What is integumentary system?
A tough, protective layer
Eg. Skin, hair and nails
What is the order of layers in the skin?
Top= epidermis
Middle= dermis
Bottom= hypodermis
What is another name for the hypodermis?
The subcutaneous layer
Superficial fascia
What does the hypoderm originate from?
Mesoderm
How thick is the hypodermis?
Varies in thickness in different areas of the body / different people
Eg. Thin in eyelids, thick in backside
What is the hypodermis made of?
Mainly adipose tissue
Some lymph nodes
What type of tissue is the hypodermis?
Loose connective tissue- fibroblasts, macrophages, fibres
What are the functions of the hypodermis?
Provides energy store
Generator of heat- brown adipose (neck, kidneys etc)
Insulator
Shock absorber (hands & feet)
Connects dermis to underlying muscle and bones
Smooth movement- allows skin to move smoothly over underlying structures
Source of peptide hormone leptin (made in white adipose)
What is the effect of the hypodermis thinning during ageing?
Skin wrinkling
Hypothermia in old age
What type of connective tissue is the dermis?
Dense irregular connective tissue
What is a pilosebaceous unit made up of, and where is it found?
Found in the dermis:
Arrector pili muscle
Sebaceous gland
Hair follicle
What does the dermis originate from?
Ectoderm
How thick is the dermis?
Variable thickness
Thin in eyelids, thicker in hands/feet
What is the structure of the dermis?
Made of two layers:
-Papillary - upper
-Reticular - lower
+ Dermal papillae
What is dermal papillae?
Interdigitating - projections that link epidermis and dermis together so they don’t slide over each other (allow them to stay in place)
Cause fingerprints and toe prints (in utero influence)
What are the functions of the dermis?
Thermoregulation- hair and sweat glands
Sensory (touch)
Contains fibroblasts, histiocytes (tissue macrophages), mast cells and dermal adipocytes
Contains nerves, blood vessels, lymphatics ams cutaneous appendages (pilosebaceous units) [eccrine- all over body; apocrine- attached to hair follicles (armpits & perineal area)]
Gripping objects- sweat gland
How does thinning of the dermis lead to skin wrinkling during ageing?
Loss of collagen and elastin fibres
What tissue type is the epidermis?
Keratinised stratified squamous epithelium
