma

Answer 35

``` basale layer 30% incidence rate slow growth arises from hair follicle treatment: surgical removal ```

Question 36

squamous cell carcinoma

Answer 36

atypical cells of epidermis disruption of basement membrane tumour spread into lymph

Question 37

malignant melanoma

Answer 37

metastatic and invasive | effects melanocytes -> abnormal with dark keratin granules that migrate through epidermis and dermis entering the lymph

Question 38

stages of wound healing

Answer 38

1. Blood clot formation 2. Macrophages remove damaged CT fibres 3. Re-epithelialisation 4. Deposition and remodelling of CT and the CT matrix

Question 39

Eccrine sweat glands: characteristics

Answer 39

- most common - temp regulation - coiled tubular glands - produce sweat - excretes ammonia, urea, uric & lactic acid

Question 40

Apocrine sweat glands: characteristics

Answer 40

- active at puberty - coiled, compound tubular glands - secretes odourless compounds that become odiferous when acted upon bacteria - found in axillae, genitalia

Question 41

sebaceous glands: characteristics

Answer 41

- pheromones - holocrine secretion - oily sebum secretion - empties into hair follicles

Question 42

epithelium: characteristics `

Answer 42

- presence of basement membrane - high cell turnover - defined apical surface - involved in formation of exocrine and endocrine glands