Physiology : Structures

Question 1

Skin Components

Answer 1

Epidermis

Appendages

• nail, hair, glands, mucosae
• (in a scar, appendages NOT present)

Dermo-epidermal junction

Dermis

• connective tissue, less. cellular
• collagen fibres produced by fibroblasts

Sub-cutis.
- Predominantly fat

Question 2

Epidermis

Answer 2

Stratified squamous epithelium

95% epidermis= keratinocytes

Movement from basement membrane

Question 3

Layers of epidermis (4)

Answer 3

Keratin
Granular
Prickle Cell
Basal Layer

Question 4

Other cells present in epidermis (3)

Answer 4

Melanocytes
langerhan Cells
Merkel Cells

Question 5

Regulation of Epidermal Turnover

Answer 5

Balance between cells in/ out

Control by

• growth factors
• cell death
• hormones

Loss of control

• skin cancer
• psoriasis

Question 6

Differentiation of Skin layers

Answer 6

Keratinocytes migrate from basement membrane

Continuous regeneration of epidermis

28 days from top to bottom

Question 7

Basal Layer

Answer 7

Usually 1 cell thick
Small cuboidal
Lots of intermediate filaments (keratin)
Highly metabolically active

First layer of epidermis above dermis

Question 8

Prickle Cell Layer

Answer 8

Large polyhedral cells
Lots of desmosomes (connections)
Intermediate filaments connect to desmosomes

Question 9

Granular Layer

Answer 9

2-3 layers of flatter cells

Large keratohyalin granules: contain structural fillagrin and onvolucrin proteins

Odland bodies (lamellar bodies)
High lipid content
Cell nuclei lost

Question 10

Fillagrin

Answer 10

Proteins that are broken down (proteolyzed0 by proteases.

Broken down components of fillagrin retain water

Question 11

Keratin Layer

Answer 11

Tight waterproof barrier

Corneocytes (overlapping non-nucleated cell remnants)

Insoluble cornfield envelope

80% keratin and fillagrin

Lamellar granules release lipid

Question 12

Muscosal membranes

Answer 12

Highly specialised for function

-eyes, mouth, nose, genitourinary, GI

Question 13

Oral mucosa

Answer 13

Masticatory
- keratinised (deal with friction/ pressure)

Lining
- non-keratinised

Specialised
-tongue papillae (taste0

Question 14

Ocular mucosa

Answer 14

Lacrimal glands, eye lashes, sebaceous glands

Question 15

Melanocytes

Answer 15

Migrate from neural crest to the epidermis in first 3 months of foetal development

Basal layer and above

Pigment producing dendritic cells

Question 16

Melanocytes function and structure

Answer 16

Contain organelles: melanosomes

Convert tyrosine to melanin pigment
Melanin absorbs light (neutral density filter)

Full melanosomes transferred to adjacent keratinocyte via dendrites. Form protective cap over nucleus

Question 17

Langerhan Cells

Answer 17

Mesenchymal Origin: bone marrow

Prickle cell level in epidermis
Also found in dermis and lymph node

involved in skin immune system

• antigen presenting cells
• pick up antigen in skin and circulate to lymph nodes via lymphatic system

Question 18

Merkel Cells

Answer 18

Found in basal layer
Between keratinocytes and nerve fibres
Mechanoreceptors

(Merkel cell cancer is very rare. and caused by a viral infection. High mortality).

Question 19

Hair follicles

Answer 19

–> Pilosebaceous Unit

Epidermal component plus dermal papilla
Specialised keratins
Adjacent sebaceous glands
Hair pigmentation via melanocytes above dermal papilla

Question 20

Ceramides

Answer 20

Sebus greasy wax

Question 21

Hair growth

Answer 21

Anagen= growing 
Catagen= involuting (still embedded, not growing) 
Telogen= resting 

regional variations in growth patterns

Hormonal influences : Thyroxine, androgens.

Types: Lanugo (in utero), velds and terminal

Question 22

Nails

Answer 22

Specialised keratins
Largest skin appendage

Matrix epithelium: responsible for production of nail plate

nail bed epithelium: mediates firm attachment

Hypochondrium: seals the sublingual space and allows the nail plate to physiologically detach from nail bed

Question 23

Dermo-epidermal junction

Answer 23

Interface between dermis and epidermis

Key role in epithelial-mesenchymal interactions

• support, anchorage, adhesion, growth and differentiation of basal cells
• semi permeable membrane acting as barrier and filter

Question 24

Conditions related to dermo-epidermal junction

Answer 24

Bullous Pemphigoid

Epidermolysis Bullosa

Question 25

Bullous pemphigoid

Answer 25

Chronic itchy blistering disorder Autoimmune disease Destroyed derma-epidermal junction

Question 26

Epidermolysis Bullosa

Answer 26

Blistering of skin and mucous membrane that occurs secondary to minor trauma Rare Due to various abnormalities in proteins in derma-epidermal junction

Question 27

Dermis

Answer 27

Ground substance (supportive and. water based) Cells, fibres, muscles, blood vessels, lymphatics and nerves

Question 28

Dermis cells and fibres

Answer 28

Cells - Fibroblast - Macrophages - Mast cells - Lymphocytes - Langerhan cells Fibres - Collagen (mainly) - Elastin

Question 29

Dermic Blood Vessels

Answer 29

Supply greater than metabolic need Vessel walls well supported by collagen and muscle fibres Horizontal plexuses - Superficial vascular plexus - Deep vascular plexus

Question 30

Dermis Blood Vessel Flow

Answer 30

1. Arteriole 2. Precapillary sphincter 3. Arterial 4. Venous capillaries 5. Post capillary venues 6. Collecting venues

Question 31

Angioma

Answer 31

benign tumour composed of blood/ lymph vessels

Question 32

Dermis Lymphatic Vessels

Answer 32

Sib-epidermal meshes networks Smaller non-contractile venues --> larger contractile lymphatic trunks Continual drainage of plasma proteins, extravasated cells and excess interstitial fluid Immune surveillance by circulating lymphocytes and langerhan cells, Channeling of micro-organisms/ toxin

Question 33

Chronic lymphoedema

Answer 33

Thickened, cobblestone skin | Will NOT be pitting

Question 34

Dermis Nerves

Answer 34

Somatic Sensory (dermatomes) - free nerve ending - special receptors - -> Pacinian (pressure) - -> Meissners ( vibration) Autonomic nerve supply - Blood vessels, nerve, glands

Question 35

Dermis hair Follicles

Answer 35

Pilosebaceous Unit Epidermal component plus dermal papilla Specialised keratins: adjacent sebaceous glands Pigmentation: melanocytes above dermal papilla

Question 36

Skin glands

Answer 36

Sebaceous Glands Apocrine Sweat Glands Eccrine Sweat Glands

Question 37

Sebaceous Glands

Answer 37

Most superficial gland Holocrine secretion opening into hilary canal Widely distributed (largest glands of face and chest) Hormone sensitive Produce sebum (squalene, wax, esters, TG and FFA) Control moisture loss Protection from fungal infection Acne results from clogging of glands

Question 38

Apocrine Sweat Glands

Answer 38

Develop as part of pilosebaceous unit Axillae and perineum Androgen dependent Produce oily fluid - odour after bacterial decomposition

Question 39

Eccrine Sweat glands

Answer 39

Whole skin surface Sympathetic cholinergic nerve supply Ultrafiltration (can be >10l per days) Cooling by evaporation Moistens palms/ soles to grip