The skin

The dermis and appendages The subcutaneous layer Functions of the skin

The dermisWhere is the dermis located?

It is located beneath the epidermis and above the subcutaneous layer

It is the largest layer, and varies from 1.5 mm to 4 mm in thickness

What are the functions of the dermis?

The main functions of the dermis are to regulate temperature, and to protect, support and nourish the skin.

Much of the bodys water supply is stored within the dermis

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What is the structure of the dermis?It is composed of two layers of areolar connective tissue and contains:

Sensory receptors/nerve endingsSweat glands: - Eccrine:found all over the body - Apocrine: found in the groin and axillae

Sebaceous glandsHair follicles/hair shaft/hair bulbArrector pili muscleBlood and lymphatic vessels

Handout 17

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The dermis consists of two layers:1. 1. The papillary layer2. 2. The reticular layer

The papillary layerThe upper, papillary layer, contains small cone–shaped projections called papillae, which contain looped blood capillaries carrying blood and lymph.

There are also tactile corpuscles and nerve endings.

The papillary layer supplies nutrients to the epidermis and regulates temperature.

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The reticular layerThe lower, reticular layer, is thicker and contains fibroblast cells, which are responsible for the formation of collagen fibres and elastin.

Yellow elastin fibres give the skin its flexibility and elasticity. White collagen fibres plump the skin and give strength and firmness.

Specialised cells are also found in the reticular layer:Macrophages destroy bacteria and tissue debrisMast cells secrete histamine, which causes vasodilation, and heparin, which stops blood clotting (anti-coagulant).

The reticular layer supports other components of the skin, such as hair follicles, sweat glands, and sebaceous glands.

Handout 17

Nerve endings of the dermis Meissner's corpuscles are for light touch and lie immediately

beneath the basement membrane of the epidermis

Pacinian corpuscles are for deep pressure, and lie deeper in the dermis

Free nerve endings are for pain and temperature, and these endings lie at the superficial aspect of the dermis

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Subcutaneous layer (hypodermis)The deepest layer lying directly above the muscles of the body and below the dermis of the skin.

It is made up of two main types of connective tissue:

Adipose tissue forms a network of fat cells providing the body with insulation, as well as acting as a source of energy

Areolar tissue gives strength to protect underlying structures. Elasticity to cope with increases in size, and support for blood vessels and nerve endings found in this layer

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Learner activityLabel the cross section diagram of the skin

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Arrector Pili muscle

Sweat Duct

Sensory Nerve Endings

Hair shaft

Adipose Tissue

Subcutaneous Layer

Dermis

Epidermis

Sweat gland

Blood & Lymph Vessels

Nerve

Sebaceous gland

Hair Follicle

Muscle

Functions of the skin• SECRETION• HEAT REGULATION• ABSORPTION• PROTECTION• EXCRETION• NUTRITION – Production of Vitamin D• SENSATION

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Any questions?