1001NSC Lecture Notes - Lecture 3: Apocrine, Arrector Pili Muscle, Tyrosinase
20 Jun 2018
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Week 3 - 17th March
Module 2: The Integumentary System
The skin and associated structures
Skin: largest organ of the body, many thick layers, sweat and oil glands, hair follicles, nail,
specialised nerve endings (sense of touch)
A physical and chemical barrier (for protection)
Maintains body temperature (via perspiration, negative feedback)
Enables the body to sense the environment (receptors for pain, tuch, temp, pressure,
vibration)
Vitamin D synthesis (UV_B light penetrates blood in skin, converts cholesterol derivatives
to inactive vitamin D, carried to kidneys via blood, becomes activated and is utilised to
maintain bones, teeth etc)
1-2% of oxygen we take in is diffused through the skin
3 layers of skin: epidermis (flattened epithelium tissue)
dermis: (connective tissue, glands, blood, lymph vessels, nervous tissues)
hypodermis: (adipose tissue, “fatty layer”)
Epidermis:
Keratinocytes: contain fibrous intermediate filament protein (keratin)
Melanocytes: decrete pigment (melanin)
Langerhans’ cells (Anti-Presenting Cells: APC): immune surveillance, present antigens
(foreign particles)
LEARN LAYERS. THEY ARE IN TEST
Layers of the epidermis:
Stratum comeum: dry, hard layer, dead cells. 75% of epidermis
Stratum lucidum: clear, protein layer (only palms of hands, soles of feet. areas of most ware and
tear, most use)
Stratum granulosum: granular layer. Keratohyaline granules/glycolipid
Stratum spinosum: spiny layer. Developed desmosomes
Stratum basale: (germinativum) innermost base. New cell proliferation
New epidermis every 25-45 days. We shed every 25-45 days
Clinical Disorders
Ichthyosis: The skin resembles the scales on a fish. 28 varieties of the skin disorder. Very hard,
dry, scaly skin. Too much keratin so the epidermis is thickened and cracked
Melanocytes: this pigment forms a shield over the skin cell, the UV light cannot penetrate this and
change the DNA. Different embryonic origin to kerinocytes (different type of cell). 10-25% of the
cells in stratum basale are melanocytes
Melanin pigment: comes from amino acid in our diet called tyrosine. The melanocytes deliver
melanin granules to kerinocytes
Brown pigment on melanocytes secrete melanin
If UV gets last melanin shield (too much sunburn), it leads to major DNA damage, possibly cancer
All humans are prone to melanoma, not just fair-skinned people
The UV light gets past the shield and “thymine dimers” form a “speed bump” in the DNA
Refer to Thymine Dimers pic
Light-photoreacting exam breaks off the speed bump and fixes the burn
Types of skin cancers:
Basal cell carcinoma (most common and easiest to treat)
Squamous cell carcinoma (2nd most common)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Skin: largest organ of the body, many thick layers, sweat and oil glands, hair follicles, nail, specialised nerve endings (sense of touch) Enables the body to sense the environment (receptors for pain, tuch, temp, pressure, vibration) Vitamin d synthesis (uv_b light penetrates blood in skin, converts cholesterol derivatives to inactive vitamin d, carried to kidneys via blood, becomes activated and is utilised to maintain bones, teeth etc) 1-2% of oxygen we take in is diffused through the skin. 3 layers of skin: epidermis ( attened epithelium tissue) dermis: (connective tissue, glands, blood, lymph vessels, nervous tissues) hypodermis: (adipose tissue, fatty layer ) Langerhans" cells (anti-presenting cells: apc): immune surveillance, present antigens (foreign particles) Stratum lucidum: clear, protein layer (only palms of hands, soles of feet. areas of most ware and tear, most use) Ichthyosis: the skin resembles the scales on a sh. Too much keratin so the epidermis is thickened and cracked.
