Human Digestive System

In herbivores, the caecum is the primary site for the microbial fermentation and digestion of cellulose. Humans have a vestigial caecum, but the organ remains associated with this function in biological context.

Rabbits are hindgut fermenters that rely on a large, specialized caecum to house symbiotic bacteria for the breakdown of cellulose. Humans, cats, and frogs do not utilize the caecum for this purpose.

The large intestine, specifically the colon, is the primary site for the reabsorption of water and electrolytes from the remaining chyle. This process helps in the formation of solid faeces.

As in other herbivorous mammals, the caecum in rabbits serves as a fermentation chamber where symbiotic microorganisms break down cellulose into absorbable nutrients.

The human caecum houses a population of symbiotic microorganisms that contribute to gut health. While the human caecum is reduced compared to herbivores, it still serves as a reservoir for these bacteria.

The ileocaecal valve is a sphincter muscle located at the junction of the small intestine (ileum) and the large intestine (caecum). It prevents the backflow of faecal material into the small intestine.

The vermiform appendix is a small, blind-ended tube that is attached to the caecum, which is the initial part of the large intestine.

Argentaffin cells (also known as enterochromaffin cells) are specialized endocrine cells found throughout the gastrointestinal tract, including the stomach, small intestine, and large intestine. Given the options, the large intestine is a correct site, though they are present in other areas too.

Statement 1 accurately describes the anatomical location and appearance of the vermiform appendix. Statement 2 is also correct, as the appendix is considered a vestigial organ with no significant digestive function in humans.

Human Saliva -6.8
Human Blood -7.4
Gastric Juice-1.8
Urine-6

$HCl$ is present in free state in volcanic emissions and it is also available in gastric juices of mammals and helps in digestion process.
Hence option C is correct.

Velamen is a spongy, multiple epidermis that covers the roots of some epiphytic or semi-epiphytic plants, such as orchid and Clivia species. The velamen of an orchid is the white or gray covering of aerial roots when dry, and usually more green when wet as a result of the appearance of underlying photosynthetic structures. It is many cell layers thick and capable of absorbing atmospheric moisture and nutrients. Often, the roots of orchids are associated with symbiotic fungi or bacteria, the latter may fix nutrients from the air. This functionality allows the orchid to exist in locations that provide a reproductive or vegetative advantage such as improved exposure or reduced competition from other plant species. The velamen also serves a mechanical function, protecting the vascular tissues in the root cortex, shielding the root from transpirational water loss and in many cases, adhering the plant to the substrate. So, velamen tissues are associated with absorption of moisture and not with nutrition, assimilation and haustorial function.
Thus, the correct answer is option C.

Nutrition is the science that interprets the interaction of nutrients and other substances in food in relation to maintenance, growth, reproduction, health and disease of an organism. It includes food intake, absorption, assimilation, biosynthesis, catabolism and excretion. 

• The fibre in diet contains substances like cellulose, lignin and pectin and cannot be digested by the action of digestive enzymes.
  
• Fibres in food can be classified into two types-
  

Diapedesis is the specific physiological process where white blood cells, particularly neutrophils, migrate through the endothelial walls of capillaries to reach sites of infection or tissue damage.