Human Physiology & Anatomy — Part 3: 40 MCQs with Explanations

The collecting duct is impermeable to water without ADH (antidiuretic hormone). ADH increases its permeability, allowing water reabsorption and concentrated urine formation.

Parathyroid hormone (PTH) increases blood calcium levels by stimulating bone resorption (osteoclasts), kidney reabsorption of calcium, and activation of vitamin D.

Progesterone, secreted by the corpus luteum (and later placenta), maintains the endometrium, suppresses uterine contractions, and prevents further ovulation during pregnancy.

Salivary amylase (ptyalin), secreted by salivary glands, begins starch digestion in the mouth, breaking it down into maltose.

Adrenaline (epinephrine) and noradrenaline (norepinephrine) are secreted by the adrenal medulla during stress, triggering the 'fight or flight' response.

The nephron is the microscopic structural and functional unit responsible for blood filtration, reabsorption, and secretion to form urine.

O negative blood lacks A, B, and Rh(D) antigens on RBCs, minimizing transfusion reactions in recipients with different blood types.

Vitamin K (phylloquinone/menaquinone) is synthesized by gut bacteria and required for post-translational modification of clotting factors II, VII, IX, X.

The PNS includes cranial nerves, spinal nerves, and ganglia. The CNS consists only of brain and spinal cord.

Thyroxine (T4) and triiodothyronine (T3) increase basal metabolic rate, affect protein synthesis, and regulate development.

The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs. It is the only artery carrying deoxygenated blood.

The liver converts toxic ammonia (from amino acid deamination) into urea via the ornithine cycle for safe excretion by kidneys.

Fertilization usually occurs in the ampulla region of the uterine tube (fallopian tube), after which the zygote travels to uterus for implantation.

Adrenaline (epinephrine) from adrenal medulla increases heart rate, blood pressure, and blood glucose during acute stress.

Gas exchange is a respiratory function. The skeleton provides support, protects organs, enables movement, stores minerals, and houses red bone marrow for hematopoiesis.

The appendix is a remnant of a larger cecum used for cellulose digestion in herbivorous ancestors; it has minimal function in humans (possible lymphoid tissue role).

Fossil evidence shows progression: Australopithecus (4-2 mya) → Homo habilis (2.4-1.4 mya) → Homo erectus (1.9 mya-140 kya) → Homo sapiens (300 kya-present).

Pulmonary veins carry oxygenated blood from lungs to left atrium. They are the only veins carrying oxygenated blood.

The sarcomere, functional unit of muscle contraction, extends from one Z-line to the next Z-line and contains actin and myosin filaments.

Skin synthesizes vitamin D₃ precursor (7-dehydrocholesterol) upon UV exposure but does not produce hormones; endocrine glands produce hormones.

PTH increases blood Ca²⁺ by stimulating osteoclasts (bone resorption), renal Ca²⁺ reabsorption, and calcitriol (active vitamin D) production.

The iris contains radial and circular muscles that adjust pupil size to regulate light entering the eye (constricts in bright light, dilates in dim light).

Urea synthesis occurs in the liver. Kidneys filter blood, regulate blood pressure (via renin), produce erythropoietin, and maintain electrolyte/water balance.

Internal respiration: O₂ diffuses from systemic capillaries to tissues; CO₂ diffuses from tissues to blood. External respiration occurs in lungs.

The hypothalamus maintains homeostasis including body temperature (via sweating/shivering), hunger, thirst, sleep, and hormone release from pituitary.

Thrombin (serine protease) cleaves soluble fibrinogen into insoluble fibrin monomers that polymerize to form the clot mesh.

The medulla regulates essential involuntary functions: respiration, heart rate, blood pressure, and reflexes (vomiting, coughing, swallowing).

Lymphatic vessels return interstitial fluid to blood, lacteals absorb dietary fats, and lymph nodes filter pathogens and house lymphocytes.

Under oxygen debt, pyruvate is reduced to lactate by lactate dehydrogenase, regenerating NAD⁺ for continued glycolysis.

Vitamin D deficiency impairs calcium absorption, causing rickets in children (soft, deformed bones) and osteomalacia in adults.

Countercurrent multiplication: descending limb permeable to water, ascending limb actively transports NaCl out, establishing hypertonic medulla for urine concentration.

The patella (kneecap) is a sesamoid bone embedded in the quadriceps tendon, protecting the knee joint and improving leverage.

ADH (vasopressin) increases permeability of collecting duct to water by inserting aquaporins, concentrating urine during dehydration.

Hypothalamus connects to posterior pituitary via neural tract (releasing oxytocin/ADH) and to anterior pituitary via hypophyseal portal system (releasing/inhibiting hormones).

The SA node in right atrium wall generates electrical impulses (60-100 bpm) that initiate heartbeat and set rhythm.

The corpus luteum (formed from ruptured follicle after ovulation) secretes progesterone and estrogen to maintain pregnancy.

LH surge from anterior pituitary triggers ovulation approximately 24-36 hours after surge onset.

AB positive is universal recipient for RBC transfusion (has no anti-A, anti-B, or anti-Rh antibodies). O negative is universal donor.

Venous valves (especially in limbs) prevent backflow, ensuring blood returns to heart against gravity.

Acetylcholine released from motor neurons binds nicotinic receptors on skeletal muscle, triggering depolarization and contraction.

The structure which has been formed or modified from gill pouches in humans is Eustachian tube .

Pulmonary vein is the correct answer to “All of the following veins carry deoxygenated blood except”. Items of this type are drawn from the Human Physiology & Anatomy — Part 3 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

The major constituent of blood plasma is Water .

The human naked eye can differentiate between two points which are 1.0 mm apart.

In human female, fertilization commonly occurs at Proximal part of oviduct .

Which of the following hormone is polypeptide in nature ADH .

Deoxygenated blood first enters in Sinus venosus part in fishes.

Oxygen accounts for 65% percent of totals human body mass.

The branch of biology which deals with the study of social behavior and communal life of human beings living in any environment is called Social biology .

Homo sepions is a scientific word for human beings.

pulmonary trunk is the correct answer to “From right ventricle blood is pushed into”. Items of this type are drawn from the Human Physiology & Anatomy — Part 3 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

In human body 99% of total mass is formed of 6 Bio-elements .

Oxygen accounts for 65% % of totals human body mass.

Blood is carried towards the heart by Veins .

Social biology is the correct answer to “The branch of biology which deals with the study of social behavior and communal life of human beings living in any environment is called”. Items of this type are drawn from the Human Physiology & Anatomy — Part 3 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

The average internal temperature of human body is 37 oC .

Human blood is an example of Tissues .

It regulates the heart beat is the correct answer to “What is the function of heart pacemaker”. Items of this type are drawn from the Human Physiology & Anatomy — Part 3 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

Throats is the correct answer to “The disease Diphtheria affect the ———— in the human body.”. Items of this type are drawn from the Human Physiology & Anatomy — Part 3 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

D.Vitamin K is the correct answer to “Which Vitamin help blood clotting”. Items of this type are drawn from the Human Physiology & Anatomy — Part 3 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

C.Vitamin C is the correct answer to “Which Vitamins is not stored in Human Body”. Items of this type are drawn from the Human Physiology & Anatomy — Part 3 syllabus of Pakistani competitive exams, where the fact is tested verbatim.