Glormeruli- Filter in kidneys that have a tuft of capillaries

Homeostatic Control

• Osmoregulation

  • Osmosis- water diffuse across a selectively permeable membrane from high to lower water concentration

    • Osmolarity- 300 mOsm/L

    • Hyperosmotic- higher osmolarity (low salt concentration)

    • Isosmotic- normal salt concentration

    • Hypoosmotic- lower osmolarity (higher salt concentration)

• Osmoconformers- osmolarity of cellular and extracellular solutions match the environment. Ex. Marine invertebrates

• Osmoregulators- uses controls systems to keep osmolarity of cellular and extracellular fluids the same. Ex. Humans, freshwater invertebrates→ must expend energy to excrete excess water to keep their internal fluids hyperosmotic to their surroundings

Tubules formed by transport epithelium carries out excretion and osmoregulation. Transport proteins move molecules and iOS in and out of tubule via active/passive transport.

• Tubule Function

1. Filtration- what do we keep? What needs to go?

2. Tubular reabsorption- reabsorbs things we may need

3. Tubular secretion- selective process in which molecules and ions are transported from ECF and blood into tubules

4. Excretion- fluid containing waste materials released.

• Excretion

  • Nitrogenous wastes:

    • Ammonia- fish

    • Urea- all mammals. Has to be diluted. No dilution= kidney stone

    • Uric acid- birds. Four nitrogens in one molecule (conserves water)

• Invertebrate osmoregulators specialized tubules

  • Protonephridia- flatworms

    • Branches end with a flame cell containing cilia that moves fluid through tubule

    • Hemolymph passes though protonephridia and some molecules are absorbed, Nitrogenous wastes are secreted into tubules

    • Urine released through pores

    • ATP needed to beat the cilia

    • Flame cell→ filtration and keeps volume balance.

    • 

    • Metanephridia- earthworm

      • Segments of worm= separate compartments

      • The openings of the metanephridia takes the ICF from the segment in front of it.

    

    • Absorption and secretion

    • Malpighian tubules

      • Tissue that extends of digestion system.

      • Tubules secreted K into lumen of proximal segment which draws Cl- for hemolymph. Salt gradient.

      • Because salt is in there water enters and dilutes it

      • Eat→absorbed via digestion system→mapighian tubules→ K+ and Cl- are reabsorbed and water and uric acid is released

        

      • Mammals!

        • Excretory Tubules→ nephrons in kidneys

        • Renal artery→ carries blood into kidney. Filtered blood leaves the kidney by the renal vein

        • Peritubular capillaries→ reabsorb molecules and ions from filtrate

          • Urine: Collecting ducts→ renal pelvis→ ureter→ urinary bladder→ urethra

            

            

          • Kidney: outer renal cortex and central renal medulla

          • Nephrons go from outer cortex down to medulla and then back up

          • Glomerulus- when circulatory meets urinary system

          • Nephron

            • Renal Corpuscle- Bowman’s capsule and glomerulus and first portion of nephron.

              • Afferent arteriole delievers blood to glomerulus. Efferent arteriole is smaller than afferent→maintains high capillary pressure

            • Proximal Tubule- reabsorption

              • Na/K pumps move Na and K into ICF surrounding tubule

            • Loop of Henle- ascending arm and descending arm. Establishes strong osmotic gradient in the tissues outside the loop.osmolarity increases

              • Descending: The walls of the loop will get more concentrated. The membrane is only permeable to water. As you go down, it will get a higher and higher osmolarity, so water will leave. Filtrate starts to get more concentrated because osmolarity outside is getting stronger and stronger (more and more water wants to leave.) Water goes back into blood at the vessel network.

              • Ascending: (secretion to fix gradient) Now we go back through gradient. Concentration inside tube > concentration outside. No water movement, only salt.

                • Pump shows up at around 400mOsm inside and 600mOsm outside to push salt out. Requires energy.

                • Dilutes considerably

            • Distal Convoluted Tubule- secretion and reabsorption

              • Last opportunity to take stuff back or push stuff out. Communicating with the rest of the body!

              • Hormonal control comes in and influences.

              • H2O recovered by osmosis in response to hormones triggered by changes in body’s salt concentration.

              • K+ and H+ are secreted into fluid and Na+ and Cl- are reabsorbed.

            • Collecting Duct- excretion

              • Antidiuretic Hormone

              • Permeable to water

              • Salt concentration increases as descends.

              • Passive urea transporters near the bottom contribute to gradient.

            • Dark urine- high ADH, retains water

Regulation

• Vascular control of blood pressure

• Juxtaglomerular complex- two set of cells.

  • Juxaglomerlar cells- by glomerulus monitors pressure and (osmolarity) salt levels in.

  • A rise in BP→ increase filtration rate. Receptors release hormones that constrict afferent arteriole and dilates efferent ( lowers GFR)

  • A drop in BP→ receptors dilate arteriole and constricts efferent (GFR rises)

  • In distal convoluted tubule,

    • Macula Densa- Monitors salt level out

• RAAS - Renin-angiotensin-aldosterone System

  • Responds when reduced NaCl and ECF volume, reduced arteriol blood pressure

  • The juxtaglomerular apparatus releases Renin into blood

  • Renin cleaves angiotensinogen to make angiotensin I

  • Angiotensin converting enzyme (ACE) converts angiotensin I to angiotensin II

    • Responds when reduced sodium delivery to the DCT detected by macula densa cells and excess Na is excreted.

    • Angiotensin II

      • will talk to adrenal gland which makes aldosterone→ increase Na reabsorption→ conserved H20

      • Will cause arteriolar constriction to increase BP

      • Trigger ADH to trigger thirst to increase fluid intake

        Kidney Function in nonmammalian vertebrates

        • Maine teleosts continually lose H2O to their environments because of osmosis. Have to drink lots

        • Gil tissue (saltwater)

          • High salt in media that want to move into organism. Tissue, increased salt.

        • Osmolarity imbalance: more salt outside organism, H2O leaves to dilute ocean.

          • Compensate by drinking lots of water And pump

            • Pump at gill pushes salt right back out

              Gil tissue (freshwater)

            • Now fish is gonna be really concentrated compared to water. Water gained by osmosis in tissue. Fish don’t drink eater, they just funnel through gills, excrete lots of water.

            • Salt is pushed out From across the gills

    • Sharks and Rays- conformers

      • Maintain osmolarity by retaining urea and TMAO trimethylamine oxide

      • They can offload excess salt through digestive system

    • Terrestrial Amphibians, reptiles, and birds

      • Secrete N waste in uric acid crystals

      • Reptiles and birds take in lots of salt water→ secrete excess through salt glands in head

    • Water conservation in terrrestrial mammals→ length of henle. Longer= more conservation