Structure and Function of Skin III Flashcards
What is the Dermo-Epidermal junction?
Interface between epidermis and dermis
What are the roles the Dermo-Epidermal junction plays in epithelial-mesenchymal interaction?
Support, anchorage, growth and differentiation of basal cells
Semi-permeable membrane acting as barrier and filter
Is the epidermis avascular?
Yes
What does failure of the Dermo-Epidermal junction cause?
Slipping and blistering of the skin (e.g Bullous pemphigoid, Epidermolysis bullosa)
What are the layers of the Dermo-Epidermal junction, from most to least superficial?
Basal cells, lamina lucida, lamina densa, sub-lamina densa zone
What is the electron density of the lamina lucida and the lamina densa?
The lamina lucida is electron sparse, the lamina densa is thicker and more electron dense
What cells are found in the dermis?
Fibroblasts, macrophages, mast cells, lymphocytes, Langerhans cells
What do fibroblasts produce?
Collagen and elastin (essentially fibres)
What are some structures found in the dermis?
Muscles, blood vessels, lymphatics, nerves
What causes Bullous pemphigoid?
Antibodies attack and break down the Dermo-Epidermal junction (mostly seen in older patients)
What are some features of blood vessels in the skin?
Supply greater than metabolic needs, vessel walls well supported, horizontal plexuses
What is the direction of flow in blood vessels?
Arteriole, pre-capillary sphincter, arterial, venous capillaries, post capillary venules, collecting venules
What causes angioma (birthmarks)?
Excess vessels in the skin
How are the lymphatic vessels organised in the skin?
Sub-epidermal meshed networks
What is the direction of flow in lymphatics vessels?
From smaller non-contractile vessels to larger contractile lymphatic trunks
What do lymphatic vessels allow?
Continual drainage of plasma proteins, extravasated cells and excess interstitial fluid
How are lymphatic vessels involved in the immune system?
Immune surveillance by circulating lymphocytes and Langerhans cells, channelling of micro-organisms/toxins
How is chronic lymphoedema caused?
Damaged lymphatics (either by obesity or infection)
What are some features of somatic sensory nerves (dermatomes)?
Free nerve endings, special receptors
What are the two kinds of special receptors in somatic sensory nerves?
Pacinian (for pressure) and Meisoners (for vibration) corpuscles
What is neurofibromatosis?
Benign tumour of nerve endings
What does every hair strand have attached to it?
A sebaceous gland and pigment cell
How does pigmentation arise?
From melanocytes above dermal papilla
What is the other name for a hair follicle?
Pilosebaceous unit
What makes up a hair follicle?
Epidermal component plus dermal papilla
Where are specialised keratins located in hair follicles in relation to sebaceous glands?
Adjacent to them
What are the phases of hair growth?
Anagen (growing), Catagen (involuting), Telogen (resting)
What are some hormonal influences of hair growth?
Thyroxine, Androgens
Is the telogen phase asynchronous in humans?
Yes
What is Alopecia areata?
Patchy hair loss (most common type)
What is Hirsutism?
Excess hair growth (can be caused by ovarian cancer)
What type of secretion do sebaceous glands use?
Holocrine secretion (opens into pilary canal)
Where are sebaceous glands found?
Widely distributed-largest gland of face and chest
Are sebaceous glands hormone sensitive?
Yes-quiescent pre-puberty
What do sebaceous glands produce?
Sebum-squalence, wax esters, TG and FFA
What is the function of sebaceous glands?
Control moisture loss and protect from fungal infection
What do Apocrine glands develop as part of?
A pilosebaceous unit
Where are apocrine glands found?
In axillae and perineum (start working in teens)
What hormone do apocrine glands depend on?
Androgen
What do apocrine glands produce?
Oily fluid (odour after bacterial decomposition)
What is the function of apocrine glands?
It’s unknown
Where are eccrine glands found?
Whole skin surface-palms, soles and axillae in particular
What nerves eccrine glands supplied by?
Sympathetic cholinergic nerve supply
What stimulates eccrine glands?
Mental, thermal and gustatory stimulus
What occurs in the ultrafiltration that takes place in eccrine glands?
NaCl and HCO3 reabsorbed (hypotonic fluid), can be >10l per day
What is the function of eccrine glands?
Cools by evaporation and moistens soles/palms to aid grip
