Tag: human brain and sense organs

The large round lens of the frog gives the animal a large field of view. The frog is naturally nearsighted (myopic) to -6 diopters giving it a focus of approximately 6 inches. Frogs and toads can change their focus by moving the lens out towards the cornea. 

Frogs use their regular set of eyelids to keep their eyes moist and clean. They have a bottom lid that stays still and an upper lid that blinks. Frogs also have a third eyelid that serves a different purpose. This one, called as the nictitating membrane, is a semitransparent lid that covers the eye completely, helping the frog see underwater and hide from predators. 

The tapetum lucidum is a layer of tissue in the eye of many vertebrates. Lying immediately behind the retina it reflects visible light back through the retina, increasing the light available to the photoreceptors. The tapetum lucidum contributes to the superior night vision of some animals. Many of these animals are nocturnal, especially carnivores that hunt their prey at night, while others are deep sea animals. Choroidal guanine tapetum is seen in Elasmobranchii (skates, rays, and sharks) and chimaeras. The tapetum is a palisade of cells containing stacks of flat hexagonal crystals of guanine.

The conjunctiva is the thin film composed of non-keratinized stratified columnar epithelium and goblet cells that line the inside of the eyelids and covers the white of the eye called as the sclera. The conjunctiva lubricates the produces mucus and tears in small amounts to lubricate the eye and also prevents the entry of microbes into the eye.
Therefore, the correct answer is option C.

The person wearing spectacles with concave lenses for correcting vision suffers from myopia (near sightedness). In such a person, the image of distant object will be formed in front of retina, if he is not using the glasses.

The structures of the eye that deflect light is called refractive medium. Light is actually refracted through four media in the eye. The first is the cornea (the clear layer on the outside of the eye), then the aqueous humour (liquid), then the lens (which can change shape slightly to allow objects near and far to focus), and then there is the vitreous humour (liquid filling most of the inside of the eye) all of which light needs to pass through before it reaches the retina. Light enters the eye through the pupil, and the iris regulates the amount of light by controlling the size of the pupil. Since, pupil only contacts and dilates, therefore, it is the one not a refractive medium of the eye. So, the correct answer is option D.

The skin is one of the largest organs in the body in surface area and weight. The skin consists of two layers: epidermis and dermis. Beneath the dermis lies the subcutaneous fatty tissue. The skin has three main functions: protection, regulation and sensation.

Melanoma, also known as malignant melanoma is a type of cancer that develops from the pigment-containing cells known as melanocytes. Melanomas typically occur in the skin, but may rarely occur in the mouth, intestines, or eye. Sometimes they develop from changes in wart or mole such as an increase in size, irregular edges, change in colour, itchiness, or skin breakdown.

• The odoriferous properties of human feces are due to the compounds Indoles, Skatole, and Mercaptans.
  
• The yellow color of the feces is due to Stercobilin which is derived by breaking down Bile salts.
  
• So, the correct option is 'Stercobilin'.