The process of chemical breakdown begins in the mouth, and continues as the food moves through the digestive system(Fowler et al, 2013). In the stomach, powerful acids work together with enzymes to break food down into chyme, which is moved into the small intestine, where it is introduced to bicarbonate rich juices from the pancreas to make it safe for the rest of the digestive system, as well as intestinal flora in the large intestine, which help to break down cellulose, a material we otherwise would be unable to digest(Fowler et al, 2013).

Throughout the small intestine, villi, little tendrils, move the chyme along while pulling digested molecules into their cells to be carried through to the circulatory system, where they are dispersed through the body(Fowler et al, 2013).

Finally, the large intestine primarily serves to move the indigestible waste through to the anus for storage, and later expulsion, all while reabsorbing water and mineral salts used throughout the digestive process(Fowler et al, 2013).

Arteries are the blood vessel which moves blood away from the heart (Fowler et al, 2013). As the arteries move away from the heart, they branch out into smaller and smaller vessels, eventually becoming capillaries, where blood cells travel in single file, so as to allow for nutrient and waste transfer for the muscles and organs of the body (Fowler et al, 2013). Also of note for arteries further from the heart, these smaller arteries have more muscle surrounding them to allow for constriction of blood flow.

Once the blood reaches the organs and muscles, the blood is sent back to the heart through veins (Fowler et al, 2013). Veins are fundamentally different from arteries in that they have thinner vessel walls, due to the lower blood pressure, and they have valves throughout their length to prevent blood from backflowing (Fowler et al, 2013).

Gamete production in males begins at puberty, and is called spermatogenesis; this is an ongoing process of gamete production (Fowler et al, 2013). A stem cell undergoes mitosis, producing one stem cell and one spermatocyte (Fowler et al, 2013). The two spermatocytes undergo meiosis 1 to produce two secondary spermatocytes, which divide after meiosis 2, each producing two spermatids; as the four spermatids reach the lumen of the tubule, they grow flagellum, at which point they are proper sperm (Fowler et al, 2013).

Gamete production in females differs, as stem cells called oogonia undergo mitosis repeatedly in order to produce several million of them (now called oocytes) before birth (Fowler et al, 2013). They all begin the process of meiosis (also before birth), but stall the process in prophase 1 until puberty, whereupon endocrine hormones start the process of several follicles to develop in the ovaries each month (Fowler et al, 2013). From this point, the oocytes in the follicles finish their first round of meiosis, producing unequal daughter cells, with one daughter generally not surviving (Fowler et al, 2013). The surviving daughter cell is called the secondary oocyte, which is moved into the uterus, where it begins meiosis again, this time freezing in metaphase 2 until it is either fertilized or shed (Fowler et al, 2013).