Anatomy - Skin - Dermis, Hypodermis, Thickness and Color

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Dermis, Hypodermis, Thickness and Color

Dermis

- second layer of skin
- consists of dense connective tissue

Function of dermis

- nourish epidermis via vast network of blood capillaries and vessels
- form supporting framework composed of collagen (strength) and elastin (elasticity)

List the 7 structures of the dermis

- blood capillaries
- lymph vessels
- sensory nerve endings
- arrectores pilorum muscle
- sweat glands and ducts
- sebaceous glands
- hair follicles

List the 2 layers of the dermis

- papillary layer
- reticular layer

Papillary Layer

outer layer of the dermis, directly beneath the epidermis, consists of many papillae

Reticular Layer

deeper layer of the dermis, consists mainly of bands of strong, white, fibrous collagen fibers and some yellow elastic fibers

Dermal Papilla

- fingerlike projection of the papillary region of the dermis
- consists of fine fibril tissue and a few elastic fibers, some may contain tactile nerve endings

List functions of dermal papillae

- on palms and soles, papillae are arranged in parallel lines to form a person's fingerprints
- protect against continuous friction
- help prevent slippage (when holding an object or walking)

Functions of blood vessels of the dermis

- arterioles supply sweat glands, sebaceous glands, hair follicles and the dermis with oxygen and nutrients
- deoxygenated blood is carried away by venules
- temperature regulation
- clot building when skin is cut to prevent further escape of flood and bacteria entering the body

Function of lymph vessels in the dermis

- drain away waste particles that are too large for veins to carry

Hair Follicles

- formed by down-growth of epidermal cells into the dermis
- tube like pockets of epidermal cells that make hair cells and external keratin
- exists of bulb, root and shaft

Arrector Pili Muscle

Tiny smooth involuntary muscle, attached to hair follicle and contracts when cold or frightened and produces goosebumps.

sensory nerve endings in the dermis

sensitive to touch, pressure, pain, heat and cold, conveying nerve impulses to the CNS

Sweat glands

tubular structures that produce sweat

Sebaceous glands

microscopic glands that secrete sebum, an oily/waxy matter that lubricates and waterproofs the skin and hair

Hypodermis

- deepest layer of the skin
- formed from loose connective tissue, separating upper layers of skin from underlying muscle tissue
- permits skin to move easily over muscle
- contains blood and lymph vessels, nerves and fat cells

Which factors affect skin thickness

- area of the body: skin is thinnest on eye-lids and thickest on the palms and soles
- age: skin becomes thinner as one ages
- environmental exposure: UV exposure makes skin thicker
- oil content: more oily skin is thicker than dryer skin
- medication: e.g. cortisone results in thinning of skin

Which factors affect skin color

- skin thickness
- blood vessels and flow
- melanocytes and melanin
- carotene

Name 5 pigments that affect skin color and give their color and location

Pigment Color Location
Haemoglobin purple part of red blood cells
Oxyhaemoglobin red part of red blood cells
Melanin brown stratum germinativum
Melanoid brown throughout epidermis
Carotene yellow/orange stratum corneum, adipose cells

Which nutrients are necessary for the production of collagen?

Collagen is a protein and amino acids are the building blocks for proteins. The production of collagen therefore requires various nutrients that enhance the production of the amino acids alanine, lysine, glycine, proline and hydroxyproline. Major protein sources in a healthy diet include lean meat, fish, dairy products, legumes, nuts and seeds. Other nutrients for collagen production include Vitamin C, iron, manganese and Vitamin D.

Langer's Lines

also called cleavage lines, bundles of fibers in reticular layer of dermis, if surgery is performed along these lines only a fine scar is usually left

Cells of the dermis

fibroplasts, mast cells and histiocytes

Fibers of the dermis

elastin and collagen

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