Goitre is a swelling of the neck due to enlargement of the thyroid gland. This may be due to a lack of dietary iodine, which occurs due to decreases thyroid function, which is necessary for the production of thyroxine hormone.

This was the casue of endemic goitre formerly common in regions, where the people lacked in their diet iodine.

Diastema is the gap that separates the big teeth from the grinding teeth in herbivores. It creates a space in which food can be held ready for the grinding action of the teeth. This space is filled with large canine teeth in carnivores.

Study of amphibians and reptiles is called Herpetology.

Study of aves is called Ornithology.

Study of fishes is called Ichthyology.

Ligaments join a bone with another bone in movable/ synovial joints. Torn ligaments make a movement at joints very painful and restricted. It heals only after prolonged movement restriction.

Prolactin or luteotrophic hormone or luteotropin is a hormone, synthesised and stored in the anterior pituitary gland, that stimulates milk production after childbirth and also stimulates the production of progesterone by the corpus luteum in the ovary.

Bone marrow is of two types; red and yellow. The yellow marrow is found especially in the medullary cavity of long bones, while red is in spongy bones.

At its bottom, the trachea (another name for the windpipe) branches into two tubes called bronchi, which lead into the lungs.

The larynx is the voice box. It is connected to the windpipe. The oesophagus, like the windpipe, is a tube that runs through the neck. The lungs are the ballon like structure in the chest.

Pepsin is released from peptic cells of the gastric gland on the stomach wall and it can digest milk protein casein.

Chymotrypsin is released from the intestine and digest proteins. Ptyalin is released from salivary glands and acts on starch.

Achondroplasia is a defect in the formation of cartilage at the epiphyses of long bones producing a form of dwarfism.