Male Urinary System: Structure & Function

This presentation provides a detailed explanation of the **urinary system in a man**, focusing on both theoretical aspects and visual representations. The urinary system plays a crucial role in filtering waste products from the blood and eliminating them through urine. It is composed of several key organs, including the **kidneys**, **ureters**, **bladder**, and **urethra**. Each part has a specific function, which will be elaborated with corresponding diagrams and images to ensure a clear understanding of the system.

Firstly, the **kidneys**, two bean-shaped organs located on either side of the spine, are responsible for filtering the blood. They remove waste products, excess salts, and water, forming urine. This filtration process is vital for maintaining the body’s balance of fluids, electrolytes, and pH. The presentation will include detailed images showing the internal structure of the kidney, including the **nephrons**, the tiny filtering units that regulate the composition of blood.

Once urine is formed, it is transported to the bladder through the **ureters**, two thin tubes that connect the kidneys to the bladder. The ureters move urine through peristaltic movements, ensuring that it flows steadily downwards. The visual aids will highlight the anatomical placement of the ureters, helping to visualize the pathway of urine.

The **bladder** is a hollow, muscular organ located in the lower abdomen that temporarily stores urine. When it fills, nerve signals trigger the urge to urinate. The bladder’s ability to expand and contract will be demonstrated with diagrams, illustrating how the bladder accommodates urine and then expels it.

Lastly, urine exits the body through the **urethra**, a tube that leads from the bladder to the external opening. In men, the urethra is longer and passes through the **prostate gland** before reaching the penis. The images will show this extended pathway and its relation to surrounding organs, emphasizing the differences between male and female urinary systems.

Overall, this presentation combines theoretical explanations with carefully curated images, enabling a comprehensive understanding of the male urinary system, its components, and their functions.

1. Urinary system in man The urinary system of human is consists of A pair of kidney A pair of ureters A urinary bladder A urethra Kidneys are reddish-brown bean shaped organs, situated at the dorsal side of the abdominal cavity on either side of the vertebral column. The kidneys help remove waste products from the body, maintain balanced electrolyte levels, and regulate blood pressure. The right kidney is generally slightly lower than the left kidney to make space for the liver.

2. Each kidney is approximately 3 centimeters (cm) thick, 6 cm wide, and 12 cm long. In males, the average weight of the kidneys is roughly 129 grams (g) for the right one and 137 (g) for the left. A tough, fibrous renal capsule surrounds each kidney and provides support for the soft tissue inside. The adrenal glands lie on top of the kidney. Each kidney has an area in the center of concave surface which faces the vertebral column; this area is called hilus.

3. The renal artery, renal vein, nerve and ureter are connected to each kidney at the hilus. The ureter is a narrow tube which connects the kidney to the urinary bladder. Urine passes through ureter to the urinary bladder. Kidney are the main organs in the human excretory system, which takes part in the filtration of the blood before the urine is formed. The kidney is made up of millions of smaller units called nephrons which are also functional units.

4. On the inside, the kidney is divided into an outer renal cortex and an inner renal medulla. The outer layer of the kidney is a tough capsule. The urinary bladder is a thin walled muscular bag situated towards the bottom of abdominal cavity in front of the rectum which stores urine. The urethra is a tube which comes out from the urinary bladder, runs down and opens outside the body through urinary opening. Kidney is enclosed in a membrane called peritoneum.

5. A fluid is filled in between peritoneum and kidney called peritoneal fluid which reduces the friction. The kidney has three main parts: the cortex, the medulla, and the pelvis. Cortex is the outer dark brown portion, and cortex is covered & protected by a fibrous capsule. The medulla is the inner lighter portion of the kidney, & it contains the conical projection called renal pyramids; the human kidneys contain 12-16 pyramids. The medulla contains nephrons, nephrons are the basic functional units of the kidney.

6. Nephrons are tiny kidney tubules where osmoregulation occurs to produce urine. The kidneys are connected to the ureter at pelvis, pelvis is a funnel like space, it is the enlarged portion of ureter inside the kidney. A nephron is a microscopic structural & functional unit of kidney. Nephron is made of a renal corpuscle & a renal tubule, number of nephrons open into a tube called collecting duct. The renal corpuscle consists of a network of capillaries called glomerulus & bowman’s capsule. The corpuscle & tubule both are connected, they are made of epithelial cells.

7. The tubule has five parts, namely: proximal convoluted tubule which is connected to the bowman’s capsule. Which passes into the medulla. loop of henle which has 2 parts, ascending loop of henle & descending loop of henle. The tubule enter into medulla, extends into a renal pyramids & makes a U like tube, back into the cortex. Distal convoluted tubule when the tubule enters the cortex again, it becomes convoluted again. Bowman’s capsule each nephron begins in the cortex as a cup like structure. Filtration of blood takes place in the bowman’s capsule. Blood reaches the glomerulus through afferent arterioles of the renal artery.

8. The amount of blood that enters the bowman’s capsule while passing through glomerulus is called filtrate, the filtrate contains glucose, amino acid, salts, and water. This filtrate passes through renal tubule where selective reabsorption takes place. The useful substances like glucose, amino acid, water etc are reabsorbed. The remaining filtrate is called urine which is collected in the collecting duct. Bowman’s capsule with glomerulus are collectively called malpighian body or renal corpuscle.

9. Blood capillaries surround a loop of henle’s unite to form venule, which ultimately joins to form a branch of renal vein. The urea is formed within the liver cells. The liver stores surplus glucose of food by converting it into glycogen & other food substances but it cannot store the proteins. The excessive amino acid break & get some energy from it. The amino group (NH2) is removed from amino acid called deamination. This NH2 group is converted into ammonia (NH2) which is very poisonous, it may kill the cell when stored in high concentration.

10. The liver cells quickly convert NH3 into less toxic substance urea. This urea is carried by blood to kidneys & excrete out in the form of urine. A small amount of urea is also excreted in sweat as well. Urine formation: waste is excreted from the human body, mainly in the form of urine. Constituents of normal human urine include 95 percent water & 5 % solid wastes, it is produced in the nephron, which is the structural & functional unit of the kidney. Urine formation in our body is mainly carried out two main process; (i) filtration (ii) reabsorption

11. (i) Filtration: filtration is the process of taking out material from blood. It is of two types: (a) ultrafiltration (b) selective filtration (a) Ultrafiltration: In the first stage non-selective, ultra-filtration (filtration at molecular level) of blood occurs while passing through the glomerulus of the malpighian body. Two factors are responsible for this ultrafiltration. Both the capillary walls of glomerulus & the walls of bowman’s capsule are sieve-like in nature, which permit all the molecules except plasma proteins & blood cells to pass through them. (b) Selective filtration: selective filtration occurs at proximal & distal convoluted tubules when blood flows into peritubular capillaries, the remaining amount of urea filter out from blood by active transport. It requires some energy.

12. Reabsorption: Active reabsorption of the glomerular filtrate occurs in the proximal convoluted tubule, so a large amount of filtrate is reabsorbed & returned to circulation. Here glucose amino acids, water, salts are reabsorbed. The filtrate being almost urine now is passed into the collecting duct where the concentration of water in the filtrate is finally adjusted. (a) non-selective reabsorption (b) selective reabsorption

13. Non-selective reabsorption: Non-selective reabsorption occurs at distal & proximal convoluted tubules without any selection. Selective reabsorption: loop of henle & collecting duct selectively reabsorb substances with the assistance of hormones like antidiuretic hormone (ADH), parathyroid hormone, & calcitonin.

14. Role of kidneys in osmoregulation: The water potential (capacity to loose water) of blood in the body has to be kept constant because big & sudden change in the water potential of blood can lead to serious problems e.g. if plasma becomes very much dilute water will enter the blood cells will swell & possibly burst. On the other hand if the blood plasma becomes too concentrated, water will move out of the cell by osmosis, as a result of it the blood cells, tissues will become dehydrated & shrink.

15. This control of water & salt content of the body is known as osmoregulation. Kidney is not only an excretory organ, it also regulates water & salt balance in the blood. Kidneys makes sure that the concentration of blood stays more or less constant. Sweating i.e loss of H2O. Water potential of blood decreases.

16. ADH hormone release from pituitary gland. Collecting duct of nephron absorb H2O into cell-capillaries. Urine produce in small quantity. Concentrated urine produce. Water potential of blood returns to normal. Dilute urine produce.

17. Renin produce in high quantity. Collecting duct of nephron absorb less H2O into cell-capillaries. Pituitary gland releases less ADH. Water potential of blood increase. Intake of H2O by drinking.