W10 The Integumentary System Flashcards
What is the integument?
The integument: outer covering of the body,
* Skin, glands, hair, nails
What are the functions of the integument? (5)
- Protection( Abrasion, UV light, Microorganisms, Water loss)
- Sensation
- Vitamin D production
- Temperature regulation
- Excretion
What are the layers of the skin? (3)
- Epidermis: The surface epithelial
layer- Prevents water loss and abrasion
damage - Dermis: An underlying dense
connective tissue layer- Structural strength - The subcutaneous layer
(hypodermis) – below the dermis - Not really skin
What are the features of the Dermis? (in detail)
- Structural Strength
- Connective tissue fibres:
- Collagen / elastic fibres
- Fibroblast cells
Layers of dermis:
* Papillary layer (superficial)
* Reticular layer (deep)
Dermis: Layers
- Dermis Contains:
- Hair follicles / associated muscles
- Sensory receptors
- Sweat and sebaceous glands
- Blood vessels
- Lymphatic vessels
- All carry out key functions of skin
- Papillary layer
- Fine collagenous and elastic fibers
- Blood vessels: supply epidermis
- Oxygen/nutrients
- Dermal papillae: →increase strength of bond to epidermis
- finger prints
- Reticular layer
- denser, collagenous fibers and elastic fibers
- Collagen & Elastic Fibres = strength / stretchability
- Some key functions: Strength, temperature regulation, nutrients to epidermis
What does the epidermis not have?
Blood vessels- they are supplied by the papillary layer
Dermal growth and repair (for info)
Dermis does NOT continually shed and
regenerate itself
* Wound healing: fibroblasts proliferate
* Collagen fibres (generally)
* Some predominant direction
* cleavage lines
* Surgery : Incision made across the cleavage lines
* →produce considerable scar tissue
* Surgery: Incision made parallel with the lines
* →produce less scar tissue
* Overstretched skin →damage to dermis
* stretch marks / striae
How should incisions be made?
Parallel to cleavage lines, resulting in less gaping, faster healing and less scar tissue
(See picture on ppt slide)
The papillary and reticular layers of the dermis are composed mainly of ____?
Connective tissue
Epidermis Structure
- Avascular
- Layers /strata
- 4/5 layers
- Stratum Lucidum (palms/soles of feet)
- Cells generated in basal layer / stratum basale
- Migrate
- Keratinisation
- waterproof
- Cell Turnover ~ 35 days
Full of keratin at the stratum corneum (so are dead cells)
Mitosis only occurs in the skin in the___?
Stratum basale (the basal layer)
Basal cells undergo mitosis
Cell types in the epidermis
- Basal cells (precursor of
keratinocytes) - Keratinocytes
- Over 90% of cells present in
skin - Contain keratin
- Melanocytes
- pigment-producing cells (5%
of the total) - filter ultraviolet light
- Langerhans cells
- dendritic (branched) - immune
cells - Merkel Cell –sensory
receptor cells (touch)
Epidermis: Cell layers (Strata)
- Stratum germinativum (growth layer):
- Stratum basale and stratum spinosum
- Stratum basale (base layer)—
- Basal cells; only these cells undergo mitosis
- migrate up - become Keratinocytes
- Merkel cell (information); Melanocyte
(protection) - Stratum spinosum (spiny layer)—
- Keratinocytes: held together (desmosomes)
- Strength /flexibility
- Begin to generate keratin and lipid
- Some basal cells: Only v limited cell division
- Langerhans cells (engulf bacteria)
Epidermis: Cell layers (Strata)
- Stratum granulosum (granular layer)—
- Cells –lots of deposits of keratin /
keratohyalin - Granules - grainy
- Superficial cells: begin to degenerate
- Stratum lucidum (clear layer)—
- dead cells
- Cell walls filled with keratin / keratohyalin
- Stratum corneum —
- Dead cells filled with keratin (barrier area)
- 15-30 layers
- Constantly shed
- Cells surrounded by lipids
Stratum corneum
- Stratum corneum (in particular)—
- Keratin/keratohyalin –protect against water
loss - prevents penetration of microbes
- the dehydration of underlying tissues,
- mechanical protection against abrasion for the more delicate, underlying layer
- Drug delivery:
- lipid-soluble substances will diffuse through lipid layers
Ecrine Sweat Glands
Most Common,
* Open directly through sweat pores (true sweat glands)
* Function throughout life
* Secretion: mostly water with a few salts
* Secrete perspiration or sweat;
* eliminate wastes; and cools body
2 types of sweat glands?
Ecrine sweat glands and Apocrine sweat glands
Apocrine Sweat Glands
- Open into hair follicles
- Limited distribution—arm pits/ genitalia
- Limited function in humans
- Begin to function at puberty
- Body odour
Types of glands?
Ecrine
Apocrine
Sebaceous
- Sebaceous glands
- Hair folicle
- Secrete sebum—
- oily substance –lubricant for hair and skin
- prevents excessive water loss from the skin
- Lipid - antifungal activity
Gland secretion and shed skin = Surface film
- Protective barrier formed by mixing of secretions of
sweat and sebaceous glands with sloughed epithelial
cells from skin surface - Functions
- Antibacterial, antifungal activity
- Lubrication
- Hydration of skin surface
- Buffer of caustic irritants
- Blockade of toxic agents
Skin Colour
- Depends on:
- Pigments (melanin, beta carotene)
- Blood (haemoglobin)
- Thickness of stratum corneum
- Melanin
- Group of pigments
- Production
- Produced by melanocytes
- Protects from UV
- protects the DNA of dividing epidermal cells from UV ray damage
- Production Affected by:
- UV
- sun exposure stimulates keratinocytes to secrete chemicals that stimulate melanocytes.
- Hormones
- Genetics
- Melanin produced by Melanocytes:
- Melanin into vesicles called
melanosomes - Phagocytosed by Epithelial cells
(Keratinocytes) - Form Nuclear Cap
- All Keratinocytes can contain melanin,
only the melanocytes produce it.
What produces melanin?
Do keratinocytes have melanin?
Melanocytes
Yes, all keratinocytes can contain melanin but only melanocytes produce it.
What produces melanin?
Do keratinocytes have melanin?
Melanocytes
Yes, all keratinocytes can contain melanin but only melanocytes produce it.
Skin pigmentation
- Differences eg
- Annular erythema
- skin reaction that can be triggered by an
infection or some medicines
Vitamin D production
- UV light converts a form of
cholesterol to cholecalciferol (D3)—
a precursor to vitamin D - Blood transports
precursor/Cholecalciferol to liver and
kidneys, - where vitamin D is produced
- Vitamin D is essential for normal
absorption of calcium and
phosphorous - Essential for bone function
Hair - Assumed knowledge – not tested
*Arises from a hair follicle
*Arrector pili: smooth muscle fibres
* innervated by the sympatheticbranch of the autonomic nervous system
* protection, sensory input, thermoregulation, and communication
Theromoregulation - Assumed knowledge – not tested
During strenuous physical activities the dermal blood vessels dilate and sweat secretion
increases. These mechanisms prevent the body from overheating. In contrast, the dermal
blood vessels constrict to minimize heat loss in response to low temperatures.
Which layer of the skin contains the cells that are constantly shed?
Stratum corneum
What is keratinisation?
What does is protect against?
The concentration of keratin increases.
Keratin is a protein
Protects against loss of water
