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Biology 20. Excretion General, Structure & Function, Four Steps to Urine Formation Hormones, Composition of Urine. Introduction. Humans are 70% water 1/3 of this is in plasma Blood – carries nutrients, picks up waste Wastes need to be removed

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biology 20

Biology 20

Excretion

General, Structure & Function,

Four Steps to Urine Formation

Hormones, Composition of Urine

introduction
Introduction
  • Humans are 70% water
    • 1/3 of this is in plasma
  • Blood – carries nutrients, picks up waste
  • Wastes need to be removed
  • Composition of fluids need to be kept in balance
  • Excretion: monitor, analyze, select, reject
excretion
EXCRETION
  • Excretion is the process of removing metabolic wastes from the body.
  • During the metabolic processes of the body, wasteproducts are removed from the site of production by the blood.
  • As these wastes accumulate, the kidney removes them from the blood and excretes them to the environment.
  • The excretory product becomes urine.
excretion1
Excretion
  • Process of removing cellular waste
  • Balance pH of blood
  • Maintain water balance
  • Happens in Kidney
functions of the excretory system
FUNCTIONS OF THE EXCRETORY SYSTEM
  • Functions:
  • To maintain homeostasis
  • Regulates and stabilise the internal environment by controlling 4 groups of chemicals
    • Water:
    • Excretion of metabolic wastes: Elimination of poisonous by-products of chemical reactions:
    • Osmoregulationfluid and salt regulation: regulation of hydrogen, sodium, potassium, calcium, chloride ions:
    • Regulation of body fluid composition: Removal of essential nutrients that dangerous in excess:
waste products
WASTE PRODUCTS
  • The principle metabolic wastes in most animals are:
    • Carbon Dioxide – is excreted through the respiratory surfaces
    • Water – excreted through respiratory surfaces, skin as sweat as well as kidneys
    • Nitrogenous Wastes – products of protein and nucleicacid digestion
waste products1
Waste Products

Carbon

Dioxide

Water

Nitrogen

Wastes

nitrogenous wastes
NITROGENOUS WASTES
  • Ammonia – The first metabolic product of amino acid deamination – hydrolysis (protein digestion)
    • highly toxic
    • cannot accumulate in body
    • must be converted into less toxic uric acid and urea
  • Uric Acid – produced from ammonia
    • not very soluble – can be excreted as a paste with little water loss
    • non - toxic
deamination urea
Deamination & Urea
  • Proteins – contain a nitrogen molecule
    • Amino acid – building blocks of protein
      • Nitrogenous base
  • Removal of N and H
  • Occurs in the liver
  • Byproduct – ammonia
    • Toxic substance
  • Ammonia combines with CO2 to form urea
  • Urea –less toxic
  • Uric acid – waste product from the breakdown of nucleic acids (DNA)
nitrogenous wastes1
NITROGENOUS WASTES
  • Urea – converted from ammonia
    • less toxic than ammonia
    • produced in the liver
    • can be excreted in concentrated form
    • requires more water to excrete than uric acid
slide12

1. Vena cava

2.Right Kidney

3. Ureter

4. Bladder

5. Urethra

6. Aorta

7. Left Kidney

8. Renal Vein

9. Renal Artery

slide13

Urinary System

Adrenal gland

Kidney

Ureters

Bladder

Urethra

slide14
ORGAN: Function
  • Kidney: site of blood filtration
  • Renal artery: brings blood to kidney
  • Renal vein: brings blood back to heart
  • Ureter: Brings waste TObladder
  • Bladder: Temporary urine storage site
  • Urethra: Brings waste FROM bladder, out of system
the kidney

Structure

Function

Cortex

Outer layer

Where filtration occurs

Medulla

Inner area

Water reabsorption

Renal Pelvis

Collects waste

Joins kidney to ureter

The Kidney
structure and function of kidney
STRUCTURE AND FUNCTION OF KIDNEY
  • Three distinct regions of the kidney
    • Cortex – outer region
    • Medulla – just below cortex
    • Pelvis – a hollow chamber within the medulla
  • The cortex and medulla of each kidney are made up of a approximately one millionnephrons
the kidney1

Renal Cortex

The Kidney

Renal Medulla

Renal Pelvis

Ureter

Nephrons

Renal Artery

Renal Vein

structure and function of kidney1
STRUCTURE AND FUNCTION OF KIDNEY
  • NEPHRON
    • the structural and functional unit of the kidney
label the following diagram
Label the following diagram

Bowman’s Capsule

Glomerulus

Renal artery

Distal tubule

Proximal tubule

Renal vein

Collecting duct

Capillary bed

Loop of Henle

slide21

STRUCTURE

FUNCTION

Afferent arteriole

Brings blood to glomerulus

Efferent Arteriole

Leaves glomerulus, goes to vein

Glomerulus

Ball of capillaries – site of filtration

Bowman’s Capsule

Filter

Proximal Tubule

First tube in nephron. From BC. Reabsorption of Water

Distal Tubule

Leads to collecting duct

Collecting duct

Empties waste into renal pelvis

Renal pelvis

Collecting site for all nephrons – waste out to ureter

structure and function of kidney2
NEPHRON

the structural and functional unit of the kidney

BOWMAN’SCAPSULE

a double walled chamber – start of the tubule.

STRUCTURE AND FUNCTION OF KIDNEY
the nephron
The Nephron

Bowman's

Capsule

structure and function of kidney3
GLOMERULUS

network of capillaries within the Bowman’s capsule

high pressure (4x higher than in capillaries)

STRUCTURE AND FUNCTION OF KIDNEY
the nephron1
The Nephron

Bowman's

Capsule

Glomerulus

The Nephron

structure and function of kidney4
STRUCTURE AND FUNCTION OF KIDNEY
  • PROXIMAL TUBULE
    • active transport of many valuable substances back into blood network
      • glucose
      • amino acids
      • sodium
the nephron2
The Nephron

Proximal

Convoluted

Tubule

structure and function of kidney5
STRUCTURE AND FUNCTION OF KIDNEY
  • PROXIMAL TUBULE
  • What doesn’t get absorbed?
    • urea
    • other toxic substances
    • some salt
    • much of the water
structure and function of kidney6
STRUCTURE AND FUNCTION OF KIDNEY
  • LOOP OF HENLE
    • the long hair-pin turn!!
the nephron3
The Nephron

Loop of

Henle

structure and function of kidney7
LOOP OF HENLE

the long hair-pin turn!!

some of the remaining water and salt will be returned to the blood

lies in the medulla which is relatively salty (hypertonic)

STRUCTURE AND FUNCTION OF KIDNEY
structure and function of kidney8
STRUCTURE AND FUNCTION OF KIDNEY
  • DISTAL TUBULE and COLLECTING DUCTS
the nephron4
The Nephron

Distal

Convoluted

Tubule

the nephron5
The Nephron

Collecting

Duct

structure and function of kidney9
STRUCTURE AND FUNCTION OF KIDNEY
  • DISTAL TUBULE and COLLECTING DUCTS
    • More water reabsorption
      • This depends on the presence of certain hormones
      • (ADH) Anti diuretic Hormone
    • Exact amounts of substances are reclaimed to the blood
      • very precise
urine formation
Urine Formation
  • Depends on three functions:
    • Filtration
      • Movement from blood – Bowman’s capsule
    • Reabsorption
      • Transfer of needed nutrient back INTO blood
      • Tubules
    • Secretion
      • Movement of material from blood back into nephron
four steps to urine formation
Four Steps to Urine Formation

1)FILTRATION

  • Occurs at the junction of the glomerulus and the wall of the Bowman’s capsule
  • Each glomerulus receives blood from an afferent arteriole and discharges its blood into an efferent arteriole (hypertonic).
  • Fluid and dissolved materials (nutrients, wastes, ions) in the blood plasma pass from the glomerulus into Bowman’s capsule
    • due to a local increase in blood pressure within the glomerulus
four steps to urine formation1
Four Steps to Urine Formation

1) Filtration (con’t)

  • this material is then called nephric filtrate
  • blood cells, plasma proteins and platelets are too large to pass through the wall of the capillary and therefore remain within the capillary.
four steps to urine formation2
Four Steps to Urine Formation

2) REABSORPTION

  • in the proximal tubule
  • returns about 99% of filtrate to the blood
  • efferent arteriole feeds second capillary network that surrounds the tubule
  • this network receives reabsorbed substances
    • eventually leads to renal vein
four steps to urine formation3
Four Steps to Urine Formation

2) REABSORPTION (con’t)

  • Water rushes into the blood because of osmosis

Problem

  • Not enough water is returned this way.

Solution

  • Just actively transport water into the blood right?
wrong

Wrong!!!

There is no way of ACTIVELY transporting water

So how can we transport more water into the blood?

solution
Solution

2) Reabsorption (con’t)

  • active transport of solutes into the capillary bed
    • glucose
    • amino acids
    • vitamins
    • inorganic ions (Na+)
  • water is passively reabsorbed from the proximal tubule as these solutes are actively removed from the filtrate
four steps to urine formation4
Four Steps to Urine Formation

2) Reabsorption (con’t)

  • Reabsorption and the distal tubule.
    • A more selective, precisely regulated reabsorption occurs in the distal tubules
    • Additional quantities of salts and water may be reabsorbed
    • The exact amount of each substance reclaimed occurs in the distal tubules.
    • excess is excreted in urine
      • e.g. glucose and diabetes
four steps to urine formation5
Four Steps to Urine Formation

3) SECRETION

  • This is the last chance for anything to leave the blood and enter the urine
  • Active transport
  • Occurs in the distal tubule and collecting duct
  • Hydrogen ion secretion – helps regulate blood pH
    • Distal tubule
    • Na+ moves into the blood and H+ moves into the tubule filtrate
      • blood pH increases (ranges 7.3 - 7.4)
      • urine pH decreases (ranges 4.5 - 8.5)
four steps to urine formation6
Four Steps to Urine Formation
  • potassium secretion
    • prevents accumulation of potassium that can create neural and muscular problems
  • some drugs are removed from the body by secretion
  • substances eliminated in this manner are
    • creatine – by product of protein metabolism
    • potassium
    • penicillin
four steps to urine formation7
Four Steps to Urine Formation

4) Elimination

  • Pathway
    • collecting duct
    • renal pelvis
    • ureter
    • urinary bladder
    • urethra
    • environment
slide48

Nephron Function Summary

NH

3

+

K

Reabsorption

CORTEX

Amino

Acids

Na

Water

Glucose

Water

Secretion

Na

Filtration

Na

Water

Na

Water

Na

Water

Na

ADH

Na

Water

MEDULLA

Na

Active Transport

Water

Water

Passive Transport

what is in urine
What is in urine?
  • Excess sugars
  • Excess salts
  • Excess H+ ions
  • Urea and uric acid
  • Excess H2O
hormones
HORMONES
  • ADH
  • The Antidiuretic hormone
    • influences the RATE of water reabsorption into blood from collecting ducts
    • released by the pituitary gland in the brain
  • Osmoreceptors in brain stimulated by low blood volume and increased osmotic pressure
    • both of those means that there is not enough water in the blood.
    • rate of ADH secretion is increased. ADH saves water.
    • More ADH = more H2O absorption = increased urine concentration
    • Very yellow concentrated urine
slide53
Most water reabsorbed in proximal tubule
    • permeable
  • Rest of tubule permeable ONLY IF ADH is present
    • Ascending loop
    • Distal tubule
aldosterone and sodium
Aldosterone and Sodium
  • Aldosterone – hormone
    • Produced in adrenal gland
    • Increased Na+ uptake in nephron
    • More water may also move out
      • Osmosis (high to low)
  • Blood pressure
    • Less fluid – lower blood pressure
slide55
Angiotensin produced
    • Constricts blood vessels, increase blood pressure
    • Causes release of aldosterone
  • Aldosterone acts on distal tubule and collecting duct
    • More sodium reabsorbed
    • Fluid level increase
    • BP increases
kidney disease
Kidney Disease
  • Diabetes Insipidus
    • Problems with ADH production
    • No ADH, no H2O reabsorption
    • Huge urine output
      • Up to 20 L/day
slide58
Kidney Stones
    • Minerals forming solid crystals (Ca+, Na+)
    • Get lodged in pelvis or ureter
    • Can tear tissues as it moves out
    • OHMYGOODNESSMAKEITSTOPICANNOTSTANDTHEPAIN!!!!!!!!!!!!!!!!
  • Stone removal
    • Surgery
    • Ultrasound
    • catheter
slide60
Kidney Dialysis
    • Cleaning of blood
    • Treatment of kidney failure
    • Blood goes through a filter
    • Concentration gradients remove waste
slide63
Kidney Donation
    • Human system built in twos
    • Extra kidney for backup
    • One kidney – can do all the work
    • With less than 20% kidney function, problems occur
      • Requires kidney dialysis
    • If problem gets really bad, might need a new one  TRANSPLANT