Zoology: Human Physiology and Diseases

What to remember

• Each organ system has a job: digestion breaks food, respiration supplies oxygen, circulation transports, excretion removes wastes, the nervous and endocrine systems control the body, and the reproductive system continues the species.
• The heart has four chambers; blood has plasma, red cells, white cells and platelets. Haemoglobin carries oxygen.
• Diseases are caused by germs (bacteria, viruses, protozoa, fungi), by lack of nutrients (deficiency) or by genes. Vaccines prevent many infectious diseases.

Digestive system

Digestion changes large food molecules into small soluble ones that blood can absorb.

Path of food: mouth, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus.

• Mouth: teeth chew food. Saliva has the enzyme salivary amylase (ptyalin), which starts breaking starch into sugar.
• Stomach: gastric glands release hydrochloric acid, pepsin and mucus. The acid kills germs and makes a medium for pepsin, which digests proteins. Mucus protects the wall.
• Small intestine: the longest part. Digestion is completed here. Bile from the liver breaks fat into small droplets (emulsification). The pancreas gives pancreatic juice with amylase, trypsin and lipase. The inner wall has finger-like villi, which increase the area for absorption.
• Large intestine: absorbs water and forms faeces.
• Liver: the largest gland in the body. It makes bile (stored in the gall bladder), stores glycogen and removes toxins.

Nutrition basics: carbohydrates and fats give energy; proteins build the body; vitamins and minerals protect it. Water and roughage (fibre) are also needed.

Respiratory system

Path of air: nostrils, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles and alveoli. The alveoli are tiny air sacs with thin walls and many capillaries, where oxygen enters blood and carbon dioxide leaves.

• Inhalation: the diaphragm moves down and the ribs move up and out. The chest cavity expands and air rushes in.
• Exhalation: the diaphragm moves up and the ribs go down. Air is pushed out.
• Haemoglobin in red blood cells carries oxygen. Most carbon dioxide travels as bicarbonate in plasma.
• Breathing is a physical process. Cellular respiration is a chemical process that releases energy in cells.
• The voice box (larynx) holds the vocal cords.

Circulatory system

Blood is a fluid connective tissue.

Blood groups (A, B, AB, O) were discovered by Karl Landsteiner. Group O is the universal donor in red cell transfusion; group AB is the universal recipient. The Rh factor is another protein on red cells.

Heart: a muscular organ with four chambers: two upper atria and two lower ventricles. The right side carries deoxygenated blood and the left side carries oxygenated blood. The left ventricle has the thickest wall. A normal adult heart rate at rest is about 72 beats per minute.

Blood flow: body, right atrium, right ventricle, lungs (via pulmonary artery), left atrium, left ventricle, body (via aorta). Humans have double circulation.

• Arteries: carry blood away from the heart; thick walls. The pulmonary artery is the only artery carrying deoxygenated blood.
• Veins: carry blood to the heart; have valves. The pulmonary vein carries oxygenated blood.
• Capillaries: thin vessels where exchange takes place.
• Lymph is a clear fluid which helps immunity and returns fluid to blood.

Excretory system

Excretion is the removal of metabolic wastes. The main organs are a pair of kidneys, two ureters, the urinary bladder and the urethra. The nephron is the functional unit of the kidney. It filters blood, reabsorbs useful materials and forms urine. Urea is the main nitrogen waste in humans. When the kidneys fail, dialysis (artificial filtering) can do their work, or a kidney transplant can replace a diseased kidney.

Other excretory organs: the lungs (carbon dioxide), the skin (sweat) and the liver (makes urea).

Nervous and endocrine systems

Neuron is the unit of the nervous system. It has a cell body, dendrites and an axon. A synapse is the gap between two neurons.

• Central nervous system: brain and spinal cord.
• Brain parts: the cerebrum (thinking, memory), cerebellum (balance and posture), medulla (involuntary actions such as heartbeat and breathing).
• Reflex action is a quick, automatic response, such as pulling the hand from a hot object. It follows the reflex arc and is controlled by the spinal cord.
• Sense organs: eye, ear, nose, tongue and skin.

Endocrine glands release hormones directly into blood.

Low insulin causes diabetes. Lack of iodine causes goitre. The pituitary controls other glands, but the hypothalamus controls the pituitary.

Reproductive system and heredity

Male organs: testes, sperm ducts and penis. Female organs: ovaries, fallopian tubes, uterus and vagina. Fertilisation is the union of sperm and egg, usually in the fallopian tube. The embryo implants in the uterus, and the placenta gives food and oxygen to it. Humans reproduce sexually and are viviparous (give birth to young).

Heredity basics: Gregor Mendel, the "Father of Genetics", worked with pea plants. A gene is a unit of heredity on a chromosome. Humans have 23 pairs (46) of chromosomes. The sex chromosomes are XX in females and XY in males. The father's chromosome decides the sex of the child. DNA carries genetic information.

Common diseases

Prevention: Vaccines build immunity. Edward Jenner developed the first vaccine, for smallpox. Smallpox is eradicated. Clean water, hygiene, mosquito control and a balanced diet also help. Antibiotics act on bacteria, not on viruses.

Colour blindness and haemophilia are genetic disorders that are linked to the X chromosome. Diabetes is a metabolic disorder.

Immunity, nutrition and skeleton

Immunity is the body's power to fight disease. The skin and mucus are the first barrier. White blood cells make antibodies against antigens. A vaccine has a weak or dead germ that trains the body without causing the disease. Breast milk (the first yellowish milk, colostrum) passes natural antibodies to a newborn baby.

Balanced diet: includes carbohydrates, proteins, fats, vitamins, minerals, water and fibre. Protein lack causes kwashiorkor and marasmus in children. Vitamins A, D, E and K dissolve in fat; vitamins B and C dissolve in water. Vitamin K helps blood to clot. Vitamin B12 lack leads to a type of anaemia. Calcium and phosphorus build bones and teeth.

Skeleton and muscles: An adult human has 206 bones. The longest bone is the femur (thigh bone); the smallest is the stapes in the ear. Joints such as the ball and socket joint (shoulder, hip) allow movement in many directions, while hinge joints (knee, elbow) allow movement in one direction. Muscles are of three types: skeletal (voluntary), smooth (involuntary, in the gut) and cardiac (heart muscle).

Sense organs in brief: The eye has a transparent cornea, an iris that controls the size of the pupil, a lens that focuses light and a retina that holds rods (dim light) and cones (colour). The ear has an outer, middle and inner part; the inner ear also helps in balance. The tongue senses sweet, sour, salty, bitter and umami. Skin senses touch, pain and temperature.

Exam traps

• Arteries carry blood away from the heart; veins carry blood to the heart. The pulmonary artery carries deoxygenated blood.
• Bile is made in the liver and stored in the gall bladder; it has no enzyme.
• Alveoli are in the lungs; villi are in the small intestine; nephrons are in the kidney.
• Insulin lowers blood sugar; adrenaline prepares for emergency.
• Malaria is caused by a protozoan, not a virus or bacterium.
• Scurvy is lack of vitamin C; rickets is lack of vitamin D.
• The cerebellum controls balance; the medulla controls involuntary actions.
• The father's chromosome decides the sex of the child.

One-liners

• 1. Salivary amylase starts starch digestion in the mouth.
• 2. Pepsin acts on proteins in the stomach.
• 3. Villi increase the area for absorption.
• 4. The liver is the largest gland.
• 5. Alveoli are the sites of gas exchange.
• 6. Haemoglobin carries oxygen.
• 7. The heart has four chambers.
• 8. The nephron is the functional unit of the kidney.
• 9. The neuron is the structural unit of the nervous system.
• 10. The thyroid needs iodine to make thyroxine.
• 11. Humans have 23 pairs of chromosomes.
• 12. Edward Jenner developed the smallpox vaccine.

Practice questions

1. The enzyme in saliva that starts the digestion of starch is

   1. Pepsin
   2. Salivary amylase
   3. Trypsin
   4. Lipase
   Answer

   B. Salivary amylase

   Salivary amylase (ptyalin) changes starch to sugar.

2. Proteins are digested in the stomach by

   1. Amylase
   2. Bile
   3. Lipase
   4. Pepsin
   Answer

   D. Pepsin

   Pepsin works in the acid medium of the stomach.

3. Bile juice helps in the

   1. Digestion of proteins
   2. Emulsification of fats
   3. Absorption of water
   4. Digestion of starch
   Answer

   B. Emulsification of fats

   Bile breaks fat into small droplets; it has no enzymes.

4. Bile is stored in the

   1. Stomach
   2. Spleen
   3. Pancreas
   4. Gall bladder
   Answer

   D. Gall bladder

   The liver makes bile and the gall bladder stores it.

5. The largest gland in the human body is the

   1. Pancreas
   2. Thyroid
   3. Liver
   4. Pituitary
   Answer

   C. Liver

   The liver is the largest gland.

6. Finger-like villi in the small intestine increase the

   1. Production of bile
   2. Speed of peristalsis
   3. Acidity of food
   4. Surface area for absorption
   Answer

   D. Surface area for absorption

   More area means more absorption of digested food.

7. Most water from undigested food is absorbed in the

   1. Stomach
   2. Oesophagus
   3. Large intestine
   4. Gall bladder
   Answer

   C. Large intestine

   The large intestine forms faeces after absorbing water.

8. Gas exchange in the lungs takes place in the

   1. Larynx
   2. Alveoli
   3. Bronchi
   4. Trachea
   Answer

   B. Alveoli

   Alveoli are thin-walled sacs with capillaries.

9. During inhalation, the diaphragm

   1. Moves up
   2. Becomes the lungs
   3. Does not move
   4. Moves down
   Answer

   D. Moves down

   The chest cavity expands as the diaphragm moves down.

10. The voice box that holds the vocal cords is the

    1. Pharynx
    2. Larynx
    3. Oesophagus
    4. Trachea
    Answer

    B. Larynx

    Larynx is at the top of the windpipe.

11. Haemoglobin is found in

    1. Red blood cells
    2. White blood cells
    3. Platelets
    4. Plasma only
    Answer

    A. Red blood cells

    Haemoglobin carries oxygen in RBCs.

12. Blood clotting is helped by

    1. Red blood cells
    2. Haemoglobin
    3. Lymph only
    4. Platelets
    Answer

    D. Platelets

    Platelets help to stop bleeding.

13. Which blood group is called the universal recipient for red cells?

    1. A
    2. O
    3. AB
    4. B
    Answer

    C. AB

    Group AB has no anti-A or anti-B antibodies.

14. Blood groups were discovered by

    1. Gregor Mendel
    2. Karl Landsteiner
    3. Edward Jenner
    4. William Harvey
    Answer

    B. Karl Landsteiner

    Landsteiner found the ABO groups.

15. The thickest-walled chamber of the human heart is the

    1. Right atrium
    2. Left atrium
    3. Left ventricle
    4. Right ventricle
    Answer

    C. Left ventricle

    It pumps blood to the whole body.

16. The only artery that carries deoxygenated blood is the

    1. Pulmonary artery
    2. Aorta
    3. Coronary artery
    4. Renal artery
    Answer

    A. Pulmonary artery

    It takes blood from the heart to the lungs.

17. Valves are found in

    1. Alveoli
    2. Arteries
    3. Capillaries
    4. Veins
    Answer

    D. Veins

    Valves keep blood from flowing backward in veins.

18. The functional unit of the kidney is the

    1. Alveolus
    2. Nephron
    3. Villus
    4. Neuron
    Answer

    B. Nephron

    The nephron filters blood and forms urine.

19. The main nitrogenous waste in humans is

    1. Glucose
    2. Uric acid in birds
    3. Urea
    4. Ammonia
    Answer

    C. Urea

    Urea is made in the liver and removed by the kidneys.

20. The part of the brain that controls balance and posture is the

    1. Cerebellum
    2. Medulla
    3. Cerebrum
    4. Spinal cord
    Answer

    A. Cerebellum

    The cerebellum coordinates balance.

21. Involuntary actions such as heartbeat and breathing are controlled by the

    1. Retina
    2. Cerebrum
    3. Medulla
    4. Cerebellum
    Answer

    C. Medulla

    Medulla oblongata is in the brain stem.

22. A quick, automatic response to a stimulus is a

    1. Voluntary action
    2. Reflex action
    3. Hormonal action
    4. Learned action
    Answer

    B. Reflex action

    It is controlled by the spinal cord.

23. The hormone that lowers blood sugar is

    1. Thyroxine
    2. Testosterone
    3. Adrenaline
    4. Insulin
    Answer

    D. Insulin

    Insulin is made in the pancreas.

24. Goitre is caused by lack of

    1. Iodine
    2. Iron
    3. Vitamin C
    4. Calcium
    Answer

    A. Iodine

    Iodine is needed for thyroxine.

25. The gland called the 'master gland' is the

    1. Pancreas
    2. Adrenal
    3. Pituitary
    4. Thyroid
    Answer

    C. Pituitary

    It controls many other glands.

26. The hormone that prepares the body for fight or flight is

    1. Oestrogen
    2. Thyroxine
    3. Insulin
    4. Adrenaline
    Answer

    D. Adrenaline

    Adrenaline is released by the adrenal glands.

27. Humans have how many pairs of chromosomes?

    1. 46
    2. 23
    3. 22
    4. 48
    Answer

    B. 23

    There are 23 pairs, or 46 chromosomes.

28. The sex of a human child is decided by the chromosome of the

    1. Mother
    2. Both equally in all cases
    3. Grandmother
    4. Father
    Answer

    D. Father

    Males produce X or Y sperm; females give only X.

29. Malaria is caused by a

    1. Virus
    2. Protozoan
    3. Fungus
    4. Bacterium
    Answer

    B. Protozoan

    The parasite is Plasmodium.

30. Scurvy is a deficiency of

    1. Vitamin C
    2. Vitamin B1
    3. Vitamin A
    4. Vitamin D
    Answer

    A. Vitamin C

    Vitamin C prevents scurvy.

31. Rickets in children is caused by lack of

    1. Iodine
    2. Vitamin C
    3. Vitamin D
    4. Vitamin K
    Answer

    C. Vitamin D

    Vitamin D helps the body use calcium.

32. Night blindness is due to a deficiency of

    1. Vitamin B1
    2. Vitamin C
    3. Vitamin E
    4. Vitamin A
    Answer

    D. Vitamin A

    Vitamin A is needed for the retina.

33. The first vaccine, for smallpox, was developed by

    1. Edward Jenner
    2. Louis Pasteur
    3. Robert Koch
    4. Alexander Fleming
    Answer

    A. Edward Jenner

    Jenner used cowpox to protect against smallpox.

34. Antibiotics are effective against

    1. All germs equally
    2. Genetic disorders
    3. Bacteria
    4. Viruses
    Answer

    C. Bacteria

    They do not act on viruses.

35. Consider the statements about the circulatory system. 1. Arteries carry blood away from the heart. 2. The pulmonary vein carries deoxygenated blood.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    The pulmonary vein carries oxygenated blood.

36. Consider the statements about the digestive system. 1. Bile contains digestive enzymes. 2. The liver produces bile.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Bile has no enzymes; the liver produces it.

37. Consider the statements about the human heart. 1. It has four chambers. 2. The right side carries oxygenated blood in a normal adult.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    The right side carries deoxygenated blood.

38. Consider the statements about endocrine glands. 1. Endocrine glands release hormones directly into the blood. 2. The thyroid gland produces insulin.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Insulin comes from the pancreas.

39. Consider the statements about diseases. 1. Dengue is spread by mosquitoes. 2. Tuberculosis is a viral disease.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Tuberculosis is bacterial.

40. Consider the statements about the nervous system. 1. The neuron is the structural unit of the nervous system. 2. A synapse is the gap between two neurons.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are correct.

41. Consider the statements about heredity. 1. Gregor Mendel worked on pea plants. 2. XX are sex chromosomes of human males.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Males are XY; females are XX.

42. Consider the statements about respiration. 1. Alveoli have thin walls and many capillaries. 2. Breathing and cellular respiration mean the same thing.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Breathing is physical; cellular respiration is chemical.

43. Consider the statements about genetic disorders. 1. Haemophilia is linked to the X chromosome. 2. Colour blindness is caused by a virus.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Colour blindness is a genetic disorder.

44. Match the organ (left) with its function (right). P. Liver Q. Kidney R. Lungs S. Pancreas

    1. P-forms urine, Q-makes bile, R-gas exchange, S-makes insulin
    2. P-makes bile, Q-gas exchange, R-forms urine, S-makes insulin
    3. P-makes bile, Q-forms urine, R-makes insulin, S-gas exchange
    4. P-makes bile, Q-forms urine, R-gas exchange, S-makes insulin
    Answer

    D. P-makes bile, Q-forms urine, R-gas exchange, S-makes insulin

    These are the main functions of the organs.

45. Match the disease (left) with its cause (right). P. Beriberi Q. Anaemia R. Ringworm S. Polio

    1. P-fungus, Q-lack of iron, R-lack of vitamin B1, S-virus
    2. P-lack of vitamin B1, Q-lack of iron, R-fungus, S-virus
    3. P-lack of vitamin B1, Q-lack of iron, R-virus, S-fungus
    4. P-lack of iron, Q-lack of vitamin B1, R-fungus, S-virus
    Answer

    B. P-lack of vitamin B1, Q-lack of iron, R-fungus, S-virus

    Option A gives the correct cause for each disease.