Structure & Function of Skin Flashcards
What kind of tissue makes up the epidermis?
Stratified keratinising squamous epithelium
What kind of tissue makes up the epidermis?
Connective tissue
From which germ layer does the epidermis come from?
Ectoderm (which form a single layer periderm)
From which germ layer does the dermis come from?
Mesoderm
In early foetal development, what has developed of the skin at 4 weeks, 16 weeks and 26 weeks?
4 weeks: 3 layers - Periderm, basal layer and dermis
16 weeks: Final layers have formed
26 weeks: Skin appendages develop
Blaschko’s Lines
Developmental growth pattern of skin (not following vessels, nerves or lymphatics)
What kind of epithelium is the epidermis?
Stratified squamous epithelium
Which type of cells make up the majority of the epidermis?
Keratinocytes
What are the epidermal skin layers?
1) Keratin layer
2) Granular layer
3) Prickle cell layer
4) Basal layer
Where do the keratinocytes come from?
Basement membrane then migrate
What are hallmarks of the granular layer?
Odland bodies
Which granules are found in the granular layer?
Keratohyalin granules containing filaggrin and involucrin proteins
Which cells make up the keratin layer (stratum corneum)?
Corneocytes - overlapping non-nucleated cell remnants (dead cells) connected by lipids (essentially a wax) forming an insoluble cornfield envelope
What is the function of keratinocytes?
Production of keratin in order to form a barrier against environmental damage by pathogens, heat and water loss
How do melanocytes create pigment in order to protect from UV?
Convert tyrosine to melanin which absorbs light.
What are melanosomes and how are they transferred?
Small sacs for melanin and transferred between adjacent keratinocytes via dendrites.
What is the function of Langerhans’s cells and where are they found?
Present at the prickle cell level in epidermis, as well as the dermis and lymph nodes.
They are involved in the skin immune system acting as antigen presenting cells
What is the function of Merkel cells and where are they found?
Mechanoreceptors found in the basal layer between keratinocytes and nerve fibres
What are hair follicles also known as?
Pilosebacous units (as they are always next to a sebaceous gland)
What are the 3 phases of growth in hair follicles?
1) Anlagen (growing)
2) Catalan (involuting)
3) Telogen (resting)
What is lanugo hair?
First hair produced by the follicles in utero at around 5 months. Very fine, sort and unpigmented
What is vellus hair?
Fine, short, light-colored or transluscent, and non-pigmented that develop from childhood and are found on most areas of the body.
What is terminal hair?
Thick, long, and dark hair which replaces vellus hair during puberty in response to androgens in certain parts of the body
Telogen effluvium
When the telogen phase becomes synchronous and lots of hair enters the shedding phase at once
What are the components of a pilosebacous unit?
What are the components of a nail?
What are the growth patterns of a nail?
Nail proliferates in the matrix then grows out and forms the layers of the nail plate
What are the 2 layers of the derma-epidermal junction (DEJ)?
Lamina lucida and lamina densa
What are the 2 main components of the dermis?
Fibroblasts and their elastic fibres (type I and III collagen), and ground substance
What are the 3 types of glands found in the skin?
Sebaceous, apocrine and eccrine glands
Which glands enlarge at puberty and are associated with acne?
Sebaceous glands
What do sebaceous glands produce?
Sebum (squalene, wax extras, triglycerides and free fatty acids)
What actually is acne?
A mixture of increased sebum, blocked ducts and bacterial activity
Which glands are found in the axillae and perineum and are scent glands?
Apocrine
Which glands have a sympathetic cholinergic nerve apply and are therefore association with mental, thermal and gustatory stimulation?
Eccrine
What is the function of eccrine glands?
Cooling by evaporation and moistening palms and soles to increase grip
Which glands are associated with androgens?
Sebaceous and apocrine
What metabolism is the skin involved in?
Vit D metabolism (using UV) and thyroid hormone metabolism
**Which 4 sensory receptors are found in the skin?
Merkel’s, Meissener’s, Ruffini’s and Pacinian (all the lads)
What are the layers of the skin?
Epidermis > Dermis > Superficial fascia > Deep fascia
What are the components of the superficial fascia?
Loose connective tissue, fat and vessels
What are the components of the deep fascia?
Dense connective tissue
Fascia Lata
Flat sheet of dense connective tissue in the deep fascia surrounding muscles (forms the compartments)
What is the series of arteries supplying the upper limb?
Subclavian > Axillary > Brachial > Radial and Ulnar > Superficial and deep palmar arch
What does the ulnar a. go on to form?
The superficial palmar arch, which anastomoses with the radial a.
What does the radial a. go on to form?
The deep palmar arch, which anastomoses with the ulnar a.
Where do the veins in the hand tend to drain to?
The dorsal surface of the hand forming the dorsal venous network
What is the venous drainage of the upper limb?
- Superficial: Basilic and cephalic v. (joined by the median cubital v.)
- Deep: Radial and ulnar > Brachial v.
- The brachial and basilar then join > axillary (joined by the cephalic) > subclavian v.
What is the arterial supply of the lower limb?
- Femoral > Popliteal
- > Anterior tibial: ( > dorsal pedis > arcuate a.)
- > Posterior tibial (> fibular, medial plantar and lateral plantar > plantar arch)
What is the venous drainage of the lower limb?
Small saphenous > popliteal > femoral and then joined by great saphenous > external iliac v.
What kind of arteries are digital arteries, and what shouldn’t be given to these kind of arteries?
End arteries; adrenaline-containing local anaesthetics
In the limbs, what do lymphatics generally follow?
Veins
In the abdomen, what do lymphatics generally follow?
Arteries
Langer’s Lines
Lines of tension in the skin (incisions should aim to follow these lines, and not cut across them)
What is there epidermal basement membrane made of?
Laminin and Type IV collagen
What is the embryogenesis of melanocytes?
Derive from the neural crest, then the melanoblasts migrate from the neural crest to skin, uveal tact and leptomeninges. When they settle in the skin they become melanocytes.
Where do melanocytes originate from?
Neural crest (which is why they have similarities to neurons)
