The nervous system, including neurons and sense organs, originates from ectoderm in vertebrates. 

Mitral valve is also known as bicuspid valve. SA node is located in the right atrial wall below the opening of the superior vena cava and called pace maker of heart. Lymphocyte is a sub-category of leucocyte, i.e. white blood corpuscles (WBC). Plasma is the matrix of blood (i.e. blood - corpuscles after clotting (i.e. blood - corpuscles + fibrinogen). 

The main nitrogenous waste of Hydra is ammonia. Hydra has no organ of excretion, therefore, excretion of waste nitrogenous matter occurs directly by diffusion through cell membrane. 

Anti-sterility vitamin is vitamin E. It is required for the normal reproductive function in rats, hence, called anti-sterility vitamin. In absence of vitamin E, the germinal epithelium of the testes of rat is destoryed. In the female rat, ovulation and fertilization take place, but there is death and resorption of the foetus. 

The autonomic nervous system (ANS) regulates the functions of our internal organs (the viscera) such as the heart, stomach and intestines. The ANS is part of the peripheral nervous system and it also controls some of the muscles within the body.

In a mammalian neuron, action potential is produced by Na⁺ ions.

When the intensity of light is low during night the light is detected by rods. In eyes rod cells are used for peripheral vision (scotopic vision). 

Each cocoon of silk worm (Bombyx mori) has about 1000 meter of silk thread. During its short life the female moth lays about three to five hundred whitish eggs. A minute caterpillar larva hatches out from each egg in about 10 days. The larva starts pouring out its sticky saliva through a minute aperture called spinneret located upon the lower lip of its mouth. As it comes out in air the lpuid saliva immediately solidify into a fine silk thread. 

Endometrium is a mucus membrane linning of mammalian uterus that disintegrates and regenerates during menstrual cycle. Menstruation is the periodic shedding of the endometrium of the uterus with bleeding.

Brain is not involved in the elicitation of the immune system. Lymphoids organs (i.e. organs where maturation and proliferation of lymphocytes occurs) are involved in the elicitation of the immune system. Thymus, bursa of fabricus of birds and bone marrow are primary lymphoid organs whereas lymph nodes, spleen and mucosa associated lymphoid tissues such as tonsils, Peyer's patches, etc. are scondary lymphoid organs. 

Dental formula of man is 2123/2123. The formula 2.1.2.3 for upper and lower teeth indicates 2 incisors, 1 canine, 2 premolars, and 3 molars on one side of the both upper and lower arches.

Pancreatic juice secretion is regulated by the hormones secretin and cholecystokinin. It is produced by the walls of the duodenum upon detection of acid food, proteins, fats, and vitamins.

Gamma amino butyric acid (Gaba) and glycine are inhibitory transmitters. An inhibitory transmitter is  released by an inhibitory neuron. It can inhibit impulse at a synapse.

Single contractile vacuole is found in fresh water Amoeba. It appears like a bubble of clear, watery fluid, enclosed within a decicate and elastic condensation membrane resembling plasmalemma. its function is osmoregulation, i.e. excess amount of water collected in it an discharged out by it. The water collected in contractile vacuole contain trace of ammonia.

The septal nephridia and pharngeal nephridia dishcarge thier waste products into the lumen of the alimentary canal and not outside. These are knwon as enteronephric types of nephridia. In Pheretima three types of nephridia are present

1.        Septal nephridia
2.        Pharyangeal nephridia
3.        Integumentary nephridia. 

 Adrenal gland secretes Fight, fright and flight hormone. Due to an increased quantity of blood is pumped faster to heart muscles and brain; it is well oxygenated and rich in nutrients. These preparations are valuable for the body in providing a rapid physiologic response to emergencies sucha as shock, fear, and danger. 

Polydactyly means having more than five digits in hand or feet. It is an abnormal hereditary trait which occurs due to dominant defective autosomal genes. 

Hashimoto's thyroiditis or chronic lymphocytic thyroiditis is an autoimmune disease in which the thyroid gland is attacked by a variety of cell- and antibody-mediated immune processes, causing primary hypothyroidism.

The crypts of Lieberkuhn are simple, tubular structures which occur through out the small intestine and involved in th secretion of intestinal juice or succus entericus. 

Thoracic cage of man is formed by ribs. sterum and thoracic vertebrae. Ribs are found articulating with the thoracic vertebrae. 

In vertebrates skeleton muscles are mesodermal in origin. 

Pacinian corpuscles are  tactile receptors (tangoreceptors) occur in deeper layer of skin dermis of palms, sole, fingers, external genitals, nipples, arms , neck, joints ect. These are oval, spherical or irregularly coiled and very characteristic in structure. All tactile receptors are involved in deterction of vibration, although different receptors detect different receptors detect different frequencies of vibration. (30 - 800 cycles per second by pacinian corpuscles. 

Life cycle of Plasmodium is completed in two hosts. Man is considered to be the primary host in which schizogony occurs in liver and blood, and female Anopheles mosquito is the secondary or intermediate host in which gametogony and sporogony takes place.

In a population where competition between individual is severe then the distribution is said to be random. Here, the position of one individual is unrelated to the position of its neighbours. 

The proximal convoluted tube absorbs by active transport all the glucose and amino acids that are part of the original filtrate from the glomeruli. Also sodium, water, phosphate.