Excretion

• What is excretion?


  Excretion is the biological process of removing waste products from metabolism to maintain homeostasis and prevent toxic buildup in organisms.
• What are the main types of waste products excreted by living organisms?


  The main types include carbon dioxide (from respiration), urea (from protein metabolism), and excess salts and water.
• What role does excretion play in maintaining homeostasis?


  Excretion regulates the internal environment of the body by balancing water, salts, and eliminating toxic substances, which is crucial for cellular function.
• How do plants excrete waste products?


  Plants excrete waste through processes like transpiration (loss of water vapor) and diffusion of gases (like oxygen and carbon dioxide) through stomata.
• What are stomata, and what is their role in plant excretion?


  Stomata are small openings on the surfaces of leaves that allow for gas exchange (oxygen and carbon dioxide) and help regulate water loss.
• What is the primary organ of excretion in humans?


  The primary organs are the kidneys, which filter blood and produce urine to eliminate waste
• Describe the structure of the kidney.


  The kidney consists of an outer cortex, an inner medulla, and a renal pelvis, which collects urine before it moves to the ureter.
• What is the nephron?


  The nephron is the functional unit of the kidney, responsible for filtering blood and forming urine.
• List the main parts of a nephron.

  The main parts are the Bowman's capsule, glomerulus, proximal convoluted tubule, Loop of Henlé, distal convoluted tubule, and collecting duct
• What is the process of ultrafiltration?


  Ultrafiltration occurs in the glomerulus, where high blood pressure forces water and small solutes (like urea and glucose) from blood into the Bowman's capsule.
• What is selective reabsorption in the nephron?


  Selective reabsorption is the process where useful substances (like glucose and certain ions) are reabsorbed from the filtrate back into the blood, primarily in the proximal convoluted tubule.
• How is glucose reabsorbed in the nephron?


  Glucose is reabsorbed through active transport mechanisms in the proximal convoluted tubule, ensuring it returns to the bloodstream.
• What happens during the Loop of Henlé?


  The Loop of Henlé creates a concentration gradient in the medulla, allowing for the reabsorption of water and salts, which helps concentrate urine.
• What role does the distal convoluted tubule play in excretion?


  The distal convoluted tubule further adjusts the composition of urine by reabsorbing more ions and water, regulated by hormones like aldosterone.
• What is the function of the collecting duct?


  The collecting duct is where final water reabsorption occurs, influenced by antidiuretic hormone (ADH), affecting urine concentration.
• How does antidiuretic hormone (ADH) affect kidney function?


  ADH increases the permeability of the collecting duct, allowing more water to be reabsorbed, resulting in concentrated urine when hydration levels are low.
• What is the composition of urine?

  Urine primarily consists of water (about 95%), urea, creatinine, uric acid, various ions (like sodium and potassium), and small amounts of other substances.
• What are the ureters, and what is their function?


  Ureters are tubes that transport urine from the kidneys to the bladder, using peristaltic movements to facilitate flow.
• What is the role of the bladder in excretion?


  The bladder stores urine until it is excreted from the body, with stretch receptors signaling when it is full.
• What are the effects of dehydration on urine production?


  Dehydration leads to increased ADH release, resulting in more water reabsorption and concentrated urine, while low fluid intake can lead to dark yellow urine.