UNIT 04 RESPIRATION AND EXCRETION Biology 3º ESO Macarena Arechavaleta 1.Respiratory system Every cell in our body needs oxygen (O2) to obtain energy. Cellular respiration (reaction of glucose/fatty acids with O2) generates H2O and CO2. 1.The human respiratory system CO2 must be eliminated from cells and expelled from body. The respiratory system takes oxigen from the air and transfers it to the blood stream, while taking carbon dioxide from the blood and expelling it from the body. Is divided in two parts: The respiratry tract The lungs 1.1.The respiratory tract Group of tubes that carry air from outside the body into the lungs and Pharynx Nasal cavities viceversa. Larynx Consist of: Trachea Bronchi Lungs diaphragm 1.1.The respiratory tract: bronchi • The bronchi are two tubes, each one leads to a lung. • The bronchi split into gradually narrower tubes inside the lungs: the bronchioles. • The bronchioles end in a small hollow cavities called alveoli, tiny sacs with very thin walls surrounded by a network of capillaries. • Alveoli are the site of gas exchange with the blood. • Each lung contains ≈ 300 million alveoli. 1.2. Lungs • Two organs formed of spongy tissue. The right one has three lobes, left one two (leaves room for heart) • They are inside the chest cavity, (separated from the abdominal cavity by the diaphragm) protected by the ribs and surrounded by a double membrane: the pleura. • The pleura is full of pleural fluid, liquid that protects the lungs from rubbing against the ribs and facilitates the movements involved in breathing. Pleural membranes Pleural fluid Lungs Ribs Lung Diaphragm 1.3.How the respiratory system works Three stages to breathing: 1) Inhalation (or inspiration) 2) Gas Exchange 3) Exhalation (or expiration) • Air from the atmosphere enters into the lungs. • Active process: the diaphragm contracts to expand the chest cavity. The lungs expands. Pulmonary ventilation: Inhalation • Air enters through mouth or nasal cavities where it is heated before travelling through the respiratory tract to the alveoli. • Healthy adults inhale around 18 times per minute (in calm) • Gases move by simple diffusion: they pass through cell membranes, moving from where they are most concentrated, to where there is least concentration. • O2 which is highly concentrated in the alveoli (inhalation) passes trough Gas exchange the thin walls into the incoming blood (which is low on O2). • The abundant CO2 in this blood coming from cellular metabolism from the rest of the body diffuses into the inside of the alveoli (where there is little CO2) and is expelled (exhalation). • Veins and arteries are defined depending on if they go to or come from the heart. Therefore, arteries bring CO2 to the lungs and veins take O2 rich blood to the heart. Gas exchange: O2 transfers from the air to the blood, CO2 transfers from the blood to the air. • Air is pushed out of the lungs. • Passive process: The diaphragm relaxes so the chest cavity decreases and the lungs reduce in volume. Pulmonary ventilation: Exhalation • This ensures the air the lungs contain which is loaded with CO2 is expelled through the respiratory tract. Infectious diseases 1.4. Diseases that affect the respiratory system Microorganisms colonising and destroying mucus membranes Sinusitis Tonsilitis Pharyngitis Pneumo-thorax Air enters pleural space around the lungs Lung colapses Inflammatory diseases and allergies Lip, tongue, throat and lung cancer Allergic rhinitis Main cause is cigarette smoke Asthma Abnormally growing cells invade and destroy surrounding tissue Chronic bronchitis Bronchitis Bronchiolitis Pneumonia Pulmonary emphysema If cells detach and wander through the system cancer can spread Hypoxia is not a disease but a condition. For various reasons the oxygen concentration in the blood can be too low.Can cause severe brain damage and even death. Possible reasons are an obstructed umbilical cord at birth, being at high altitude or obstructions in or inflammation of the respiratory system 2.Excretory system • Excretion is the elimination of waste products which result from the metabolic activity of cells. • Without excretion, the waste products would accumulate and 2. The excretory system become toxic. • Excretion is carried out by 1. Urinary system 2. Respiratory system 3. Sweat glands 4. Liver 2.1.Urinary system Consists of: • Kidneys • Ureters • Urinary bladder • Urethra Two bean-shaped organs ≈10-12 cm. One on either side of the spinal column Surrounded by a thick layer of fat. Kidneys The kidneys are formed by structures called nephrons, which produce urine. Each kidney has an adrenal gland on top, part of the endocrine system. The renal artery enters the kidney on its concave side. The renal vein and ureter also exit the kidney on this side. Cortex: rough outer layer Kidneys Renal vein Medulla: middle layer, splits into renal pyramids Renal artery ureter Renal pelvis: innermost part. Funnel-shaped, connected to ureter. 2.2. Nephrons • Structural units that filter the blood and produce urine. • 1.000.000 per kidney approx. • Consists of the following parts: • Bowman’s capsule (1): Water, waste and other substances are filtered out from blood. • Proximal convoluted tubule (2) • Tubule and loop of Henle (3): water, glucose, amino acids and mineral salts are returned to blood. • Distal convoluted tubule (4) • Collecting tubule (5): Remaining liquid is called urine, flows to renal pelvis. COMPOSITION • 95% of urine is water. • 3% is made up of toxic substances, such as urea and uric acid. Urine • 2% is made up of mineral salts, mainly sodium and potassium. FUNCTIONS • Eliminate toxic waste from the body. • Regulate the levels of ions in the blood. • Balance fluid levels. • Regulate blood volume and pressure. Urine production FILTRATION REABSORPTION SECRETION Urine production 1. FILTRATION: Liquid passes from the blood in the glomerulus into the Bowman´s capsule. This process filters out water, waste products and other substances such as vitamins and glucosa. 2. REABSORPTION: Substances such as water, glucosa, aminoacids and mineral salts are returned to the blood from the tubules and loop of Henle. 3. SECRETION: Some substances, such as potassium ions, pass from the body fluids into the final part of the nephron. Urine is produces and flows to the renal pelvis. From the renal pelvis, urine passes through the ureters to the urinary bladder, where it collects. URETERS Two 25 cm-long, narrow tubes. They take urine from the kidneys to the urinary bladder. URINARY BLADDER Expandable, muscular organ. Collects up to 0,5 L of urine, (although it can store up to 2 L). Urine flows continuously from the ureters into the bladder. When the bladder is full, urination occurs. URETHRA Urine flows through this tube from the bladder to the outside of the body during urination. The process of urination is controlled by two small muscles called sphincters at the top and bottom of the urethra. Lungs Expel CO2 carbon dioxide produces by cell metabolism. Liver 2.3.Other excretory organs Eliminates bilirubin from hemoglobin breakdown and other toxic substances and medicine. Elimination occurs through bile which flows into small intestine and is excreted when defecating. Sweat glands Made up of glomerulus (a twisted portion in dermis) and a duct ending in a pore. Consists of water (95%), mineral salts, urea, uric acid, lactic acid and potassium. Important for regulating body temperature. 2.4. Excretory system health Kidney disease – stop filtering blood so the blood is not purified. Treated with dialysis or kidney transplant. Urinary system diseases Kidney stones – solid structures formed of uric acid and calcium salts. Cystitis – inflammation of urinary bladder, often caused by bacteria.
