Chapter 36

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Transcript Chapter 36

Chapter 36:

pp. 665 - 678

Body Fluid Regulation & Excretory Systems

BIOLOGY

10th Edition

Outline

 Body Fluid Regulation  Aquatic Animals  Marine Bony Fish  Freshwater Bony Fish  Terrestrial Animals  Nitrogenous Waste Products  Organs of Excretion  Urinary System in Humans  Kidneys  Urine

Nitrogenous Waste Products

 Catabolism of amino acids and nucleic acids results in ammonia   High solubility permits it to be excreted directly by many aquatic animals Terrestrial animals must convert ammonia to urea or uric acid  Urea causes loss of much water per unit of nitrogen  Mammals and amphibians  Must drink lots of water  Uric acid requires much less water per unit of nitrogen excreted  Reptiles, birds, and arthropods   Require much less water than mammals and amphibians Allows invasion of drier habitats far from standing water

Nitrogenous Wastes

proteins amino acids NH 2 most fishes and other aquatic animals adult amphibians, sharks, and mammals Insects, birds, and reptiles ammonia H N H H H 2 N urea O C NH 2 O HN C uric acid O C N H C C H N C N H O water needed to excrete energy needed to produce 4

Organs of Excretion in Invertebrates

 Most animals have tubular excretory organs  Regulate the water-salt balance of the body  Excrete metabolic wastes into the environment  Flame Cells in Planarians  Nephridia in Earthworms  Malpighian Tubules in Insects

Excretory Organs in Animals

flame cell excretory tubule fluid filtering into flame cell a.

flame cell nucleus cilia excretory pore excretory tubule Flame-cell excretory system in planarians capillary network tubule bladder septum entrance of nephridiostome pore b.

Earthworm nephridium 6

Body Fluid Regulation

 An excretory system regulate body fluid concentrations  Dependent upon concentration of mineral ions such as sodium and potassium  Water can enter the body through:  Drink  Food  Metabolism

Body Fluid Regulation

 Water tends to move into the region with the lowest water concentration  A marine environment  High in dissolved salts  Tends to promote the osmotic loss of water, and  The gain of ions by drinking water  Marine invertebrates nearly isotonic to seawater  Blood of cartilaginous fishes contains enough urea to match the tonicity of sea water  Fresh water environment  Tends to promote a gain of water by osmosis, and  A loss of ions as excess water is excreted

Aquatic Animals

 Bony Fishes  Body fluids of bony fishes with only moderate amount of salt  Marine bony fishes  Body fluids hypotonic to sea water  Passively

lose

water through gills  Must constantly drink seawater to compensate  Excess salt ions actively transported back into seawater through the gills  Freshwater bony fishes have opposite problem  Body fluids hypertonic to fresh water  Passively

gain

water through gills  Eliminate excess water through copious hypotonic urine

Body Fluid Regulation in Bony Fishes

passive loss of water through gills drinks seawater a. Marine bony fish salts actively excreted by gills does not drink passive gain of water through gills scanty amount of isotonic urine contains some salts salts actively taken up by gills b. Freshwater bony fish large amounts of hypotonic urine contain few salts 10

Osmoregulation in a Shark

Terrestrial Animals



Terrestrial animals lose water through excretion and respiration



Must drink water to make up for loss

 Some reduce excretory loss by excreting nitrogen as relatively insoluble uric acid  Certain animals also have a highly convoluted nasal passage with a mucous membrane surface

Adaptations of a Kangaroo Rat to a Dry Environment

Exhaled air is cooled and dried in long convoluted air passages.

Animal fur prevents evaporative loss of water at skin.

Urine is the most hypertonic known among animals.

Oxidation of food results in metabolic water.

Fecal pellets are dry.

Adaptations of Marine Birds to a High Salt Environment

salt solution exits here salt solution runs down beak here

Urinary System in Humans



Human kidneys

 Located on either side of vertebral column, just below the diaphragm  Each connected to a ureter  Conducts urine from the kidney to the urinary bladder  Urine voided through urethra  Tube between bladder and exit

The Human Urinary System

renal artery renal vein aorta inferior vena cava 1. Kidneys produce urine.

2. Ureters transport urine.

3. Urinary bladder stores urine.

4. Urethra passes urine to outside.

Kidneys

 Renal cortex  Outer region  Granular appearance  Renal medulla  Cone-shaped renal pyramids  Renal pelvis  Hollow-chambered innermost part of the kidney

Animation

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Macroscopic & Microscopic Anatomy of the Kidney

nephrons renal pelvis renal cortex renal medulla ureter renal artery and vein a. Gross anatomy renal pyramid in renal medulla renal pelvis b. Two nephrons collecting duct 19

Nephrons



Each kidney composed of many tubular nephrons



Each nephron composed of several parts

 Glomerular capsule  Glomerulus  Proximal convoluted tubule  Loop of the nephron  Distal convoluted tube  Collecting duct

Nephron Anatomy

Renal Cortex glomerular capsule (Bowman's capsule) glomerulus efferent arteriole proximal convoluted tubule

peritubular capillary distal convoluted tubule afferent arteriole efferent arteriole glomerulus b. Surface view of glomerulus and its blood supply afferent arteriole distal convoluted tubule microvilli proximal convoluted tubule venule c. Cross sections of proximal and distal convoluted tubules 20 µm renal artery renal vein peritubular capillary network ascending limb descending limb collecting duct Loop of the nephron (loop of Henle) descending limb ascending limb capillaries collecting duct Renal Medulla d. Cross sections of a loop of nephron limbs and collecting duct. (The other cross sections are 10 µm a. Anephron and its blood supply those of capillaries.)

b: © R.G. Kessel and R H. Kardon, Tissues and Organs: A Text-Atlas of Scanning Electron Microscopy. W. H. Freeman & Co., San Francisco 1979; c, d: Journal of Ultrastructure Research by Maunsbach, Arvid B. Copyright 1966 by Elsevier Science & Technology Journals. Reproduced with permission of Elsevier Science & Technology Journals in the format Textbook via Copyright Clearance Center

Proximal Convoluted Tubule

peritubular capillary proximal convoluted tubule cell lumen microvilli mitochondrion nucleus 500 × b.

Urine Formation



Urine production requires three distinct processes:

 Glomerular filtration in glomerular capsule  Tubular reabsorption at the proximal convoluted tubule  Tubular secretion at the distal convoluted tubule

Processes in Urine Formation

renal artery

glomerular capsule H 2 O urea glucose amino acids uric acid salts glomerulus efferent arteriole Glomerular Filtration Water, salts, nutrient molecules, and waste molecules move from the glomerulus to the inside of the glomerular capsule. These small molecules are called the glomerular filtrate.

proximal convoluted tubule Tubular Reabsorption Nutrient and salt molecules are actively reabsorbed from the convoluted tubules into the peritubular capillary network, and water flows passively.

Tubular Secretion Certain molecules (e.g., H convoluted tubules.

+ and penicillin) are actively secreted from the peritubular capillary network into the afferent arteriole distal convoluted tubule renal vein venule loop of the nephron collecting duct peritubular capillary network H 2 O urea uric acid salts NH 4 + creatinine 24

Animation

Reabsorption of Salt and Water

C1 Na + H 2 O Renal cortex Outer medulla H 2 O descending limb H 2 O Na + C1 Inner medulla loop of the nephron ascending limb H 2 O Urea H 2 O collecting duct 26

Urine Formation and Homeostasis

 Excretion of hypertonic urine  Dependent upon the reabsorption of water  Absorbed from  Loop of the nephron, and  The collecting duct  Osmotic gradient within the renal medulla causes water to leave the descending limb along its entire length  Antidiuretic hormone (ADH)  Plays a role in water reabsorption  Released by the posterior lobe of the pituitary

The Renin-Angiotensin-Aldosterone System

blood vessel

kidneys liver adrenal cortex secretes angiotensinogen secrete renin speeds angiotensin I stimulates angiotensin II secretes aldosterone 28

Maintenance of pH and Osmolality

 More than 99% of sodium filtered at glomerulus is returned to blood at the distal convoluted tubule  Reabsorption of sodium regulated by hormones  Aldosterone  Renin  Atrial Natriuretic Hormone (ANH)  pH adjusted by either  The reabsorption of the bicarbonate ions, or  The secretion of hydrogen ions