Integumentary System

People are often interested in the appearance of their skin but rarely consider its functions. The integumentary system serves many purposes, including these important functions:

·         Protection- as long as the skin is intact and not inflamed; it is our first line of defense against the entry of bacteria and viruses. It also protects underlying structures from ultraviolet radiation and dehydration.

·         Body temperature regulation- skin plays a major role in regulating body temperature. When a person is hot, dermal blood vessels are more dilated so more blood pass through the skin. This is beneficial because blood carries a lot of the heat in the body. When the blood gets close to the skin the skin, the heat can escape. If someone is cold, the dermal blood vessels constrict, preventing the heat in the blood from escaping.

·         Vitamin D production- when exposed to sunlight, the skin produces a molecule that is turn into vitamin D. The body needs vitamin D for calcium absorption.

·         Sensation- the skin is packed with sensory receptors that can detect touch, heat, cold, and pain.

·         Excretion- small amounts of waste products, such as water and salts, are lost through skin when a person perspires. This is why hydration is so important when exercising or during exposure to high temperature, when the amount of perspiration increased and higher amounts of water and salts are lost.

The topmost layer of the skin is the epidermis. The dermis is the complex middle layer. The innermost layer attaching the skin to muscle is subcutaneous layer. The most common cell type in the epidermis is the keratinocyte. Keratin is a durable protein that makes the epidermis waterproof and resistant to bacteria and viruses.  Another cell type is the melanoctye , which makes the pigment of melanin and the amount of melanin you have in your skin makes up your skin color. The dermis contains sudoriferous (sweat) glands, sebaceous (oil) glands, hair follicles, the arrector pili muscles, collagen fibers, elastin fibers, nerve fibers, and many blood vessels. The subcutaneous layer of the skin or hypodermis, is largely made of adipose and loose connective tissue.

Digestive System

The digestive system uses mechanical and chemical mechanisms to break down food into forms that the body's cell can use. The pathway of food through alimentary canal starts with the mouth through the pharynx, esophagus, stomach, small intestine, large intestine, and anal canal. The mouth takes in food and the teeth assist in reducing its size through chewing the tongue mixes food and holds it between the teeth.The salivary glands produce saliva to assist in moistening and breaking down food. The pharynx is a long muscular tube extending form behind the nose to the esophagus  connecting to oral and nasal cavities, it also acts to push food into the esophagus. The soft palate rise, closing the opening between the nasal and oral cavities. The epiglottis covers the laryngeal opening  food is forced into the oropharynx by the tongue and the pharynx contract, pushing food to the esophagus. The esophagus is a muscular tube that pushes food toward the stomach through muscular contractions. At the end of esophagus is the cardiac sphincter, the entrance  to the stomach. The stomach receives foods, mixes it with gastric juices to start protein digestion, and moves food into the small intestine. The stomach has for regions: cardiac region, funds, body, and pylorus. The small intestine carries out most of the nutrient absorption. The sections of the small intestine are in order, duodenum, jujunum, and ileum. They secretes peptiases to digest protein; sucrase, maltase, and lactase to digest sugars; and intestinal lipase to digest fats. The components of the large intestine are the cecum with its vermiform appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal, ending in the anus. The large intestine's primary's job is to get rid of the body's solid waste by defecation. The liver stores vitamins and iron and produces macrophages to flight infections. the gallbladder stores the bile produce by the the liver. The pancreas produces pancreatic juices that assist in carbohydrate, lipid, and protein digestion. Nutrients absorbed by the body include carbohydrates, proteins, lipids, vitamins, minerals, and water. Most of the absorption takes place in the small intestine.