126 Questions
What is the primary role of the liver in waste processing?
To convert waste products into forms that can be excreted
What is the primary function of the kidneys in waste removal?
To maintain the constant concentration of body fluids
What type of waste is excreted by the lungs?
Carbon dioxide
What is the purpose of sweat glands in waste removal?
To regulate body temperature through sweat
What are the by-products of metabolism excreted in sweat?
Salts, urea, and lactic acid
What is the source of urea production in the body?
Liver
What is the approximate weight of the skin in a male adult?
4.5 kg
What is the primary function of proteins in the body?
Building structural materials of cells
Where is the liver located in the body?
Upper abdominal cavity
What happens to excess protein in the body?
It is broken down and removed from the body
What are the end products of protein breakdown in the body?
Amino acids only
What are the primary constituents of cell structures?
Proteins and enzymes
What is the result of deamination?
Formation of ammonia
What is the primary function of the liver regarding ammonia?
To convert ammonia to urea
What is the main function of the skin regarding waste removal?
Excretion of small amounts of urea
What is the effect of ammonia on cells?
It is highly toxic to cells
What is the role of the liver in processing chemicals?
To convert toxic substances into safer forms
What is the fate of bile pigments in the body?
They are passed out of the body with faeces
What is the function of the renal artery in the urinary system?
To carry blood to the kidney
What is the approximate length of each kidney in the human body?
11 cm
What is the name of the microscopic functional unit of the kidney?
Nephron
What is the role of the liver in patients with liver disease?
To process substances for excretion
What is the name of the structure that funnels urine into the ureter?
Renal pelvis
What is the name of the tube that carries urine from the bladder to the exterior?
Urethra
What is the section of the renal tubule that is winding and convoluted?
Proximal convoluted tubule
What is the name of the bend in the renal tubule that resembles a hairpin?
Loop of Henle
What is the structure that multiple distal convoluted tubules merge into?
Collecting duct
What is the length of the renal tubule?
5 cm
What is the name of the chamber in the kidney that channels fluid from the collecting ducts into the ureter?
Renal pelvis
What is the outer layer of the kidney that surrounds the renal cortex and medulla?
Renal capsule
What is the location of the renal columns in the kidney?
Between the renal pyramids
What is the function of the nephron?
To filter waste from the blood
What is the structure that surrounds the glomerulus?
Glomerular capsule
What is the approximate number of nephrons in each human kidney?
1.2 million
What is the name of the knot of arterial capillaries found in the nephron?
Glomerulus
What percentage of blood from the heart is received by the kidneys?
About a quarter
What is the function of the efferent arteriole?
To drain blood away from the glomerulus
What is the purpose of the peritubular capillaries?
To reabsorb essential nutrients from the filtrate
What is the name of the structure that surrounds the glomerulus?
Glomerular capsule
Where does blood enter the kidney through?
Renal arteries
What is the approximate volume of blood that passes through the two kidneys every minute?
1.2 L
What is the main reason for the high pressure in the glomerulus?
The narrowing of the efferent arteriole
What is the term for the fluid collected by the glomerular capsule?
Filtrate
What is the main component of blood that is not present in the filtrate?
All of the above
What is the function of the glomerular capsule?
To collect the filtrate
What is the purpose of the high pressure in the glomerulus?
To force water and dissolved blood components out of the capillaries
What is the function of the capillaries in the glomerulus?
To separate the blood from the glomerular capsule
What percentage of plasma is filtered through the capillary walls into the glomerular capsule?
20%
What is the primary composition of the filtrate in the glomerular capsule?
Water, salts, amino acids, and glucose
What is the approximate number of nephrons in each kidney?
1.2 million
Why can't all the plasma be filtered through the glomerulus?
The blood in the capillaries is continually being pushed on by the blood behind it
What is the total amount of filtrate produced by all the renal corpuscles of both kidneys?
High
What percentage of the filtered substance leaves the body as urine?
1%
What is the purpose of the large surface area of the renal tubule?
To facilitate the reabsorption of useful substances
Which substances are partially reabsorbed from the filtrate?
Urea and amino acids
What regulates the reabsorption of water from the filtrate?
Hormonal control
What is the purpose of the convolutions in the renal tubule?
To increase the surface area for reabsorption
What is the term for the regulated reabsorption of water from the filtrate?
Facultative reabsorption
What is the primary function of tubular secretion in the formation of urine?
To remove excess hydrogen and ammonium ions from the blood
What is the effect of the kidneys on the pH of the urine?
They make the urine slightly acidic
What is the route by which urine leaves the kidney?
Collecting ducts → renal pelvis → ureters
What is the name of the muscular organ that stores urine?
Urinary bladder
What is the function of the kidneys in maintaining blood pH?
To remove excess hydrogen ions from the blood
What is the result of tubular secretion on the composition of the blood?
It decreases the concentration of hydrogen ions
What is the primary reason for the high blood pressure in the glomerulus?
To maintain the concentration gradient in the nephron
What is the primary function of the distal convoluted tubule in the nephron?
Active reabsorption of sodium ions
What is the main function of each tubule having two sets of convolutions and a long loop?
To increase the surface area for reabsorption and secretion
What is the primary function of the collecting duct in the nephron?
Active reabsorption of water, depending on the body's water needs
Why is the efferent arteriole smaller in diameter than the afferent arteriole?
To increase the blood pressure in the glomerulus
What is the primary function of the nephron in terms of maintaining blood pH?
Regulation of hydrogen ion levels
What is the approximate volume of water lost daily to remove wastes, regardless of the amount of water available in the body?
Half a litre
What percentage of the filtered substance is reabsorbed during a 24-hour period?
99.9%
What is the approximate amount of water reabsorbed during a 24-hour period?
1485 ml
What is the approximate amount of urea excreted in the urine during a 24-hour period?
8.5 g
What is the approximate amount of glucose reabsorbed during a 24-hour period?
53 g
What is the approximate amount of sodium, chloride, and other ions reabsorbed during a 24-hour period?
1500 g
What percentage of urine is composed of water?
96.0%
What is the main component of urine apart from water?
Urea
What is the percentage of urea in urine?
2.0%
What is the percentage of various ions in urine?
1.5%
What is the percentage of other substances in urine?
0.5%
What is the source of creatinine in muscle?
Breakdown of creatine phosphate
What is the relationship between creatine phosphate and energy?
Creatine phosphate is an energy-rich molecule
What is the nutritional source of purines?
Found in many foods, both animal and plant-based
What is the consequence of creatine phosphate breakdown in muscle?
Production of creatinine
What is the significance of purines in the body?
Purines are a waste product that must be excreted
What is the primary composition of urine, excluding water?
Urea, ions, uric acid, and creatinine
What is normally not present in urine?
Protein and glucose
What percentage of water that enters the nephron is normally reabsorbed?
99%
Which of the following is a characteristic of normal urine?
It contains urea, ions, uric acid, and creatinine
What is the primary significance of the nephron's reabsorption process?
To conserve water and essential substances
What is the primary purpose of Table 7.3?
To illustrate the components of a healthy adult's urine
What is the significance of the variability of urine composition?
It means that Table 7.3 should only be used as a general guide
What is the purpose of including Table 7.3 in a study of the urinary system?
To illustrate the range of components found in healthy adult urine
What is the implication of the variability of urine composition for health professionals?
They should consider individual variations when interpreting urine composition
What is the significance of Table 7.3 in understanding the urinary system?
It provides a general guide to the components of healthy adult urine
Which part of the kidney is responsible for storing urine?
Renal pelvis
What is the primary location of the process of filtration in the kidney?
Glomerulus
Which of the following structures is NOT a part of the nephron?
Renal pelvis
Where does the process of reabsorption occur in the nephron?
Proximal convoluted tubule
What is the term for the process of draining urine from the nephrons?
Drainage
What percentage of water that enters the nephron is reabsorbed?
99%
What are the main materials that make up the urine, besides water?
Urea, ions, uric acid, and creatinine
What is normally absent from the urine?
Proteins
What is the primary component of urine, apart from water?
Urea
What is normally present in small amounts in the urine?
Glucose
What is the primary source of creatinine in the human body?
Breakdown of creatine phosphate in muscle
Which of the following foods is likely to be a natural source of purines?
Meat and fish
What is the energy-rich molecule that breaks down to produce creatinine in muscle?
Creatine phosphate
What is the significance of purines in the body?
They are waste products that need to be removed
What is the relationship between creatine phosphate and creatinine in muscle?
Creatine phosphate is broken down to produce creatinine
What is the primary function of the dissolved substances in normal urine?
To facilitate the excretion of waste products
What is the significance of the presence of bile pigments in urine?
It is responsible for the amber color of urine
What is the primary difference between the composition of urine and the filtrate in the glomerular capsule?
Urine has a higher concentration of water
What can be inferred about the process of urine formation from the composition of urine?
The kidneys are responsible for filtering waste products from the blood
What is the implication of the presence of various ions in urine for the body's overall function?
It is essential for maintaining proper pH levels in the body
What is the nature of the composition of urine in a healthy adult?
It is highly variable and should be used only as a guide
What is the significance of Table 7.3 in understanding the components of urine?
It serves as a guide to the components that may be present in urine
What is the implication of the variability of urine composition in a healthy adult?
It implies that the composition of urine should be used only as a rough guide
What is the purpose of understanding the components of urine in a healthy adult?
To understand the functioning of the kidneys
What is the relationship between the composition of urine and the functioning of the kidneys?
The composition of urine is a reflection of the functioning of the kidneys
What is the primary function of the renal pyramids in the kidney?
Storage of urine
Where does the process of reabsorption occur in the nephron?
Proximal convoluted tubule
What is the primary function of the renal capsule in the kidney?
Protection of the kidney from external damage
What is the term for the process of draining urine from the nephrons?
Drainage
In which part of the kidney does the process of filtration occur?
Glomerulus
Study Notes
The Production of Urine
- The formation of urine involves three major processes: glomerular filtration, selective reabsorption, and secretion by the tubules.
- Glomerular filtration is the first step, occurring in the renal corpuscle, where fluid is forced out of the blood and collected by the glomerular capsule.
Glomerular Filtration
- The process occurs due to high pressure in the glomerulus, caused by the afferent arteriole having a wider diameter than the efferent arteriole.
- The blood in the capillaries is separated from the cavity of the capsule by two single layers of thin, flat cells.
- Water and dissolved blood components are forced through the differentially permeable cell membranes and into the capsule, resulting in a filtrate.
- The filtrate contains water, salts, amino acids, fatty acids, glucose, urea, uric acid, creatinine, hormones, toxins, and various ions.
- About 20% of the plasma is filtered every minute, producing approximately 125 mL of filtrate per minute, or 180 L per day.
Reabsorption
- Many components of the filtrate are reabsorbed back into the blood in the peritubular capillaries.
- Reabsorbed substances include water, glucose, amino acids, and ions such as sodium, potassium, calcium, chloride, and bicarbonate.
- The process is active and under hormonal control, and can be regulated depending on the body's water requirements.
Tubular Secretion
- The third process involved in the formation of urine is tubular secretion, which adds materials to the filtrate from the blood.
- Substances secreted include potassium and hydrogen ions, creatinine, and drugs such as penicillin.
- Tubular secretion helps maintain blood pH and urine pH.
Composition of Urine
- Normal urine is a solution of water with dissolved wastes, such as urea and creatinine, and ions such as sodium, chloride, and potassium.
- Urine does not normally contain significant amounts of protein or glucose.
- The main materials making up urine, besides water, are urea, ions, uric acid, and creatinine.
The Kidneys and Excretion
- The kidneys are the principal excretory organs, maintaining the constant concentration of materials in the body fluids.
- The liver, lungs, sweat glands, and alimentary canal are also involved in processing and excreting waste materials.
- The kidneys, liver, lungs, sweat glands, and alimentary canal work together to process and excrete waste products, including nitrogenous wastes such as urea, uric acid, and creatinine.
This quiz covers the different organs involved in the excretion of waste products from the body, including the lungs, liver, and skin. It discusses the role of each organ in removing waste and maintaining homeostasis. Test your knowledge of the human excretory system!
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