HUBS192 - Lectures 1-3 skin

What are the 7 functions of the skin?

• protect underlying tissues and organs against impact, abrasion, fluid loss and chemical attack

• excrete salts, water and organic wastes

• maintain normal body temp

• produce melanin and keratin

• synthesis vitamin D3

• store lipids in adipocytes in the dermis

• detect touch, pressure, pain and temp and relay the info to the nervous system

what does melanin do?

protects underlying tissue from ultraviolet radiation

what does keratin do?

protects against abrasion and serves as water repellent

what are the 3 layers of the skin? and describe each layer?

1. Epidermis

   • barrier

   • mostly keratinocytes

   • no blood circulation

2. dermis

   • protein fibres for strength

   • vascular

3. hypodermis

   • adipose tissue

What layer of the skin is the subcutaneous layer?

hypodermis

what tissue type is epidermis made of?

epithelial tissue

what two layers is the dermis made of and describe them?

1. papillary layer - consists of highly vasularised tissues (for nourishment)

2. reticular layer - mesh like structure made of collagen and elastin fibres (for strenght)

What are the 2 plexuses of the dermis? describe them

1. cutaneous pelxus

   • network of bood vessels

   • supplies hypodermis, deeper dermis, capillaries for hair follicles and sweat glands

2. subpapillary plexus

   • branches from cutaneous plexus

   • lies deep to the papillary layer of dermis '

   • network of blood vessels for upper dermis and epidermis

What is they hypodermis made of and what is its function?

• adipocytes

• stores energy and provides insulation.

Where is hair found and what is it made of?

all over the body except palms, soles and lips

made of dead keratinized cells

What three things does a hair follicle consist of? describe them

Arrector pilli muscle - contraction that produces goose bumps to improve insulation

root hair plexus - collection of sensory nerves at the base of each hair follicle

Sebaceous glands - produce sebum, naturally moisturises skin and water repellent

what are the two types of sweat glands in the skin? where are they found? what are they important for?

1. eccrine - most areas of the skin - thermoregulation and excretion

2. apocrine - armpit, groin, nipple - influenced by hormones

what is the 3 functions of nails?

• protect fingers / toes

• enhance sensation

• sensory receptors require deformation

what are the signs of aging skin?

• thin dermis and epidermis (reduced collagen)

• slower skin repair

• drier epidermis

• imparied cooling

• less pigmentation

describe the effect tobacco has on skin aging?

• damages collage and elastin

describe the effect vaping has on skin aging?

• nicotine reduces blood ciruclation in the dermis

where is melanin produced? and where are they found?

melanocytes

in the stratum basale

how are melanocytes transferred to epidermal cells? and where are they found?

by melanososmes - throughout the epidermis

what is the difference between a mole and a freckle?

mole - cluster of melanocytes - caused by sun exposure

freckle - melanocytes overprocuding melanososmes

What is vitamin D good for? what does vitamin d deficiency cause?

• essential for calcium metabolism and strong bones

• effects mood

• UV exposure in the skin is required for the synthesis of vitamin d

rickets

What are the two types of skin cancer and describe them

1. basal cell carcinoma

   • common

   • originates in stratum basale

   • metatstasis (spread) is rare

2. malignant melanoma

   • rare but deadly if not treated

   • originated in melanocytes

   • highly metastatic

what layer does a tattoo get inserted into? Why is there so much pain during a tattoo?

dermal layer

dermal layer contains free nerve endings and pain receptors

Describe the process of reducing skin blood flow

• Noradrenaline acts on a1 adrenergic receptors on this vascular smooth muscle in the skin

• GPCRs coupled to intracellualr 2nd messengers = increased intracellualr ca2+ = constriction = reduced skin bloodflow

describe the process of increasing skin blood flow

reducing SNS activation of a1 receptors therefore causes relaxation of arteries to skin —> increases blood flow

Activation of A1 receptors = ?

Reduced activation of A1 receptors = ?

Vasoconstriction

Vasodilation

what are the 4 primary mechanisms of heat transfer?

• radiation

• evaporation

• convection

• conduction

describe the structure and function of eccrine glands

innervated by the SNS

they release Ach

causes sweat when we are hot

what does the preoptic area of the hypothalamus contain?

heat and cold sensitive neurons

describe vasodilation

decrease SNS activation of a1 on skin blood vessels

describe sweating

increase SNS cholinergic activation of mAChRs on sweat glands

what receptors detect temperature below set point?

central thermoreceptors

what are 3 examples of heat generating mechanisms? and describe them

shivering - contractions of agonist and antagonist muscle

non shivering thermogenesis - circulating adrenaline

increased thyroxine - in response to TSH and TRH

How do goosebumps work?

Arrector pilli muscles contracts and pulls the hairs upright. Creates a air bubble and seals the heat so you don’t lose any.

if you have bruns what is a resut of this?

capillaries may leak

What complications can severe bruns lead to?

dehydration

hypothermia

infection / sepsis

renal failure