Ch.31 - Excretion Flashcards
What is an ectotherm and an endotherm?
Ectotherms gain or lose heat from/to their external environment.
Endotherms generate their own heat from metabolic reactions.`
Draw a vertical section of the skin.
What does the skin excrete?
The skin excretes water and salt when sweating.
What are the layers of the skin?
The skin is made of the outer epidermis, the inner dermis and the subcutaneous tissues below these layers.
What is found on the outer epidermis of the skin?
At the base is the Malpighian layer, these cells are constantly dividing by mitosis to produce new epidermis cells. These cells may push through the granular layer to form keratin(hair, nails). The build-up of keratin forms a hardened cornified layer.
What is found in the dermis?
The dermis consists of connective tissue called collagen. It contains sweat glands, sebaceous glands, hair follicles, nerve receptors and blood vessels.
What pigment is present in the outer epidermis of the skin?
Melanin is a black pigment produced in the Malpighian layer. It gives colour to our skin, hair and eyes. It increases with exposure to sunlight as it helps protect from the harmful effects of UV radiation.
What is the function of the epidermis and dermis?
The epidermis protects us from physical damage and exposure to pathogens. The dermis protects our internal organs.
What is the function of sebum and vitamin D production?
Sebum keeps our hair moist and flexible and keeps our skin moist. Vitamin D helps absorb calcium in the vitamins.
What does the skin do as body temperature rises?
As body temperature rises, the skin tries to lose heat. Vasodilation occurs (the blood vessels near the skin widen). The hair covering the skin remains flat on the surface. The sweat glands release water onto the skin. The evaporation of the sweat release some of the excess heat from the body.
What does the skin do as body temperature decreases?
As body temperature falls, the skin tries to retain heat. The body fat under the skin is a good insulator. Piloerection occurs (the erector muscles pull the hairs upright). Piloerection traps a layer of air around the skin that will get warm and act as insulation. Vasoconstriction occurs (the blood vessels near the surface of the skin contract). Vasoconstriction will reduce the flow of blood to the skin’s surface. The brain will increase the body’s metabolic rate to create more waste heat. The brain causes shivering for this reason.
