Presentation on theme: "The Urinary System Excretion: The removal of metabolic wastes from the"— Presentation transcript:
1 The Urinary System Excretion: The removal of metabolic wastes from the body as a result of cellularactivities
2 Examples of Excretion: Skin – Excretes sweat (a solution of water, salt, and some urea)- Used to cool the body than secretion of wastes.- Increase in wastes during times of renal failure (kidney)Liver – Breaks down old red blood cells- Yellow pigment in urine is also formed from thebreakdown of heme by the liver. It is then deposited inthe blood and later removed from the kidneys.Lungs – Expiration removes carbon dioxide but it also resultsin the loss of water.Intestine – Certain salts, such as those of iron and calcium areexcreted directly into the cavity of the intestine by theepithelial cells lining it and become part of feces.Kidneys – Excrete urine, which contains a combination of theend products of metabolism.
6 Position of the kidney in the body: The two kidneys lie in the lower, dorsal part of the abdomen.They receive blood from the renal arteries to be cleaned.The wastes, to be excreted, called urine collects in the pelvicregion of each kidney from where they are conducted byperistalsis down to the urinary bladder.When the urinary bladder becomes full, stretch receptortrigger urination, and the fluid is excreted.
7 Microscopic Anatomy of the Kidney: The kidney is composed of over 1 million nephrons (or renal corpuscles)Bowman’s capsule and proximal convoluted tubule are located in thecortex.Loop of Henle in the medullaDistal convoluted tubule in the cortexCollecting ducts are located in the medulla and cortexRenal Artery – Bring blood to the kidneys to be “cleaned” (high ureacontent)Renal Veins – Returns blood that is cleaned (Low urea content, noglucose)Each nephron has its own blood supply. Including 2 capillary regions:1. At the Glomerulus2. Surrounding the rest of the nephron
10 Function of the Nephron 1. Pressure filtration:Blood enters the Glomerulus which is surrounded by the Bowman’scapsule. Here, occurs. Water, nutrients, andwastes enter the Bowman’s Capsule. Large organic molecules donot enter. The liquid that collects in the Bowman’s capsuleis blood plasma minus blood proteins.Filtered Blood Components:WaterNitrogenous WastesNutrientsSalt (ions)Non-Filtered Blood Components:Formed elements- (blood cells and platelets )ProteinsBlood pressure is very important. If blood pressure is too low,filtration will not occur. A hormone called rennin is released froma specialized tissue in the Glomerulus that causes theconstriction of the Glomerulus thus the blood pressure isincreased to an adequate level.
12 2. Tubular Reabsorption: occurs mainly at the proximal convoluted tubule. Requirednutrients glucose, amino acids, Vitamins, Minerals saltmolecules and some water are reabsorbed into the peritubularcapillary network. Requires ATP.
13 3. Tubular Excretion:Occurs at the distal convoluted tubule. Excess molecules in the blood,such as H+ ions, Histamine, Penicillin, and ammonia are secreted intothe tubule from the blood, thereby helping to maintain homeostasis.Helps maintain blood pH5. Concentrated Urine from the collecting tubule collect and goes tothe Renal pelvis
14 4. Reabsorption of Water: The body can not afford to lose all this water. It must bereabsorbed into the blood. The cells of the loop of Henle activelypump Na+ out of the tubule and K+ into the nephron.The result of this is that the negative ion (Cl-) and water followthe sodium by osmosis (to even out electrical and concentrationgradients)Water is reabsorbed along the entire length of the nephron.There fore urine is concentrated. The blood in the capillaries arehypertonic to the fluids in the fluid spaces. The loop of Henlecreates a high osmotic pressure in the medulla. The fluid going upthe distal side of the loop of Henle has a greater concentration ofwastes and little nutrient value.
15 5. Excretion:Concentrated Urine from the collecting tubule collect and goesto the Renal pelvis
16 Antidiuretic hormone (ADH) - Negative feedback ADH – controls reabsorption of water.ADH increases the permeability of the distal convolutedtubule and collecting duct so that more water can bereabsorbed.Therefore a decreased amount of urine results, but anincrease in urine concentration. Water and Urea=Urine.Urea is a waste product in the metabolism of proteins.With more water being reabsorbed, blood volume tends to beincreased.
17 If too little water is taken in orally, the hypothalamus releases a hormone into the nerve tract to the posterior pituitary gland.The posterior pituitary gland releases ADH and more water isabsorbed by the kidneys to maintain blood volume.PH of blood is maintained by tubular excretion. If pH is too low,Hydrogen ions are secreted into the nephron.Alcohol has a negative effect on ADH. It sends a falsemessage to the hypothalamus that there is too much waterin the blood. ADH is not released in fact it is inhibited.Therefore water is not reabsorbed and is lost in the urine.That is why drinking alcohol, results in a lot of urinationand dehydrated.
18 Aldosterone - Negative feedback Hormones which regulate the level of sodium and potassiumin the blood.If sodium is too low, aldosterone causes more sodium to bereabsorbed. If sodium concentration is high release ofaldosterone is inhibited.Adrenal Cortex controls this hormone. The effect of this is thesame as that of ADH – more water is reabsorbed due toosmosis in the loop of Henle