The Excretory System Flashcards
Ectotherms
Gain or lose heat from or to their external environment
Fish, snakes, lizards
Endotherms
Generate their own heat from metabolic reactions
Metabolism is independent of the external environment
Mammals
Name the skin layers
Outer epidermis and inner dermis and adipose tissue
Layers of epidermis are called
Cornified, granular and Malpighian layers
Cornified layer consists of ___ skin cells
Dead
Skin cells contain the protein
Keratin which makes hardened, tough and waterproof
Malpighian layer contain ____ cells
Living cells
Actively dividing by mitosis to produce new epidermal cells
Cells in the malpighian layer produce the pigment
Melanin which is a brown or black pigment that gives the skin, nails, hair its colour
The Dermis is a layer which is found below the epidermis. It consists of:
Live connective tissue which contain elastic and collagen fibres to give skin its elasticity
It also contains Blood vessels Various receptors Hair follicles Sweat glands
Role of adipose tissue
Insulate the body and act as food storage
6 functions of skin
Formation of vitamin D in UV light Energy store Sense organ Immunity Excretory role Temperature regulation
Formation of Vit D in the presence of UV light. What is vit D needed for? What is a lack in vit D result in?
Essential for the absorption of calcium and phosphorous from the small intestine
Lack = rickets - bones become soft and this results in bowed legs
Skin as an energy store. What is the tissue called below the dermis? What does it store?
Adipose tissue, stores energy as fat
Skin as a sense organ, what does the skin contain
Numerous receptors which detect stimuli such as touch, pressure, cold and warmth
Skin - immunity - general defence system role
Skin acts as a physical barrier to prevent pathogens and many toxins entering
Shedding of the cornified layer helps remove pathogens
Oily sebum is antibacterial and moisturises and waterproofs the skin, preventing cracking of the skin and pathogens entering
Sweat - lysozyme causes lysis of pathogen cells
Skin - excretory role - what is excreted through the skin?
Sweat - secreted by the sweat glands, through the sweat duct on to the skin epidermis
Sweat helps to excrete excess water, salts and urea.
Temp regulation by the skin. Core body temp is __ degrees
37 degrees - maintains high metabolism and prevents enzyme denaturisation.
3 body responses to a rise in body temperature
1) increased sweating - evaporation of sweat removing heat so body cools down
2) arterioles dilate (vasodilation)
Increased blood flow to the blood capillaries in the dermis layer cause heat to radiate away from skin surface
3) hair lies flatter- layer of trapped air is thinner, giving less heat insulation so heat is lost quickly
4 responses to a drop in body temp
1) arterioles constrict - vasoconstriction
Keeps in body heat as the flow of warm blood close to skin surface is reduced
2) hairs stand erect - traps a layer of warm air, heat insulation
3) shivering ( involuntary skeletal muscle activity) increases heat production
4) increased thyroxine levels speed up metabolic rate, generating heat.
Definition of excretion
The elimination of metabolic waste from the body : CO2, water, urea, salts
Homeostasis
The ability of an organism to maintain a constant internal environment
