EXCRETORY SYSTEM

PRESENTED BY

DAW AYE MON THET

ASSISTANT LECTURER

DEPARTMENT OF ZOOLOGY

UNIVERSITY OF MEDICINE ,MAGWAY

CHAPTER XI

EXCRETORY SYSTEM

Objective

1. Define the term excretion and describe how this process helps maintain homeostasis

2. Name the major metabolic wastes and the processes by which they are formed

3. Describe type of vertebrate kidney.

4. Explain the parts of urinary system and the process of urine formation.

As an organism carries out its life processes ,

- waste products build up in the body fluids

Life processes

• Respiration

• Feeding

• Sensitivity

• Movement

• Reproduction

• Growth

• Excretion

Waste product ( metabolic waste )

the products of metabolic activity

- after oxygen and nutrients have

been supplied to a cell

• If these metabolic wastes were not removed from the body

the organism would die

Therefore ,

the organism must be able to remove

- metabolic waste ( no use ) and

- other excess substances ( substances in excess of

requirements from organism )

that build up over time (= as time passes)

Excretion

- metabolic wastes and excess

substances are removed from the

organism

- also removes excess heat from the

body

helping to keep the temperature of

the body constant

EXCRETORY ORGANS

Skin

Liver Kidney

Lung

These organs work with - the circulatory system

- nervous system

- endocrine system

to keep the body’s internal environment constant

In other words ,

these organ systems maintain homeostasis

Major Metabolic Wastes

Excretory organs Metabolic wastes

1.Lungs Carbondioxide,Water(Cellular respiration)

2. Skin Water, Salts (Perspiration)

3. Liver Nitrogen Compounds(Ammonia,Urea,Uric acid)

4.Kidney Mineral salts(Sodium chloride and Potassium sulfate) and water (Urination)

• Many People confuse excretion with

elimination.

• Elimination, or defecation, is the removal from

the digestive tract of unabsorbed and

undigested food in the form of feces.

• Since these materials have never entered the

body cells, they are not metabolic wastes.

• Liver removes harmful substances,

• Such as bacteria,certain drugs,hormone

from the blood

• These substances are changed into inactive or less poisonous forms

• Purifies or detoxifies the blood

• Returned to blood stream

Finally excreted from the body by the kidney

Formation of Urea

Formation of urea

- Amino acids are the breakdown products of proteins.

- Because excess amino acids cannot be stored in the body, they are broken down in the liver.

- The parts of the amino acids are changed into other substances.

Amino acids Structure

- Because the ammonia produced from the amino group is very poisonous

- It is changed into the less harmful substance urea by a series of enzyme-catalyzed reactions.

- The urea diffuses from the liver into the blood stream.

- The bloodstream, then carries the urea to the kidneys.

- The kidneys filter urea from the blood, and

- It is finally excrete from the body in the urine

The Urinary System

Kidney

Ureter

Urinary bladder

Urethra

Filtration

Reabsorption

(Uriniferous tubules)

Filtration :

Renal corpuscle= (Bowman’s capsule & glomerulus)

Filtrates - water

glucose

amino acids

Various salts

Urea

Reabsorption

• Renal tubules

Types of vertebrate kidney

Types of vertebrate kidney

Types of kidney

1.Archinephros Embryo of cyclostomes

2. Pronephros Adult cyclostomes( lamprey , hagfish )Embryo of anamniotes ( frog, fish)

3. Mesonephros Adult Frog , Fish Embryo of amniotes

4.Metanephros Reptiles , Aves , Mammmals ( Amniotes )

Types of vertebrate kidney

- Vertebrate kidneys, or nephroi, are all built in accordance with a basic structural pattern consisting of

1.Glomeruli , usually incorporated in renal corpuscles;

2. Tubules, surrounded by peritubular capillaries and

3. A pair of longitudinal ducts.

Variations in the details from fish to man are primarily in - the number and arrangement of glomeruli

and - the relative length of the tubules.

In present –day vertebrates

- The uriniferous tubules develop

antero-posteriorly in two or three stages

- In succession these stages are

pronephros

mesonephros evolved from the

metanephros original archinephros

Pronephros

Pronephros

Pronephric duct

Segmental nephron

are

Uriniferous tubules - open into a common pronephric duct

- runs backward to enter

the embryonic cloaca

Uriniferous tubules - open into a

common

pronephric duct

- runs backward to

enter

the embryonic cloaca

- A pair of pronephroi become functional only

in some cyclostomes and embryos of all

anamniote

- In other vertebrates ,they degenerate during

development.

Mesonephros

Mesonephros

- develops from that part of the nephrotome which lies

behind the pronephros.

At First- consists of paired segmental uriniferous tubules,

- each with a peritoneal funnel opening into the coelom,

and a glomerulus enclosed in a Bowman’s capsule.

- Mesonephric uriniferous tubules

join the existing pronephric duct

on each side, called mesonephric duct

or Wolffian duct

Later

Mesonephric tubules undergo budding to form hundreds of tubules

- their segmental arrangement is lost

- the later tubules have no peritoneal funnels.

- form the adult functional kidneys in some

fishes and amphibians

-form the embryos of amniotes,degenerate

in the adult

Metanephros

Metanephros

• The first embryonic hint of a metanephros is the formation the metanephric duct that appear as a ureteric diverticulum arising at the base of the preexisting mesonephric duct.

The ureteric diverticulum grows dorsally into the posterior region of the nephric ridge.

-Here it enlarges and stimulates the growth of metanephrictubules that come to make up the metanephric kidney .

The metanephros- becomes the adult kidney of amniotes and

the metanephric duct is called the ureter.