The Urinary System: Anatomy, Functions, and Diseases

The Urinary System PSW 1022 Introduction The urinary system acts as a purification plant, cleaning the blood of waste materials. The liver does some purification, but the urinary system controls electrolyte and fluid balances for your body. **Remember ho...

The Urinary System PSW 1022 Introduction The urinary system acts as a purification plant, cleaning the blood of waste materials. The liver does some purification, but the urinary system controls electrolyte and fluid balances for your body. **Remember homeostasis**  System Overview The urinary system consists of: 2 kidneys; bean-shaped organs located in the superior dorsal abdominal cavity that filter blood and make urine. Ureter (2): a tube that carries urine from each kidney to the urinary bladder Urinary bladder: is basically an expandable sac that holds urine The urethra: is the tube that transports urine from the bladder to the outside of the body. ** Remember 2 ureters, 1 urethra Figure 17-1 Anatomy of the urinary system. Main Functions The kidneys have three main jobs: 1. filter blood 2. reabsorb and secrete ions 3. produce urine Without this important function you would die in a few days. External Anatomy of the Kidney The kidney is covered by a fibrous layer of connective tissue called the renal capsule. The indentation that gives the kidney it’s bean shape is called the renal hilum.  At the hilum: Renal arteries bring blood to the kidneys to be filtered renal veins take the filtered blood away from the kidney to go back to the heart The ureter is also attached at the hilum to transport urine from the kidney to the bladder YouTube Video: Filtration, Reabsorption, Secretion (production of urine) System Overview To make urine, 3 processes are necessary: Filtration – filtering the blood. What passes through the filter is called a filtrate. Reabsorption – substances stay in the body after being removed from urine Secretion – substances move from the blood stream and are eliminated from the body in the urine These three processes take place in the millions of nephrons, which are the functional units of the kidney. The Nephron The nephrons consist of millions of microscopic funnels and tubules. The nephron can be divided into two distinct parts: The renal corpuscle – a filter The renal tubule – where reabsorption and secretion take place  Figure 17-4 The nephron. YouTube Video: Filtration, Reabsorption, Secretion (production of urine)  Internal Anatomy of Kidney Blood vessels Each afferent arteriole leads to a ball of capillaries called a glomerulus Efferent arterioles leave from the glomerulus Refer to explanation in notes section Renal Tubule Follow these steps along with the picture: 1. Glomerular filtrate (definition in note section) travels from the glomerular capsule into the first part of the renal tubule, the proximal tubule. 2. From the proximal tubule, glomerular filtrate flows into the nephron loop (or the Loop of Henle). 3. The nephron loop consists of the descending loop and the ascending loop. Figure 17-4 The nephron. Renal Tubule Follow these steps along with the picture: 4. Glomerular filtrate travels from the nephron loop to the distal tubule. 5. From the distal tubule, glomerular filtrate flows into one of several collecting ducts. 6. The collecting ducts lead to minor calyces, then to major calyces, the renal pelvis, and the ureter. 7. At this point, the glomerular filtrate is urine. Figure 17-4 The nephron. Figure 17-6 The processes involved in urine formation. Filtration Fluid and molecules pass from the glomerular capillaries into the glomerular capsule. Filtration moves fluid and chemicals into the nephron from blood. The filtrate flows into the renal tubule where the chemistry is controlled by reabsorption and secretion Control of Filtration Filtration is controlled by several factors. 1. Filter size determines what gets through the filter The filter is the capillary wall 2. Substances are moved though a filter by differences in pressure. Pressure pushes substances though the holes in the filter. Remember: Plasma and many of the substances dissolved in plasma, pass through the filter, but blood cells, platelets, and large molecules (like protein), can’t get into a healthy kidney, but stay in the blood vessel. Control of Filtration 3. Changes in blood pressure change filtration rate. As blood pressure increases, the afferent arterioles that lead to the glomerulus constrict, therefore decreasing the amount of blood that gets into the glomerulus. **Since the kidney regulates fluid volume, the kidney can work with the cardiovascular system to regulate blood pressure. Think about it… When the sympathetic nervous system (Fight or Flight) takes over and adrenaline (epinephrine) is released, urine formation slows down. Can you think of why? Reabsorption and Secretion Substances that are reabsorbed pass from the renal tubule into the peritubular capillaries and return to the blood stream. Substances that are secreted pass through the peritubular capillaries into the renal tubule (collecting duct) and eventually leave the body as urine. Some substances, like glucose, are completely reabsorbed while substances like metabolic waste products (urea and creatinine) are almost completely secreted as urine. Urine Formation The kidney controls fluid and electrolyte balance by controlling urine volume and composition. Reabsorption and secretion of substances AREA OF THE WHAT IS WHAT IS SECRETED TUBULE REABSORBED Proximal tubule Water, glucose, Hydrogen ions (H+) sodium, amino acids Descending loop water Urea Ascending loop Sodium chloride Potassium (K+), urea (NaCl) Distal tubule Sodium, water, Potassium, Urea Collecting duct Water, sodium Potassium, Urea chloride (NaCl) Figure 17-9 Sites of tubular reabsorption and secretion. Homeostasis continued… Hormones that are released from the endocrine glands assist the kidneys in maintaining the optimal internal balance. Some will increase the filtration rate and others will decrease the filtration rate and production of urine. All this maintains homeostasis. Urinary Bladder The urinary bladder is a small hollow organ The ability to stretch is enhanced by a series of pleats called rugae. Figure 17-10 The urinary bladder. Urination Reflex As urine accumulates, the bladder fills and stretches. ◦ This stretch triggers the urinary reflex and the need to void to empty the bladder. ◦ When the bladder is full, signals are sent from the bladder to the spinal cord to the brain. ◦ The brain sends signals down the spinal cord, causing contraction of the muscular walls of the bladder, and the bladder empties. Urination Urine leaves the bladder via the urethra, a thin muscular tube lined with several different types of epithelium along its length. Urinary Tract Infections (UTIs) Urinary tract infection is caused by the movement of fecal bacteria into the urinary tract. Symptoms may include: frequent, painful urination bloody or cloudy urine with an unusual odor low abdominal/pelvic pain caused by bladder spasm. Urinary Tract Infections (UTIs) Treatment should begin promptly to avoid kidney damage from infection traveling from the bladder to the kidney. UTIs are more common in women …..WHY? Urinary Tract Infections (UTIs) UTIs are more common in women …..WHY? 1. Urethra is in close proximity to anus (exposure to anal bacteria) 2. Urethra is short (closer to bladder than for males) How can UTIs be prevented? Urinary Tract Infections (UTIs) 1. Prevention: Drinking plenty of water (Why?) Voiding often so urine doesn’t stay stagnant in bladder Making sure to wipe perineum from front to back (Why?) Once diagnosed, UTIs are treated with antibiotics and increased fluid intake. Changes Related to Aging There is a loss of muscle tone in the bladder which can lead to Urinary incontinence Kidney function begins to decline at age 40 and declines at a rate of about 1% per year beyond age 40. How do these impact elderly clients? Changes Related to Aging Loss of muscle tone in the bladder which can lead to urinary incontinence - embarrassing for client, odour, uncomfortable, cold -risk of falls if hurrying to washroom -intentional decreased intake of fluids -skin irritation and breakdown -risk of UTIs with incontinence/wet briefs Changes Related to Aging Kidney function begins to decline at age 40 and declines at a rate of about 1% per year beyond age 40. How does this impact elderly clients? Changes Related to Aging Kidney function begins to decline at age 40 and declines at a rate of about 1% per year beyond age 40. -Elderly clients can produce lower levels of hormones in the kidney that trigger thirst….leading to dehydration….low urine production ….stagnant urine in bladder…increased risk for infection -Kidney function can decline with age which slows excretion of medications from the body. Medications can build up in the body and become toxic References Wilk, M.J., Sorrentino, S. & Remmert, L.N.. (2022). Sorrentino's Canadian textbook for the Support Worker (5th Cdn ed.). Elsevier: Toronto Chapter 29 (page 648) Chapter 32 (page 745-747)