msnickelbiology12.weebly.com · Web viewSecreting pepsin in the inactive form, pepsinogen, protects the cells of the gastric glands _____ helps protect the stomach lining from both

Bio 12 Unit I – Digestion Digester:

ObjectivesCore:

• I can describe the __________________ and ____________________ of the digestive tract.• I can outline the chemical digestion of the 3 main ___________________________________________• I can explain the absorption process and refer to relevant structures (__________________).• I can explain how the ________________________ supports the digestive system.

Advanced:• I can explain homeostasis of _________________________________.

Introduction• Getting Their Fill of Krill• Whales are one of the largest animals in the world, it takes an enormous amount of food to support a 72-ton

humpback whale• These marine mammals eat small fishes and crustaceans called krill• Humpback whales strain their food from seawater using large plates called baleen, which they have on each side

of their upper jaw act like a sieve• In a typical day, the whale’s digestive system will process as much as 2 tons

of fish and krillObtaining and Processing Foods

• Animals ingest their food in a variety of ways• Animal diets are highly varied, and include

- ______________________________, plant-eaters (cattle, gorillas, snails, sea urchins) - Carnivores, meat-eaters (lions, hawks, spiders, snakes)

- Omnivores, eating ______________ plants and other animals (crows, cockroaches, raccoons, humans!)Animal feeding mechanisms

• __________________________: extract food particles suspended in the surrounding water (whales, clams, oysters, sponges!)

• Substrate feeders: live on their food source and eat their way through it (caterpillars and worms)• ___________________________: obtain food by sucking nutrient-rich fluids from a living host, either plant or

animals (Aphids, mosquitoes (female only) – males live off plant nectar!) Hummingbirds – benefit for their host• Bulk feeders: meaning they ingest relatively large pieces of food.

Food processing occurs in four stages1. _____________________________________________________2. _____________________________________________________3. _____________________________________________________4. _____________________________________________________

Four stages• Ingestion: The act of eating• Digestion: is the breaking down of food into molecules small enough for the body to absorb• Typically occurs in two stages: ________________________ digestion and __________________ digestion• Hydrolysis for chemical digestion, where water and enzymes are used to catalyze the reaction

• Proteins, fats, and carbohydrates are too big to pass through the cell membrane therefore it must be broken down.

• See chart polymers are broken down into monomers!Four stages

• Absorption: the cells lining the digestive tract take up (________________________________) the products of digestion like amino acids and simple sugars.

• These nutrients enter into the blood to the body cells where they can be joined to make macromolecules of the cells or broken down further for energy.

• ____________________________________: undigested material passes out of the digestive tract

Digestion occurs in specialized compartments• Food vacuoles are digested in compartments which house

_______________________ enzymes• Animals have a variety of ways to digest their foods;• Sponges digest their food entirely in food vacuoles• Cnidarians and flatworms have

________________________________ cavities with a single opening• Most animals have a __________________________________ canal, a digestive tube with two openings

_____________________________ canal• Food enters the mouth, pharynx, esophagus, crop, stomach(s),

gizzards, intestine, and anusHuman Digestive system

• The human digestive system consists of an alimentary canal and accessory glands

• The _________________________ muscle contractions of _____________________________ which squeeze food toward the stomach along the alimentary canal

• The pyloric sphincter: regulates the passage of food from the stomach to the small intestine

Digestion occurs in the oral cavity• The teeth break up food, saliva moistens, and

_____________________________ begin the hydrolysis of starch• The tongue pushes the bolus of food into the ___________________________________

The Pharynx • The food and breathing passages both open into the pharynx• The ______________________________________________ • Moves food from the pharynx into the esophagus, while keeping it out of the _________________

Connection• The Heimlich maneuver can save lives• The Heimlich maneuver: can dislodge food from the pharynx or trachea during choking• Peristalsis• The esophagus squeezes food along to the stomach by peristalsis• Peristalsis in the esophagus moves food into the stomach by using muscles contractions from

_________________________________________ to create a wave and push the bolus to the stomachGastric Juices

• The stomach stores food and breaks it down with acid and enzymes• _____________________________ in the gastric juice begins the

hydrolysis of protein• Gastric juice is made up of mucus and enzymes and strong acid• mixes with food to produce acid ________________________

Gastric juices• The gastric glands have three types of cells that secrete different

components of the gastric juice• 1. ________________________________ cells (dark pink) secrete

mucous, which lubricates and protects the stomach lining• 2. ___________________________ cells (yellow) secrete hydrochloric

acid (HCl)• 3. _________________________ cells (tan) secrete pepsinogen, an inactive form of the enzyme pepsin.

Pepsin1. Pepsinogen and HCl are secreted into the ______________________ (cavity) of the stomach2. The HCl converts the pepsinogen to pepsin3. Pepsin then activates more pepsinogen in a chain reaction as a _____________________ feedback loop

Regulation• Secreting pepsin in the inactive form, pepsinogen, protects the cells of the gastric glands• _______________________ helps protect the stomach lining from both pepsin and acid• Cells in our gastric gland do not secrete gastric juice constantly, their activity is regulated by a combination of

______________________ and hormones• When you see, smell, or taste food, your brain signals your stomach to _______________ gastric juice• When food is in your stomach, gastrin hormones are released in your bloodstream to secrete gastric juices

Regulation cont’d• A ____________________________________________

mechanism inhibits the secretion of gastric juices when the stomach contents become too acidic.

• The acid inhibits the secretion of gastrin, thus gastric juices• Your stomach churns every 20s producing the acid chime which is

a nutrient broth of digested food• GERD – ____________________________________________

reflux disease (chronic heartburn)Acid Chyme

• Pyloric sphincter helps regulate the passage of acid chyme in squirts into the small intestine• This can take 2-6 hours to empty after a meal• An acid chime rich in fats slows the squirting down to allow for slower digestion and more digestive enzymes to

be released

• As you will see, there are other enzymes released from your __________________________________ and pancreas to aid in digestion

Ulcers• Bacterial infections in the stomach and duodenum are associated

with ulcers from the bacteria _____________________________________

• They are tolerant of the low pH of the stomach and eat away and burrow into stomach linings.

• Your white blood cells cause _______________________________________ and your body can’t keep up with the loss of cells and replace them before a hole develops

• This hole, or ulcer, can become very dangerous.The small intestine

• The small intestine is the major organ of chemical digestion and nutrient absorption• The small intestine has a length over _________________ and about 2.5cm diameter• Nutrients enter into the bloodstream through the small intestine with the aid of two glandular organs• The __________________________________• The __________________________________

The Pancreas • The pancreas produces a mixture of digestive enzymes and an alkaline solution rich in bicarbonate• The alkaline solution ___________________________________ the very acid chyme from the stomach• The major enzymes produced in the pancreas include;• Pancreatic ___________________________ (maltose and other dissacharides)• ___________________________ & ______________________________• ____________________________ & nucleosidases• _____________________________________________• These enzymes are secreted into the small intestine, specifically the duodenum (first 25 cm)

The Liver• The liver performs a wide variety of functions, including the production of bile.• Bile contains bile salts that ______________________ fats• Increase surface area, which allows digestive enzymes to attack fat droplets easier• The gallbladder stores ______________________ is until it is needed

Enzymes and Digestion• Know the enzymes in the chart!• ________________________________ – digests milk sugar, children>adults

Protein digestion• The small intestine completes the digestion of proteins that began in the stomach.• The pancreas and the _____________________________ secrete hydrolytic enzymes that completely dismantle

polypeptides into amino acids• The enzyme trypsin and chymotrypsin break polypeptides into small polypeptides• Aminopeptidases and carboxypeptidase split off one amino acid at a time• __________________________________ hydrolyzes fragments of two or three a.a long

The small intestine structure• Structurally, the small intestine is well suited for its task of

_____________________________ nutrients.• Its surface area is huge ~300m2 (size of a tennis court)• It has a series of folds and projections that are circular in

structure• These finger-like projections are called

___________________________• Each of the epithelial cells lining a villus has many tiny

surface projections called microvilli• These extend into the lumen of the small intestine which

contributes to the high surface areaThe small intestine cont’d

• Some nutrients are absorbed by simple diffusion; others are pumped against their concentration gradient into the _________________________ cells

• The small _______________ vessel (yellow) and network of capillaries (red, purple, and blue) penetrate the core of each villus.

• Fatty acids and glycerol are transported into the _______________________• Other absorbed nutrients, like amino acids and sugars pass into the capillaries.

The small intestine cont’d• The capillaries that drain away nutrients from the villi converge into larger veins and eventually into a main

vessel, the _____________________ portal vein, that leads directly to the liver• The liver converts many of these nutrients into substances the body needs, like glycogen.• The liver also _____________________________ any toxins ingested

The Large Intestine • The large intestine, also known as the colon, is 1.5m long and 5cm in diameter• There is a small ‘_________________________’ called the cecum which is the start of the large intestine

• There is also a finger-like extension called the appendix which houses white blood cellsThe Large Intestine cont’d

• The main job of the large intestine is to absorb _____________________________• About 7L of fluid enters the lumen and approx. 90% is absorbed back into the blood and tissue fluids.• As the water is reabsorbed, the remains of the digested food become more solid and are called feces• Feces is mainly indigestible plant fibers and ___________________________ that live in the colon.• These bacteria, like E. coli are important as they help in digestion but produce important vitamins like biotin, folic

acid, several B vitamins and vitamin K.Eight Essential Amino Acids

• Vitamins and minerals• Are essential in the human diet• Most of these vitamins function as

____________________________________• A healthy diet includes these _____________ vitamins

Essential minerals are required for many body functions• Minerals are inorganic nutrients that play a variety of roles