General Science GK Questions with Answers – Page 76

After ovulation the ruptured Graafian follicle turns into the yellow body called the corpus luteum, which secretes large amounts of progesterone to thicken and maintain the endometrium for implantation.

It is secreted by the trophoblast of the implanted blastocyst and then by the placenta, appears in the blood and urine within a few weeks of conception, and is unique to pregnancy, so test kits use antibodies against it.

The acrosome is a cap-like structure over the sperm nucleus filled with enzymes that digest the layers around the egg so that one sperm can fuse with it.

Sertoli cells line the seminiferous tubules and provide nutrition and support to the germ cells as they divide and change into sperms, which is why they are called nurse cells; they are controlled mainly by follicle stimulating hormone.

The correct answer is B, the Leydig or interstitial cells, which lie in the spaces between the seminiferous tubules of the testis and secrete androgens, chiefly testosterone, under the influence of luteinising hormone from the anterior pituitary.

The ovum released at ovulation is picked up by the fimbriae of the infundibulum and meets the sperm in the ampulla, the wide middle part of the tube, where fusion takes place to form the zygote.

Vitamin D, which the skin makes in sunlight and which is also present in milk, eggs and fish liver oil, is needed for the absorption of calcium and phosphorus from food.

Cardiac muscle shows the cross stripes of skeletal muscle under the microscope, but it is not under the control of the will and it beats rhythmically on its own, driven by the pacemaker of the heart; its cells are branched and joined end to end by intercalated discs, which let…

In the sliding filament theory of contraction, a nerve impulse causes calcium to be released from the sarcoplasmic reticulum; the calcium exposes binding sites on the thin actin filaments, the heads of the thick myosin filaments attach to them and swivel, using energy from ATP, and the actin is pulled…

A tendon is a cord of white fibrous connective tissue, with very little elasticity, that transmits the pull of a contracting muscle to the bone it moves; the Achilles tendon at the heel is the best known example.

The rounded head of the humerus sits in the socket of the shoulder blade and the head of the femur sits in the socket of the hip bone, which lets the limb move forwards, backwards, sideways and in rotation; these are synovial joints with a fluid-filled cavity.

All of them are attached behind to the thoracic vertebrae. In front, the first seven pairs join the sternum directly and are called true or vertebrosternal ribs; the next three pairs join the seventh rib through cartilage and are called false or vertebrochondral ribs; and the last two pairs have…

The adult column is counted as seven cervical vertebrae in the neck, twelve thoracic vertebrae bearing the ribs, five lumbar vertebrae in the lower back, one sacrum and one coccyx, giving twenty-six bones in all.

It is the innermost of the three ear ossicles of the middle ear and is shaped like a stirrup; it passes vibrations from the incus to the oval window of the inner ear and is the smallest bone of the body.

The adult skeleton has eighty bones in the axial part, that is the skull with the ear ossicles and hyoid, the vertebral column, the ribs and the sternum, and one hundred and twenty-six in the appendicular part, that is the limbs with the pectoral and pelvic girdles, making two hundred…

An adult set of thirty-two permanent teeth has eight incisors for cutting, four canines for tearing, eight premolars and twelve molars for grinding, so there is one canine on each side of each jaw.

It is a thin, strap-like muscle that runs across the front of the thigh from the hip bone to the inner side of the knee, and because it crosses two joints it is the longest muscle of the human body; it helps in bending the hip and the knee and…

Inertia depends only on mass, and a cricket ball is the heaviest of the four. Inertia is the tendency of a body to stay at rest or keep moving uniformly in a straight line unless a force acts on it; this is Newton's first law.

Infectious jaundice, caused mainly by the hepatitis A and hepatitis E viruses, spreads through water and food contaminated with faeces.

In ferric oxide both iron atoms are in the same +3 oxidation state. In Fe₂O₃ three oxide ions carry a total charge of −6, shared equally by two iron atoms, so each iron is +3.