Unit 8: The Urinary System Flashcards
What are the excretory organs of the body?
Skin (Integumentary System)
Lungs (Respiratory System)
Kidneys (Urinary System)
How is skin an excretory organ?
Excretes excess salt and some water through sweat
How are the lungs an excretory organ?
Excrete carbon dioxide and some water through expiration
How are the kidneys an excretory organ?
Excrete most metabolic wastes
What are the functions of the urinary system?
Elimination of metabolic wastes
Regulation of ion levels (e.g. Na, K, Ca)
Regulation of acid-base balance (i.e. blood pH) - It alters the levels of H and HCO3 in the blood
Regulation of blood pressure - kidneys are the MOST important regulator of blood pressure
Elimination of biologically active molecules - hormones and drugs
Production and release of hormones
Potential to engage in gluconeogenesis
How does the urinary system produce and release hormones?
Calcitriol is an active form of vitamin D and Erythropoietin (EPO) is stimulated in response to low blood oxygen levels to stimulate red bone marrow to increase erythrocyte production.
How does the urinary system have the potential to engage in gluconeogenesis?
It is engaged during prolonged fasting or starvation and produces glucose from noncarbohydrate sources to maintain glucose levels.
What do the kidneys do?
They filter blood and remove waste products and convert filtrate into urine.
What is the function of the ureters?
To transport urine from kidneys to urinary bladder
What is the bladder?
It is an expandable muscular sac of smooth muscle that can store as much as 1 L of urine.
What is the function of the Urethra?
Eliminates urine from the body
What is the position of the kidneys?
They are located on the posterior abdominal wall lateral to the vertebral column. The left kidney is between T12 and L3 of the vertebrae. The right kidney is about 2 cm inferior to te the left to accommodate the liver but both are only partially protected by the rib cage. Which makes them vulnerable to forceful blows to the inferior region of the back. The kidneys are positioned posterior to the parietal peritoneum (retroperitoneal) and it is the only anterior surface covered with parietal peritoneum.
Explain the gross anatomy of the kidneys.
The kidneys are two symmetrical, bean-shaped organs that are about the size of your hand to your second knuckle. They have a concave medial border know as the hilum where vessels, nerves, ureter connect to the kidney. Their lateral border is convex and the adrenal gland rests on the superior aspect of the kidney.
What tissue layers is the kidney supported by?
Fibrous capsule
Perinephric fat
Renal fascia
Paranephric fat
What is the fibrous capsule?
It is made of fibrous connective tissue that is directly adhered to the external surface of the kidney. It is used to maintain the kidney’s shape, protects it from trauma and prevents any pathogen penetration.
What is the Perinephric Fat?
It is composed of adipose connective tissue that is external to the fibrous capsule and it cushions and supports the kidney.
What is the renal fascia?
It is external to the perinephric fat and anchors the kidney to surrounding structures.
What is the paranephric fat?
It is the outermost layer that surrounds the kidney and is composed of adipose connective tissue. It cushions and supports the kidney to help hold it in place.
Briefly explain how the kidneys work?
They are used to filter out ALL small substances from the blood and return most substances back to the blood. They excrete the excess substances back out of the blood into the urine. Some of these things include toxic substances the body doesn’t want like urea and nitrogenous wastes. Also excess of useful substance in the body like hormones and water-soluble vitamins.
How can urine be characterized?
Urine is the product of filtered and processed blood plasma it is sterile unless it is contaminated with microbes in the kidney or urinary tract. It can be characterized by composition, volume, pH, specific gravity, color and smell.
How can urine be characterized by its composition?
It is made up of 95% water and 5% solutes like salts, nitrogenous wastes, some hormones, drugs, and small amounts of ketone bodies. Some abnormal constituents include glucose, protein, bile and blood cells.
How can urine be characterized by its volume?
On average we produce 1 to 2 L per day. It can vary depending on fluid intake, blood pressure, temperature, diuretics, diabetes, and other fluid secretions (e.g. sweating expiration, faeces). A minimum of 0.5 L is to eliminate wastes from the body, anything below 0.40 will begin to accumulate in the blood and you will need a dialysis.
How can urine by characterized by its pH?
Normally urines pH is between 4.5 to 8.0. The more acidic the larger the amounts of protein or wheat in your diet and the less acidic is with a diet a high fruits and vegetables. In can be influenced by metabolism and infection.
How can urine be characterized by specific gravity?
The density of a substance compared to the density of water. Specific gravity is slightly higher than water due to solutes.
How can urine be characterized by color?
Color ranges from almost clear to dark yellow, it depends on concentration of urobilin. With an increased volume of urine, the lighter the color.
How can urine be characterized by smell?
Urinoid is the term for the normal fresh smell of urine. It may develop ammonia smell if allowed to stand and typically it has a fruity smell from diabetes.
What does the urinary tract consist of?
Ureters, Urinary Bladder, and the urethra
Explain the function and structure of the ureters.
It is long epithelial-lined fibromuscular tubes of smooth muscle that conduct urine from the kidneys to the urinary bladder. It originates from the renal pelvis as it exits the hilum of the kidney and enters the posterolateral wall of the base of the urinary bladder. It is distensible and impermeable to urine and it contract rhythmically with the presence of urine in order to propel urine towards the bladder. Ureteric jets are used to empty into the bladder.
Explain the structure and function of the urinary bladder.
It is an expandable, muscular (smooth muscle) reservoir for urine and is positioner immediately posterior to the the pubic symphysis. In females it is anteroinferior to the uterus but for males in is anterior to the rectum and superior to the prostate gland in males. It has a retroperitoneal which is the superior surface covered with parietal peritoneum.
Explain the structure and function of the trigone.
The trigone is the posteroinferior triangular area of the bladder wall and is formed by imaginary lines connecting the ureter openings and the urethra. It remains immobile as the bladder fills up and empties. It acts as a funnel to direct urine into the urethra during contraction. Infections are very common in this area.
Explain the structure and the function of the urethra.
The urethra is an epithelial-lined fibromuscular tube that exits urinary bladder through a urethral opening. It conducts urine to the exterior of the body and it has two sphincters to restrict the release of urine until bladder pressure is high enough. There is the internal and external urethral sphincter.
Explain the structure and function of the internal urethral sphincter.
It is involuntary, superior sphincter composed of smooth muscle. It surrounds the neck of the bladder and is controlled by the autonomic nervous system.
Explain the structure and function of the external urethral sphincter.
It is inferior to the internal urethral sphincter and is formed by skeletal muscle fibres of the pelvic diaphragm. It is voluntary sphincter controlled by the somatic nervous system and you are learned to control this muscle during “toilet training”.
Explain the structure and function of the female urethra.
The single function is to transport urine from the urinary bladder to the exterior and is approximately 4 cm (1.6 in) in length.
Explain the structure and function of the male urethra.
It is a passageway for urine and semen. It has three segments: prostatic urethra, membranous urethra, and spongy urethra. It is approximately 19 cm (7.5 in) in length.
What is micturition?
It is the expulsion of urine from the bladder, associated with two reflexes: storage reflex and micturition reflex
Explain the storage reflex.
This is continuous sympathetic stimulation that causes relaxation of detrusor to accommodate urine. Contraction is then stimulated to the internal urethral sphincter so that urine is retained in the bladder. The external urethral sphincter is continuously stimulated by pudendal nerve to remain contracted.
Explain the micturition reflex.
The volume of urine in the bladder is between 200 to 300 mL and the bladder is distended and baroreceptors are activated in the bladder wall. Visceral sensory neurons signaled by baroreceptors to stimulate micturition center in the pons. The micturition center alters the nerve signals down the spinal cord through the pelvic splanchnic nerves. The parasympathetic stimulation causes detrusor muscles to contract and causes internal urethral sphincter to relax.
Explain the conscious control of urination through micturition.
It is first initiated from the cerebral cortex through pudendal nerve which causes relaxation of the external urethral sphincter facilitated by voluntary contraction of abdominal and expiratory muscles. After emptying, the detrucor muscle relaxes and neurons of the micturition reflex are inactivated while neurons of the storage reflex are activated. If urination is not activated at the time of the first reflex then the detrusor muscle will relax due to stess-relaxation response. The micturition reflex will be activated again after another 200 to 300 mL are added and urination will occur involuntarily between 500 to 600 mL. The bladder can be emptied prior to the micturition reflex from abdominal muscles contracting to compress the bladder. This initiates the micturition reflex by stimulating stretch receptors.
What are the renal columns?
The extension of the cortex projecting into the medulla.
What are the renal pyramids?
Portion of medulla divided by renal columns. The point of the medullary pyramids is called the renal papilla.
What is the corticomedullary junction?
the meeting point of cortex and medulla
What is the renal lobe?
renal pyramid and portions of adjacent renal columns, renal cortex is external to the base
What is the renal sinus?
It is medially located in the urine drainage area and is organized into minor calyces, major calyces, and renal pelvis.
What is the minor calyx?
It is a funnel shaped structure at the end of the renal pyramids and collecting ducts drain into them.
What is the major calyx?
It is formed from merged minor calyces.
What is the renal pelvis?
it is formed from merged major calyces.
What is a nephron?
It is a microscopic functional unit of the kidney and consists of the renal corpuscle and renal tubule. All of the corpuscle and most of the tubules reside in the cortex.
What is the renal corpuscle?
It is the enlarged bulbous region of the nephron within the renal cortex. It is composed of two structures: glomerulus and glomerular capsule (aka Bowman’s capsule)
What is the glomerulus?
It is a tangle of capillary loops, termed glomerular capillaries. Blood enters through the afferent arteriole and exits through the efferent arteriole.
What is the glomerular capsule (aka Bowman’s capsule)?
It has an internal permeable visceral layer and an external impermeable parietal layer. There is a capsular space between the two layers that receives filtrate and leads to tubule.
What is a renal tubule?
The renal tubule consists of three continuous section: Proximal convoluted tubule (PCT), nephron loop (aka Loop of Henle), and the distal convoluted tubule (DCT).
