Excretion Ureotelism Nephron
Excretion
As a result of continuous synthesis and breakdown of materials many
waste products are formed in cells. The process by which the cellular
nitrogenous wastes are eliminated is called excretion.
Three main nitrogenous wastes are ammonia, urea and uricacid. Various vertebrates excrete different form of nitrogenous wastes, according to the nature of their habitat and availability of water.
Ureotelism
Ureotelism is an adaptation for a semi-terrestrial habitat. Urea
requires only a small quantity of water to form urine and never involves much
water loss; Further, urea is much less toxic than ammonia and it can be
retained in blood for sometime before it is transported and eliminated through
the excretory organs. Though the concentration of urea in the blood is small,
it can be stored safely in the bladder in high concentration. Thus ureotelism is
conditioned by the shortage of water, characteristic of the terrestrial habitat.
Urea Biosynthesis (Ornithine Cycle)
Liver is the principal organ of urea biosynthesis. In the ornithine cycle,
ammonia, formed by deamination in cells and tissues, combines with carbon
dioxide to form carbamyl phosphate. This compound is subjected to a cyclic chemical reactions as provided in the figure. Three molecules of ATP are
spent to convert the toxic ammonia into a molecule of urea.
Nephron
Nephron is the structural and functional unit of the kidney. There are
about a million nephrons
In general, the kidney performs the following vital functions in the
body :
1. Excretion of waste products resulting from protein metabolism.
2. Regulation of acid-base balance by excretion of H+ ions (acidification)
and bicarbonate ions.
3. Regulation of salt-water balance by hormones secreted both intra-and
extra-renally.
4. Formation of renin and erythropoietin and thereby playing a role in the
regulation of blood pressure and erythropoises respectively.
Related Topics in Zoology:
Bio Zoology All Important Topics
- Human Physiology Introduction
- Nutrition
- Carbohydrates Poly hydroxyaldehydes (or) ketones
- Proteins (Polypeptides)
- Lipids
- Vitamins – Functions Of Vitamins
- Deficiency of Vitamin
- Minerals – Water – Role of water
- Balanced diet
- Obesity
- Digestive System
- Dental Caries (Tooth decay)
- Root Canal Treatment
- Peptic ulcer
- Hernia and Types
- Appendicitis (Appendix)
- Gall Stones
- Hepatitis
- Fractures – Types of fractures
- Mechanism of fracture
- Dislocation of joints
- Arthiritis
- Rickets and Osteomalacia – Orthopedics
- Muscles
- Mechanism of muscle contraction
- Types of muscle contraction
- Myasthenia Gravis
- Respiration – Process of pulmonary respiration
- Mechanism of Breathing
- Regulation of Respiration
- Pneumonia Tuberculosis Symptoms Treatment
- Bronchitis – Acute bronchitis, Chronic Bronchitis Causes
- Circulatory System – Functioning of Human heart
- Cardiac Cycle
- Coronary blood vessel and its significance
- Myocardial infarction
- Angina pectoris
- Angiogram – Angioplasty
- Atherosclerosis
- Heart block Echo cardiography Heart Valves
- Rheumatic Heart Disease (RHD), ICCU – (Intensive Coronary Care Unit)
- Blood Pressure
- Heart transplantation
- Pulse rate
- Cardio Pulmonary Resuscitation (CPR)
- Blood – Composition of plasma – Blood cells
- Clotting of Blood or Haemostasis
- Thrombosis
- Nervous system Co-ordination systems
- The Brain – Fore Brain, Midbrain, Hindbrain
- Memory
- Sleep – Types of sleep
- Stroke – Brain haemorrhage
- Alzheimer – Meningitis (Brain fever)
- Conditioned reflex
- Electroencephalography EEG
- Right and Left brain concept
- Spinal cord functioning
- Chemical co-ordination – Functions of Endocrine glands
- Hypothalamus
- Pituitary gland – hormone
- Hormones of Neurohypophysis – vasopressin
- Thyroid gland
- Parathyroid Gland
- Pancreas
- Adrenal gland
- Gonads
- Receptor Organs – Eye
- Photochemistry of Retinal visual Pigments
- Errors of refraction
- Optometry – Retinopathy
- Cataract – Lens Replacement – Glaucoma – Nyctalopia
- Eye Infections and Eye Care
- Ear
- Mechanism of hearing
- Defects of the ear
- Hearing Aid – Noise pollution
- Skin and functions of skin
- Melanin functions
- Effects of solar radiation / UV radiation – Skin grafting
- Dermatitis
- Tongue – Mechanism of Stimulation
- Excretion Ureotelism Nephron
- Mechanism of urine formation
- Renal Failure, Dialysis, Kidney Machines
- Kidney stone – Kidney transplantation
- Diabetes mellitus
- Functioning of male reproductive system
- Functioning of female reproductive system
- Ovulation and fate of the ovum – Menstrual cycle
- Fertilization
- Birth control