Digestive & Excretory Systems PDF

Functioning Systems By Prof. Dr. Eman Salah Abdel-Reheim Food Assimilation  Learning Objectives At the end of this lecture, student must be able to know: 1. General Function of Digestive System 2. Mechanical & Chemical Digestion 3.Simplest Form...

Functioning Systems By Prof. Dr. Eman Salah Abdel-Reheim Food Assimilation  Learning Objectives At the end of this lecture, student must be able to know: 1. General Function of Digestive System 2. Mechanical & Chemical Digestion 3.Simplest Forms of Nutrients & their Absorption 4.Simple Outlines about Metabolism Functions of Digestive System Breaks down food into molecules Molecules are absorbed into blood and are carried throughout the body Wastes are eliminated from the body Food Assimilation How does the body get energy from food? Starting firstly by digestion in the digestive system Digestion: Process by which the body breaks down food into small nutrient molecules  Types of Digestion Mechanical Digestion Foods are physically broken down into smaller pieces. Begins when you take your first bite of food Cutting by teeth is the first stage in mechanical digestion Chemical Digestion Chemicals produced by the body break foods into smaller chemical building blocks. Begins in the mouth Food Assimilation  Mechanical Digestion Expressions Mastication = chewing & enzymatic breaks down by saliva. Deglutition= swallowing, voluntary in the mouth & involuntary in the esophagus.  Mechanical Digestion Churning in the stomach forming chyme. Peristalsis = contraction of circular muscle Segmentation = contraction of longtudinal muscle (backward and forward movement) till the colon  Chemical Digestion Digestive Juices Saliva from parotid, sublingual & submandibular Gastric: Chief cells for pepsinogen & parietal for HCl. Pancreatic: by the exocrine cells of the pancreas. Bile is produced by the liver and stored in the gall bladder and secreted in the small intestine to help in lipid digestion. Intestinal Juice is secreted by the mucosa of the small and large intestine. N.B. All the digestive juices contain digestive enzymes Enzyme=Substance+ ase, Enzyme+ gen= inactive enzyme  Chemical Digestion Accomplished by enzymes, In – Mouth (carbohydrates)- salivary amylase – Stomach (proteins)- pepsin – Small intestine (Lipids) Trypsin, chymotryposin, amylase and lipase From the pancreas maltase, sucrase lactase and peptidases from intestinal villi Food Assimilation  Absorption After digestion the simplest forms of food are; glucose, amino acid & fatty acids Absorption is the passage of these simple nutrients through the intestinal mucosa to the blood. Amino acids & glucose are transmitted to the blood by 2nd ry active transport Fatty acids into lymph by simple diffusion  Metabolism Catabolism Hydrolysis monomers. Cellular Respiration oxidation of monomers to yield energy Anabolism – Cell maintenance and repair – Growth – Formation of secretions – Nutrient reserves  Metabolism Substances Catabolic processes Anabolic processes Glucose glycolysis Glycogenesis Kreb’s gluconeogenesis electron transport chain Fatty acids β-oxidation Lipogenesis Kreb’s electron transport chain Amino acids deamination Synthesis of Kreb’s nonessential amino acids electron transport chain  Learning Objectives At the end of this lecture, student must be able to know ✓ Functions of urinary system ✓ Anatomy of urinary system ✓ Nephron structure ✓ Urine formation: Filtration Reabsorption Secretion ✓ Urine Composition ✓ Factors affecting kidney function ✓ Hemodialysis  Function of the Urinary System Why do kidneys produce urine? To regulate blood composition and volume Maintain Homeostasis So, Its Function is; ▪ Disposal of metabolic waste Urea, creatinine, ammonium, uric acid ▪ Maintenance of water-salt and electrolyte balance Sodium, potassium, bicarbonate, etc. ▪ Maintenance of acid-base balance Blood pH must be approx. 7.4 Structure & Anatomy of the Urinary System Human Structure & Anatomy of the Urinary System Kidneys (Latin renes= kidney): Found at the back of the abdomen (one on each side) just below the diaphragm. The left kidney is located at about the T12 to L3 vertebrae, whereas the right is lower due to slight displacement by the liver. Each kidney weighs about 125–175 g in males and 115–155 g in females. They are approximately 11–14 cm in length, 6 cm wide, and 4 cm thick. Both kidneys are supplied with oxygenated blood by the renal arteries and use 20-25% of the oxygen. Structure & Anatomy of the Urinary System Ureters: They are 25 cm long muscular. If urine backs up or is allowed to stand for more time (e.g., in ureter or urinary bladder stones), a kidney infection can develop. Bladder: A triangle-shaped, hollow organ is located in the lower abdomen. The bladder's walls relax and expand to store urine, while it contract and flatten to empty urine through the urethra. The urinary bladder receives urine from each of the kidneys via the ureters. The bladder can hold up to 600 ml of urine. A typical healthy adult bladder can store urine till 9-10 hours. Urethra: It is a tube that carries urine to exit from the body.  Kidney Anatomy Kidney is protected from the outside by fibrous tissue, fat, muscle and ribs. It is consisted of an outer renal cortex and inner medulla then pelvis.  Nephron Nephron is the structural & functional unite of the kidney, it is composed of; – Renal corpuscle: ▪ Glomerular capsule (cup-shaped) ▪ Capillary network (glomerulus) – Renal tubules ▪ Proximal convoluted tubule (PCT): ▪ Nephron loop (Loop of Henle) Each limb contains a thin segment and a thick segment ▪ Distal convoluted tubule (DCT)  Steps in Urine Formation ֍ Filtration: water and small molecules removed from blood, into the renal capsule. It is a pressure filtration, depends mainly on size. ֍ Reabsorption: water and essential molecules returned to blood, in the renal tubules. ֍ Secretion: wastes and excess salts added from body fluids to tubular fluid (urine), in the renal tubules.  Glomerular Filtration Rate ✓ The amount of filtrate produced by the kidneys each minute= Glomerular Filtration Rate (GFR) ✓ 20% of total BL. enter the kidneys every minute, about 1000-1200 ml/min. ✓ 625 ml of plasma only pass as filtrate. Filtrate = plasma - proteins ✓ Only 20% of 625 pass in the tubules. ✓ 125-130 ml of this filtrate only goes through the renal tubules ✓ GFR = 125 ml/min X 60min X 24hr → 180 liters/day ✓ The kidneys can pressure filter 150-200 liters of plasma per day  Forces Affecting on Filtration ▪ Glomerular capillary hydrostatic pressure → due to blood hydrostatic pressure against capillary wall (GHP)= +55mmHg ▪ Blood osmotic (colloidal) pressure due to the presence of solutes (proteins) in the blood (BOP)= -30mmHg ▪ Capsular hydrostatic pressure → Glomerular filtration pressure= 55-(30+15)=10mmHg pressure of filtrate against Bowman’s capsule wall (CHP)= -15 mmHg Net filtration rate = +10mmHg → fluid moves from the glomerulus into the capsule  Reabsorption 180 liters of filtrate is produced/ day, but only about 2 liters of urine is produced/day, So ≈ 99% is reabsorbed Reabsorption of nutrients, electrolytes, water by many transport mechanism through the renal tubules; - Proximal Convoluted Tubule (PCT) - Loop of Henle - Distal Convoluted Tubule (DCT)  PCT-Reabsorption “Obligatory Reabsorption” ▪ Glucose, amino-acid, will be pumped out of the tubules by 2ndry active transport (actively by carrier ) ▪ The transporter for glucose on the basolateral membrane has a limited capacity to carry glucose back into the blood. ▪ If blood glucose rises above 180 mg/dl, some of the glucose fails to be reabsorbed and remains in the urine → glucosuria (physiologically or in diabetes mellitus)  PCT-Reabsorption ▪ 70% of sodium and water are reabsorbed in PCT ▪ Water will move into the peritubular space by osmosis (passively) ▪ Chloride will follow sodium by simple diffusion into the peritubular space. Accumulation of positive charges draws chloride out. ▪ Some compounds present in high concentration in the filtrate but low in the blood, can move through Types of transport in reabsorption diffusion. ▪About 30 mL/min of isotonic filtrate is delivered to the loop of Henle, where urine is concentrated. (Remember that I started by ≈ 125ml filtrate/ml)  Loop of Henle- Reabsorption Characteristics of Loop of Henle: - Descending loop: permeable to water, it moves out of the tubules down its osmotic gradient. It has no sodium pumps It dips down into the hypertonic environment of the kidney medulla - Ascending loop: thick epithelium, impermeable to water but has many sodium pumps. The filtrate rich its highest concentration at the tip of Henle loop and its lowest concentration at the distal convoluted tubule  So, why is the loop of Henle useful? ✓ The longer the loop, the deeper it travel into the hyperosmotic medulla so, more reabsorption & more concentrated tubular fluid is formed. ✓ The collecting tubule runs through the hyperosmotic medulla → more ability to Desert animals reabsorb H2O have long nephron Loop → More H2O is reabsorbed  DCT and CT-Reabsorption “Facultative-Reabsorption” ▪ Reabsorption here depends on body's need. ▪ DCT and CT tubular walls are different from the PCT and Loop of Henle wall. ▪ DCT & CT walls have tight junctions, and the membrane is impermeable to water ▪ The cell membrane has receptors able to bind and respond to various hormones: ADH (anti-diuretic hormone, reabsorb H2O) and Aldosterone (reabsorb Na+) ▪ The binding of hormones will modify the membrane permeability to water and ions to be reabsorbed according to the body's need.  Regulation of ADH secretion ✓ADH increases water retention, thus reducing urine volume, and prevents dehydration. ✓It regulates decreased blood volume & decreased BP by baroreceptors (specialized neurons found in cardiovascular system sense changes in blood pressure). ✓It also, regulates increased salt concentration by stimulating the osmoreceptors (specialized neurons in the hypothalamus to monitor changes in extracellular osmolality). What are the symptoms of ADH-lack? Diabetes insipidus disease  DCT and CT-Reabsorption (Urine Concentration) ADH is low → no binding to its ADH is released by post. Pituitary, receptors → H2O is not reabsorbed binds to receptors in CT, back into the blood. H2O remains aquaporin channels open → H2O in the renal tubule → high urine moves into the blood → low urine volume & low urine concentration volume with high concentration  Secretion and Excretion ❑ Secretion: Selective transport of molecules from blood in the peritubular capillaries to the lumen of the renal tubules. ❑ Example of excreted waste products: urea, excess drug metabolites, K+, H+, Ca++. ❑ Excretion: the body must get ride of urine; molecules are dumped outside the tubules. Urine formation summary  Urine Composition ✓ Urine composition varies from time to time and reflects the amounts of water and solutes that the kidneys eliminate to maintain homeostasis. ✓ Urine is 95-96% water, and also contains urea, uric acid, a trace of amino acids, and electrolytes. ✓Daily production=600ml-2500ml/day (500ml < oligourea, 2.5L> polyurea) Factors that affect kidney function ❑ ADH: prevents excess water loss from kidneys= less urine volume & concentrated ❑ Alcohol: inhibits secretion of ADH = more urine volume & diluted ❑ Aldosterone: prevents excess loss of sodium and water from kidneys = less urine volume, not affect on urine concentration (Why?) ❑ Caffeine: increases rate of salt and water loss from kidneys, as it blocks adenosine receptors. ❑ Increased blood pressure: increase rate of water loss from kidneys.  Notes ⅌ Kidney diseases affect structure and function at nearly 5 stages, from nearly normal function to failure. ⅌ Kidney failure is fatal if untreated. ⅌ This is treated by Dialysis or Transplantation ⅌ Kidney is the first successful organ transplanted in humans in 1954  Hemodialysis ֎ Dialysis is a treatment for people who have kidney failure. ֎ The kidneys don’t filter blood, as a result, wastes and toxins are built up in the blood. ֎ Dialysis does the work of the kidneys, removing waste products from the blood. ֎ Inside the dialyzer, there are two sides separated by thin membrane, one side is for blood and the other for the dialysis solution (dialysate). ֎ Passive diffusion occurs from the high to the low concentration gradient between the patient’s blood and dialysate used. ֎ Waste products are removed into the dialysate solution while essential minerals & amino acids are moved from the dialysate to the blood. Meet you in the 1st Exam 40