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Balance in the Excretory System
Reabsoprtion and Secretion
100
What are kidneys? What is their function?
Fist sized, filters waste from the blood (excreted in urine) and adjusts the concentrations of salts in the blood
100
The filtration structure at the top of each nephron is a cap-like formation called the ____ ______. Within each capsule, a ___ ____ enters and splits into a fine network of capillaries called the _____.
- Bowman’s Capsule, renal artery, glomerulus.
100
What is the excretory system? What is its function?
-System that regulates the volume and composition of body fluids by excreting metabolic wastes and recycling some substances for reuse; main organs include kidneys, ureters, bladder, and urethra (URINARY SYSTEM)
100
The ability of the ___ to control blood __ is crucial to maintain an internal environment in which cell enzymes continue to function properly.
- kidneys, pH
100
What happens after the fluid is filtrated through the glomerulus?
- proceeds to the Bowman’s capsule
200
What is the renal pelvis?
Within each kidney, the mouth of its ureters flares open to form a funnel-like structure = THE RENAL PELVIS. Has cup-like extensions that receive urine from the renal tissues
200
What is glomerular filtration?
moves water and solutes, except proteins, from blood plasma into the nephrons
200
Define “waste” in the human body. Give examples.
-any substance that is produced by the body and is present in excess of the body’s needs. - examples: Carbon dioxide, water, sodium ions, chloride ions, hydrogen ions, and compounds that result from the breakdown of proteins and nucleic acids. Waste can pose as a threat to the body if it is accumulated.
200
What are osmoreceptors? What happens when blood plasma becomes too concentrated?
- are cells that are sensitive to osmotic pressure. Most osmoreceptors are located in the hypothalamus. The hypothalamus regulates mechanisms that enable the body to maintain homeostasis. When blood plasma become too concentrated, osmotic pressure increases. In response, osmoreceptors in the hypothalamus send impulses to the pituitary gland in the brain that causes the release of ADH.
200
What is a tubule? What does it absorb?
- The Bowman’s capsule is connected to a small, long, narrow tubule that is twisted back on itself to form a loop. This long, hairpin loop is a reabsorption device. Has three sections: proximal tubule, loop of Henle, and the distal tubule. - Like the small intestine, this tubule absorbs substances that are useful to the body such as glucose and a variety of ions, from the filtrate passing through. Unlike the small intestine, this tubule also secretes substances into the tissues surrounding it.
300
What are ureters? What is their function? What happens to urine after it travels through the ureters?
-Kidney’s release urine into two 28 cm long tubes called ureters. From ureters, the urine is moved by the peristaltic actions of smooth muscle tissue to the muscular urinary bladder. The bladder holds urine until excreted. The urethra (20cm long for males, 4cm long for women) is a tube that carries urine from the bladder where it then exits the body.
300
What is tubular reabsorption?
removes useful substances such as sodium from the filtrate and returns them into the blood for reuse by body systems
300
Explain how the glomerulus acts as a filtration device.
- The walls act as a filtration device. They are impermeable to proteins, other large molecules, and red blood cells, so these remain within the blood. Water, small molecules, ions, and urea (the main waste products of metabolism) pass through the walls and proceed further into the nephrons.
300
What is ADH? What is its role in the excretory system?
- is an antidiuretic hormone. Travels through the blood to the kidneys where it increases the permeability of the distal tubule and the collecting duct, allowing more water to be reabsorbed into the blood. This dilutes the blood and lowers osmotic pressure to normal.
300
Explain the recovery of substances in the proximal tubule.
- The cells of the proximal tubule are richly endowed with mitochondria, which use the energy-releasing power of ATP to drive the active transport of sodium ions, glucose, and other solutes back into the blood. Negatively charged ions tag along passively, attracted by the electrical charge on the transported ions. Water follows the ions by osmosis, it is reabsorbed into the blood flowing through the capillaries
400
What are the three regions the kidney are organized in?
- cortex, medulla, renal pelvis
400
What is tubular secretion?
- moves additional wastes and excess substances from the blood to the filtrate
400
Explain the processes involved in the Duct. - The tubule empties into a larger pipe-like channel called a ___ ___. The collecting duct functions as a ____ conservation device. The ____ that remains in the collecting duct is a suspension of water and various solutes and particles. It is now called ___. The solutes and water reclaimed during reabsorption are returned to the body via the renal ____.
- collecting duct, water, filtrate, urine, veins
400
How do the kidneys help maintain blood pH?
- Kidney’s excrete hydrogen ions and reabsorb carbonic acid as needed to maintain a normal blood pH. If the blood is too acidic, hydrogen ions are excreted and carbonic acid is reabsorbed. If the blood is too basic, hydrogen ions are not excreted and carbonic acid is not reabsorbed. Since urine is usually acidic, it follows that hydrogen ions are usually excreted.
400
What is the function of the loop of Henle?
- to reabsorb water and ions from the glomerular filtrate. In the descending loop of Henle, passive reabsorption of water by osmosis occurs. In the ascending loop on Henle, active reabsoprtion of sodium ions occurs and passive reabsorption of chloride and potassium ions occur.
500
What are nephrons?
-Microscopic tube-like filtration unit found in the kidneys that filters and reabsorbs various substances from the blood; produces urine.
500
What is water reabsorption?
- removes water from the filtrate and returns it to the blood for reuse by body systems.
500
What are 2 factors that contribute to filtration in the glomerulus?
- the permeability of the capillariesbof the glomerulus. Unlike capillaries in the rest of the body, capillaries of the glomerulus have many pores in their tissue walls. These pores are large enough to let in small molecules and water in the blood plasma to pass through, but small enough to not let proteins, red blood cells, and other large molecules in. - Blood pressure within the glomerulus is about 4 times greater than capillaries elsewhere in the body. The great rush of blood through the glomerulus provides that force for filtration.
500
How do the kidneys regulate salt balance?
- by controlling the excretion and reabsorption of various ions. A drop in sodium concentration is normally compensated by the kidneys under the influence of aldosterone. Aldosterone is a hormone that stimulates the distal tubules and collecting ducts to reabsorb sodium. Aldosterone also stimulates the secretion of potassium ions into the distal tubules and collecting ducts if the potassium concentrations in the blood is too high.
500
Explain reabsorption and secretion in the distal tubule. Explain reabsorption in the collecting duct.
- Reabsorption: active reabsorption of Na ions, passive reabsorption of negatively charged ions, and passive reabsorption of water by osmosis -Secretion: active secretion of H ions, and passive secretion of potassium ions by electrical attraction to chloride ions -Reabsorption in collecting duct: passive reabsorption of water by osmosis