Integumentary System - 4b Flashcards
What role does the skin play in thermoregulation?
In high temperatures, the skin produces sweat and dilates capillaries to release heat. In cold temperatures, capillaries constrict, and skin muscles contract to produce heat.
How is the skin a blood reservoir?
The dermis stores about 8–10% of total blood in a resting adult as a reserve.
List three protective functions of the skin.
- Protects against abrasion
- Protects against UV radiation
- Protects against harmful chemicals
What are cutaneous sensations?
Sensory responses like touch, pressure, vibration, and tickling detected by skin receptors.
How does the skin contribute to excretion and absorption?
It excretes waste and absorbs fat-soluble substances like vitamins and certain drugs.
How is vitamin D synthesized in the skin?
UV light activates a precursor in the skin; liver and kidneys then convert it into calcitriol.
What is the main cell type in the epidermis?
Keratinocytes – make up ~90%, produce keratin and lamellar granules.
What do melanocytes do?
Produce melanin to protect cells from UV radiation.
What is the function of Langerhans cells?
They are immune cells that use phagocytosis and alert other immune cells.
Where are Merkel cells located and what do they do?
Found in the deepest layer of the epidermis, they detect touch stimuli.
List the layers of the skin from superficial to deep.
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
- Papillary region (dermis)
- Reticular region (dermis)
- Hypodermis / Subcutaneous layer
What happens in the stratum basale?
Mitosis of keratinocytes occurs here; contains melanocytes and tactile cells.
What is special about the stratum spinosum?
Contains 8–10 layers of keratinocytes with spiny projections for strength and flexibility.
What defines the stratum granulosum?
A transitional layer with keratinocytes undergoing apoptosis and forming waterproofing granules.
Where is the stratum lucidum found?
Only in thick skin (palms and soles), composed of clear, dead keratinocytes.
What is the role of the stratum corneum?
Provides a tough outer layer; made of 25–30 layers of dead cells that constantly shed.
Describe keratinisation.
Keratinocytes move from the stratum basale to the surface, filling with keratin over 4–6 weeks.
What makes the dermis strong and flexible?
It contains collagen and elastic fibres.
What are dermal papillae?
Raised structures in the papillary layer containing capillaries and sensory receptors.
What is found in the reticular region?
Dense connective tissue, blood vessels, nerves, hair follicles, sebaceous and sweat glands.
What are the parts and functions of hair (pili)?
- Shaft
- Root
- Functions: heat retention, protection, and touch sensitivity
What is the structure of nails?
Tightly packed dead keratinised cells forming a nail body, free edge, and nail root.
What do sebaceous glands do?
Produce sebum, keeping skin and hair moisturised and inhibiting bacterial growth.
What are the two types of sudoriferous (sweat) glands?
- Eccrine: Widely distributed, watery sweat, for thermoregulation and waste removal.
- Apocrine: In axilla, groin, areola; milky sweat, active at puberty, emotional/sexual triggers.
