Human Excretory Organs and Structure of Kidneys

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swiftie05

Cards (42)

  • Human Excretory Organs
    Kidney:
    A) water
    B) urea
    C) creatinine
  • Human Excretory Organs
    Skin
    A) Integumentry
    B) sweat
    C) sweat glands
  • Human Excretory Organs
    Lungs
    A) Respiratory
    B) carbon
    C) dioxide
    D) exhalation
  • Human Excretory Organs
    Large Intestine
    A) feces
  • Human Excretory Organs
    Liver
    A) ammonia
    B) kidneys
    C) bilirubin
    D) bile
    E) emulsification
  • Basic Processes in N waste Excretion/Urine Formation
    1. Filtration
    2. Reabsorption
    3. Secretion
    4. Excretion
  • Basic Processes in N waste Excretion/Urine Formation
    • Carried out by kidney in mammals
    > Upper renal cortex
    > Lower renal medulla
    • Blood flow
    > Renal artery
    > Renal vein
    • Renal pelvis
    > collects processed filtrate from kidney & transfers them to ureters
  • Basic Processes in N waste Excretion/Urine Formation
    Filtration
    •Solutes & water are filtered from blood into excretory tubule
    •Porous capillaries --> ions, salts, water filtered into tubule (filtrate)
    •Cells & proteins too large to be filtered; remain in blood
  • Basic Processes in N waste Excretion/Urine Formation
    Reabsorption
    •Recovering useful substances (water, solutes ex. vitamins, glucose, salts, hormones, amino acids) from filtrate in excretory tubule
    •Via active transport
    •Facilitated by transport epithelium
    > tissue lining which transport molecules from excretory tubule into
    blood vessel
  • Basic Processes in N waste Excretion/Urine Formation
    Secretion
    •Toxic substances and waste products from blood are added to
    filtrate by active transport
  • Basic Processes in N waste Excretion/Urine Formation
    Excretion
    •Unneeded substances released as urine
  • Structures of the Mammalian Kidneys: Nephron
    • Basic functional unit of kidney
    • Filters blood & forms filtrate
    • 2 types of nephrons:
    > Cortical nephrons
    > Juxtamedullary nephrons
  • 2 types of Nephrons
    Cortical nephrons
    • Shorter
    • Reach only short distance into medulla
    • 85% of nephrons
  • 2 types of Nephrons

    Juxtamedullary nephrons
    • Longer-limb
    • Extend deep into medulla
  • Structures of the Mammalian Kidneys: Nephron
    Filtration
    • Glomerulus
    > Ball of capillaries
    > Porous
    • Bowman’s capsule
    > Cup-shaped swelling encapsulated by glomerulus
    > Where small molecules are pushed from glomerulus forming a filtrate
  • Structures of the Mammalian Kidneys: Nephron
    Filtration
    • Filtrate processing
    • Proximal tubule
    • Loop of Henle
    • Descending limb
    • Ascending limb
    • Longer in juxtamedullary nephrons than in cortical nephrons
    • Connected to distal tubule
    • Functions:
    > Reabsorbs water
    >Forms concentrated urine
  • Structures of the Mammalian Kidneys: Blood Flow
    •Afferent arteriole
    > Branch of renal artery supplying blood to each nephron
    •Glomerulus
    •Efferent arteriole
    •Peritubular capillaries
    > Tangled with proximal & distal tubule
    > Some branches extend downward the renal medulla forming vasa recta
  • Urine Formation in the Kidney
    Filtration in the glomerulus
    ◦ Small molecules pass thru glomerulus
    > vitamins, amino acids, N wastes
    ◦ Collected in Bowman’s capsule
    ◦ Porous & permeable
    ◦ Same concentration of small molecules in blood plasma
  • Reabsorption, secretion in proximal tubule, loop of Henle, & distal tubule
    a) Reabsorption In Proximal Tubule
    b) Processes in descending limb of loop of Henle
    c) Processes in ascending limb of loop of Henle
    d) Processes in Distal Tubule
    e) Processes in Collecting Duct
  • Reabsorption In Proximal Tubule

    ◦ NaCl into renal cortex
    > Facilitated by transport epithelium lining proximal tubule
    ◦ Glucose thru co-transport mechanism with Na+
    ◦ H2O flows into renal cortex◦ Some ions from proximal tubule
    > ex. HCO3- for maintaining body pH
    ◦ Very small amounts of urea from proximal tubule
    ◦ Transport of reabsorbed water, salts, ions from kidney tissue into peritubular capillaries
    ◦ Secretion of some toxins & drug molecules from peritubular capillaries
  • Processes in descending limb of loop of Henle

    • H2O reabsorption from descending limb into renal
    cortex/medulla
    ◦ Facilitated by aquaporins
    ◦ Osmolarity of interstitial fluid increases
    • Filtrate becomes more concentrated as it goes down from renal
    cortex into medulla
    • Few ion & salt channels for reabsorption
    ◦ contributes to filtrate concentration
  • Processes in ascending limb of loop of Henle
    ◦ No aquaporins --> water impermeable
    ◦ Maintains concentration gradient for water reabsorption in descending limb
    > Thin segment: passive transport of NaCl
    > Thick segment: active transport of NaCl
    ◦ Filtrate becomes more dilute as it moves to renal cortex
    > Loses salt but not water
  • Processes in Distal Tubule
    Regulates K+ and Na+ concentration of body fluids
    ◦ Varies amount of K+ secreted & NaCl reabsorbed
    Contributes to pH regulation
    ◦ Regulates H+ secretion & HCO3- reabsorption
  • Processes in Collecting Duct
    Carries processed filtrate from distal tubule to renal pelvis
    • Water reabsorption when needed
    ◦ Dehydrated:
    > aquaporins appear in collecting duct
    > Water reabsorption without salt
    ◦ Enough water:
    > no aquaporins --> impermeable to water
    > Controlled by hormones
    > active transport of NaCl out of collecting duct
    • Urea reabsorption
    ◦ Contributes to osmolarity of renal medulla --> increases water reabsorption in descending limb
  • Kidneys conserve water
    1,200 mOsm/L urine osmolarity
    ◦ 4x more concentrated than blood (300mOsm/L)
    ~1,600 L of blood
    ◦ Amount of blood filtered by kidneys daily
    180 L fitrate
    ◦ 99% include essential solutes & water will be reabsorbed
    ~1.5L of urine daily
  • Waste Molecules from Urinary System
    • Nitrogenous wastes
    • Urea
    • Ammonium
    • Creatinine
  • Urea

    Primary N end product of amino acid metabolism
  • Ammonium

    1. Produced during amino acid breakdown in the liver
    2. Converted to urea since toxic
  • Creatinine

    • From metabolism of high-energy phosphate reserve in muscles
    • Part of the cycle that produces energy for muscle contraction
    • Amount in blood partially due to muscle mass (higher levels in men than women)
  • Waste removal

    • required for homeostasis
    1. Circulatory system transports wastes to kidneys
    2. Excreted through urethra
  • Sweat glands excrete a mixture of water, salt, & some urea
  • Blood Volume
    5 L of blood (1.3 gal) – average adult
    ◦ 8% of human body weight
    Blood components by volume
    ◦ ~44% RBCs
    ◦ ~55% plasma (water, ions, proteins, nutrients, wastes, gases)
    ◦ ~1% WBCs & platelets
  • Blood Volume
    Ions in blood:
    Na+, K+, HCO3-, Mg+, NaCl
    Important in maintaining blood volume; Attracts water
    Too much --> more water is reabsorbed --> increasing blood volume --> requires more effort from heart to pump blood -->
    increases pressure in arteries
    Lesser blood volume --> less blood pumped by heart --> less nutrients delivered to tissues -->low pressure in arteries -->
    low pressure in glomeruli filtration
    • Normal blood volume & pressure are important
  • Hormonal Mechanism to Control Blood Volume
    Juxtaglomerular apparatus (JGA)
    ◦ Made up of macula densa & juxtaglomerular cells
    ◦ Area where afferent arteriole comes in contact with distal tubule
    ◦ Controls rate of glomerular blood flow depending on factors
    > Hydration, blood volume, ion conc.
  • Juxtaglomerular apparatus (JGA)
    Macula densa cells
    ◦ Guard NaCl concentration in distal tubule fluid
    ◦ Stimulate juxtaglomerular cells to release renin in blood
    when NaCl is
    >lower NaCl--> lower blood volume, blood pressure
  • Renin-Angiotensin-Aldosterone System (RAAS)
    ◦ Renin (enzyme) --> series of reactions --> splitting of angiotensinogen
    (plasma protein) --> angiotensin II (peptide)
  • Renin-Angiotensin-Aldosterone System (RAAS)
    Angiotensin II
    ◦ Stimulates proximal tubule to increase Na+ & H2O reabsorption
    ◦ Triggers adrenal glands to release aldosterone
    ◦ Stimulates arteriole constriction (systemic effect) --> increase blood pressure --> decrease blood flow to capillaries in kidneys
    ◦ Prompts release of ADH (antidiuretic hormone) by pituitary gland
    ◦ Binds to hypothalamus --> stimulates thirst --> stimulates ADH release -->increase water uptake
  • Renin-Angiotensin-Aldosterone System (RAAS)
    Aldosterone:
    Reabsorption of high K+ & absorb high Na+ in distal tubule & collecting duct --> high water reabsorption --> high blood volume & pressure
  • Renin-Angiotensin-Aldosterone System
    (RAAS)
    • Negative feedback
    ◦higher blood pressure & blood volume to normal --> JGA cells stop renin release
    • Maintenance drugs which treat hypertension
    ◦ Block angiotensin II production
  • Antidiuretic hormone (ADH)

    • Stimulus:
    ◦ High blood osmolarity (ex. dehydration or salty food)
    • Effects:
    ◦ ADH secreted by hypothalamus --> posterior pituitary gland
    ◦ Distal tubule & collecting duct more water permeable --> increase aquaporins --> increase water diffuse from tubules to peritubular capillaries
    ◦ decreasing urine volume, water loss, blood osmolarity