Breathing System and Excretion
Homeostasis: The maintenance of a constant internal environment, so that living things can function.The Human Breathing System
- Located in the thoracic cavity
- Function is taking in of oxygen and the excretion of carbon dioxide and water vapour
- Nasal Cavity
- Tiny hairs have mucous to filter incoming air
- Moist to humidify incoming air which helps to make gas exchange more efficient
- Buccal Cavity/Mouth
- Most used during exercise due to higher demand
- Air not filtered or humidified
- Epiglotis
- Flaps of tissue at the bottom of the pharynx
- Closes over glottis when swallowing
- Windpipe opening
- Pharynx
- In the throat
- All air passes through here
- Larynx
- Produces sound = voice box
- Vocal cords modulate from air from lungs
- Trachea
- Directs air flow to the lungs
- Rings of cartilage to prevent damage
- Bronchi and Bronchioles
- Bronchi have one to each lung, supported by cartilage
- Bronchioles end in aveoli
- Aveoli
- Air sacks which are the site of gas exchange
Adaptations
- Thin walls
- High blood supply
- Elastic walls which makes exhalation a passive process through relaxing
- Numerous
- Moist; increases efficiency of gas exchange
- Lungs
- Large elastic spongy organs
- Attached and protected by rib cage
- Diaphragm
- Sheet of muscle
- Seals rib cage and separates the breathing system from the abdomen
- Functions in inhalation by moving downwards
- Pleural Membranes
- Covers lungs and is attached to rib cage
- Creates a space = Pleural cavity which is filled with fluid to prevent friction
- Intercostal Muscles
- In between each rib
- Move up and out
- Conscious and unconscious control
- Rib Cage
12 Pairs
- 7 Pairs = True as they are attached to sternum
- 3 Pairs = False as they are only attached by cartilage
- 2 Pairs = Floating as they are not attached
Mechanism of Breathing
Inhalation
- Brain sends signal to Inspiratory Muscles = Intercostal muscles and diaphragm
- Muscles contract
- Volume of thorax increases
- Thoracic air pressure decreases causing air to be pulled in
Exhalation
- Muscles relax
- Elastic tissue of lungs return to original position
- Rib cage moves down and in
- Diaphragm moves up
- Volume of thorax decreases
- Thoracic air pressure increases causing the air to move out
Control of Human Breathing
- Determined by CO2 levels in the blood, too much CO2 would increase the acidity of the blood
- Chemoreceptors sense change in blood pH. If the pH decreases they send signals o the brain to increase breathing rate
Asthma
An inflammation of the bronchi
Symptoms: Wheezy breathing, tightness of chest, shortness of breath
Cause: Pollen/dust/air pollution, exercise
Prevention: Inhalers which open up the bronchioles, avoid allergens
Treatment: Inhalers called bronchodilators
Excretory System in Humans
The Urinary System in Humans
Function of the Kidneys
1) Excretion - Filters the blood
2) Osmoregulation - Controls the filtration and reabsorbtion of water in the blood
3) pH Control - Urine can be slightly acidic/alkaline depending on the blood
4) Hormone Production - Produces erythropoietin which stimulates the production of red blood cells
- Urine passes through the pelvis of the kidney through ureter to the bladder for storage.
Nephron and Associated Blood Supply
Urine Production
1) Filtration
Glomerular Filtrate = water, salts, urea, glucose, amino acids
Adaptations of the Bowman's Capsule
- Cup shaped to hold glomerulus and to increase surface area
- Bowman's capsule wall is one cell thick for easy absorbtion
- Thin projections on the capsules wrap around the capillaries of the glomerulus for more efficient filltration
- Blood flows through glomerulus at high pressure; forces substances out of capillaries
- Capillaries only one cell thick = easy diffusion
2) Reabsorbtion
Proximal Convoluted Tubule Adaptions
- Long and convoluted to increase surface area
- Walls are one cell thick for easy diffusion
- Large blood supply
- Internal wall has microvilli to increase absorbtion
- Reabsorbs all glucose and amino acids through active transport, most water and most salt
Descending loop of Henle
- Reabsorbs some water, calcium and magnesium
Ascending Loop
- Reabsorbs salts
Distal Convoluted Region
- Reabsorbs water, depending on the concentration of Anti-Diuretic Hormone
- Reabsorbs salts
Collecting Duct reabsorbs water base on concentration of ADH
3) Secretion
- Drugs, Urea and Hydrogen ions (to decrease blood acidity)
ADH
- Secreted by the pituitary gland
- Water levels high = Decrease of ADH released
- Water levels low = Increase of ADH released
More water is absorbed as the DCT and collecting duct become more permeable and water is reabsorbed.
The Human Skin
- Functions mainly in protection
Epidermis:Outer layer of the skin
Malpighian Layer: Lower layer of epidermis. Contains melenocyte cells which produce melanin. Where the skin cells originate.
Granular Layer: Cells fill with keratin protein which causes them to die as they lose their nucleus and organelles. Gives skin its strength.
Cornified Layer: Impermeable barrier to pathogens. Dead cells are continually brushed off.
Dermis: Contains collagen and elastin which gives skin its strength and elasticity.
Sweat Glands: For homeostasis. Can excrete urea, salts and water.
Sebaceous Gland: Secretes sebum, which maintains the integrity of the skin. Can cause acne by blocking pores and giving bacteria time to multiply.
Sense Organs: Sends signals of the environment to the central nervous system.
Hair Follicle: Attached to the piloerector muscle, when cold the muscle contracts so that hair stands up on skin and traps a layer of air for warmth.
Adipose Tissue: Stores fat which can be converted into Vit.D by sunlight.
Blood Vessels
- High blood supply to the skin to supply nutrients and take away waste products.
Vasodilation: Vessels widen to allow more blood to the surface of the skin whilst hot so that heat can transfer out of the body.
Vasoconstriction: Vessels thin and less blood passes to the surface of the skin so that heat is stored in the body.
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