Lesson 13: What happens to the food you eat

Salvation

*Salivary glans secrete the saliva in the mouth and saliva is important because it makes it easier for food to go down the esophagus. Saliva also has salivary amylase which helps the breakdown of polysaddchride starches. *Secretion of the salivary glads are controlled by the nervous system. Secretion is always happening but when there is food, the secretion increases. Senses also increase secretion. **It's like when you think about food and your mouth waters.

Mouth

*This is the beginning of the chemical digestion. *The mouth holds the tongue which is used to mix food with saliva.

Variations in vertebrate digestive systems

All animals lack enzymes to digest celluluse so instead they have different digestive tracts that contain bacteria and proteins that convert cellulose to substances hosts can absorb.

Mouth and Teeth (general)

In most vertebrates (humans) have teeth that are used for chewing. However, birds dont have teeth so instead they break up food in a 2-chambered stomach. They have a gizzard with ingestion pebbles to grind up food.

Esophagus

It is a muscular tube that connects the pharynx to the stomach. Swallowing creates a one-directional waves of contraction in the muscles. The waves are called peristalisis and allow humans to swallow whatever position they may be in. Movement is controlled by a sphincter that opens in response to the pressure exerted by the food and makes sure food pumped into the stomach doesnt go back into the esophagus.

Stomach

Sac-like structure that can expand. It churns food with gastric juice (acidic secretion) which is made up of mucus HCL and pepsin. The stomach has a low pH to denature proteins to make them easier to digest. The mix of partially digested food and gastric juice is chyme. Chyme leaves the stomach to the small intestine

Gall Bladder

Stores the bile also is an accessory organ

Absorption of proteins and polysacchrides

Theses molecules come into contact with microvilli and the brush border enzymes break them down to amino acids and monosacchrides which are transported through epithelial cells and blood capillaries.

Large intestine (colon)

This deals with water absorption, electrolyte absorbtion, vitamin K absorption and compacts feces

Swallowing

This is a voluntary action (you do it on purpose) but then continued as an involuntary control. The process begins when the soft palate elevates to push against the back wall of the pharynx. This seals off the nasal cavity and prevents food from entering it. Pressure against the pharynx triggers the swallowing reflexes which is involuntary.

Liver

This is another accessory organ. It is the largest internal organ and is most metabolic. It deals with detoxification protein synthesis, portein synthesis, glycogen storage and bile production.

Submucosa

This is connective tissue in the digestive tract rich in blood with nerve fibers

Serosa

This is epithelial tissue in the digestive tract that protects the canal from harsh abrasions as wells flex and extend.

Muscularis

This is smooth muscle tissue in the digestive tract arranged in the circular and longitudinal layer to move food through canal

Mucosa

This is the innermost epithelial tissue the of digestive tract that secretes mucus and absorbs end products. It also protects underlying tissue

Small Intestine

This is where most digestion and absorption occurs. Most of the small intestine is the duodenum and the rest is divided into the jejunum and ileum. The duodenum deals with further breakdown of food. And the jejumum deals with absorbing the nutrients. There are microvilli on the small intestine that are referred to as brush border and increases the absorbency surface area.

Pancreas

This organ is known as an accessory organ that helps with digestion. the small intestine secretes pancreatic fluid into the duodenum through the pancreatic duct. So the pancreas is an exocrine gland. The pancreatic juice contains trypsin, chymotrypsin, pancreatic amylase, lipase, and bicarbonate. These enzymes are introduced inactive

Absorption of fats

bile salts help break down fats into fatty acids and monoglycerides. They are lipophilic so they diffuse across the membrane.

Minerals

inorganic compounds

Bolus

lump of food for easier processing

Hormonal control of feeding behavior

the control of feeding behavior is under long term control related to the amount of adipose tissue and short term control related to the act of feeding. The control is mediated by the CNS

Herbivore digestive tract

their digestive tracts are longer to allow more time to digest cellulose. They contain cecum which is the location where cellulose is digested.

Ruminant Herbivores (cow) digestive tract

they have 4 chamber stomachs w/ many bacteris and proteins.

Hormones involved with digestion

*Gatrin = released when food enters the stomach and stimulates the secretion of HCL and pepsinogen by stomach * CCK= released when fatty chyme is in the duodenum and stimulates the gallbladder contraction and secretion of digestive enzymes by pancreas. *GIP=released when fatty chyme is in the duodenum and inhibit stomach emptying. *Secretin= released when acidic chyme in duodenum and stimulates secretion of bicarbonate by pancreas.

Feces

Contain water, electrolytes, mucus, bacteria, bile pigment, and bacterial compounds

Liver and homeostasis

Chemically modifies substances before reaching the rest of the body. It converts dangerous toxins to urea which is safe and can be carried by the blood. It also regulates the levels of compounds in the body. Turns molecules into more soluble substances. It also produces proteins in the blood plasma.

Digestive enzymes

Look at chart on the activity

Bile

Made in the liver and stored in the gall bladder. Bile is made of bile pigments and bile salts. Bile pigments are waste products of broken down red blood cells. Bile salts disperse dumped lipids

Basic requirements of human nutrition

The primary functions of food are to provide a source of energy and raw materials. Calories are the unit used for food. All humans need proteins, carbohydrates, fats, vitamins, minerals and water.

Rectum

There are 2 sphincter muscles. One is voluntary and another is involuntary

Small animals digestive tract

These animals often don't have a cecum so they have to eat their own feces in order to obtain nutrients.

Fats

act as an energy storage

Proteins

essential amino acids. There are 9 amino acids that humans get from their food source.

Digestive system overview (very general)

food is ingested in the mouth and broken down to pass through the pharynx opening of the oral cavity. It goes to the esophagus and then to the stomach. From the stomach, partially digested food enters the small and large intestines where digested nutrients are absorbed and waste exits.

Carbohydrates

obtained from foods such as fruits, vegetables, and grains.

Vitamins

organic compounds. there are 13 essential vitamins in a human diet.