Biology 12 – Name: _____TEACHER__________

Date: _______________________

For ALL Organ Systems – the Key Concept / Driving Question is:

How does structure impact function and vice versa?Anatomy is the study of structures. Physiology is the study of functions.

Digestion – Part 1 – Structure and Function

Did you know?

•We eat about 500kg of food per year.

•We make approximately 1.7 liters of saliva every day.

•Every day 11.5 liters of digested food, liquids and digestive juices flow through the digestive system, but only 100 mL is lost in feces.

•Most of us pass somewhere between 200 and 2,000 ml of gas per day (average, about 600 ml) in roughly 13-14 passages.

•As a group, vegetarians produce more gas than meat-eaters because the intestinal enzymes can't digest the cellulose in vegetables' cell walls

•How big is your stomach ? An adult’s stomach holds about 1 liter of food. A child’s stomach holds a little bit less. Your stomach gets bigger the more you eat. A large adult can eat and drink up to 4 liters of food and liquid at one meal!

•How long are the intestines ? The small intestine is more than three times as long as the whole body ! In an adult, this is about 21 feet long. The large intestine is another 5 feet long. The whole tube from the mouth to the anus is about 30 feet long. Wow !

Huh!

Functions of the Digestive System: Ingest food Secretes (enzymes, bile, HCl) to assist in digestion Digest macromolecules (i.e. food) Absorbs food

to make energy and to help us grow and repair ourselves.

Eliminates indigestible waste

Four Steps of Digestion include:

1. Ingestion of food in mouth2. Mechanical & Chemical digestion3. Absorption of molecules4. Elimination of indigestible substances

Mechanical digestion– Large pieces of food become smaller ones without creating a new product– Example:

Chewing of food in the mouth & Churning and mixing of food in the stomach

Chemical digestion– Enzymes chemically break down macromolecules into new smaller new products that can be absorbed. - Example:

polymer → monomerstarch -> glucose

The PathwayImagine a hose or a hollow tube. Beginning at: Mouth -> Pharynx -> Esophagus -> Stomach -> Small Intestine -> Large Intestine-> Rectum->Anus is the End

With 3 Accessory Organs that assist in digestive process. They are:Liver, Gall Bladder, and Pancreas

Mouth / Oral Cavity (the beginning)

Functions1. Ingestion2. Begins digestion: Mechanical & Chemical

Structures (teeth, salivary glands and tongue)1. Teeth

- Begins mechanical digestion to increase surface area(SA) of food for enzymes to act upon.

2. Salivary Glands - are ducted glands that produce saliva, which:

a) Liquefies food and b) Contains salivary amylase which begins

chemical digestion (optimal @ pH 7)c) Lubricates and softens the BOLUS of food.

BOLUS (saliva + chewed food).d) Enzymes in saliva kill bacteria

3. Tongue:- is a muscle that does 3 functionsa) Contains taste budsb) Moves the food around in the mouthc) Pushes the BOLUS of the food to the back of the throat to the ‘swallow reflex centre’.

Next stop – The Pharynx

Its Function: = Swallowing = reflex action (no conscious thought) = Takes food from mouth to esophagus.

How? When food is placed on the ‘reflex center’: a) the soft palate covers nasopharynx b) the epiglottis covers the trachea (respiratory) c) peristalsis of the esophagus begins

Note: its impossible to breath/swallow at same time

Structure = region at the back of the throat

The Epiglottis

Structure & Function: A flap of tissue that covers the trachea when swallowing so food does not go down the trachea

Show video

The Esophagus

Function: - Moves the bolus (saliva & chewed food) from the pharynx to the stomach.- Food moves through the esophagus by PERISTALSIS - Peristalsis is a slow, rhythmic contraction that pushes the BOLUS along - (Note: Peristalsis continues down the length of the entire digestive tract.)

Structure: - A long muscular tube that connects the pharynx to the stomach. - No digestion occurs here.- At the beginning of stomach, there is a ring of muscle tissue called the cardiac sphincter that

stops the food in the stomach (acidic chyme) from re-entering the esophagus.-

The Stomach

Structure and Function: - A “J” shaped organ for food storage & digestion- Made up of 3 muscle layers that churn, mixes and liquefies food (mechanical digestion).

o This process is aided by the ridges or rugae in the stomach layer- Mucus secretions protect the lining of the stomach

o against HCl secretions o protein digestion that occurs here

- It begins the chemical digestion of proteins. The gastric glands in the stomach secrete gastric juice (chemical digestion).

- The stomach begins with the cardiac sphincter and ends with the pyloric sphincter.- The pyloric sphincter at the base of the stomach slowly releases the acidic chyme (food in

stomach) into the duodenum at a slow and controlled rate.

Stomach Gastric Juices: Contain

:

When Proteins enter the stomach, HCl is relased. This creates a pH of 2.5. The low pH - kills bacteria and denatures salivary amylase.- Transforms pepsinogen (inactive) to PEPSIN (active enzyme)

• An ULCER can result if acid penetrates the mucous layer and pepsin begins to digest stomach cells.

Digestion – Part 2 – 2018

Next stop ... Small Intestine:

Structure & Function :

Approx 6m long and 2 – 5 cm wide.

Split into 3 sections:1. Duodenum

1st 25 cm – receives secretions from the liver, gall bladder and pancreas chemical digestion of fats, carbs, lipids and nucleic acids takes place here

2. Jejenum: Middle section – both chemical digestion and absorption take place here

3. Ileum: absorption of the nutrients into the blood and lymph occurs here

Key structural features:- Has highly folded walls that increase the SA and therefore absorption in the SI. - S. I. is lined with VILLI. Villi contain:

• Blood capillaries for nutrient absorption (glucose, nucleotides & aa’s)• Lacteals (lymph capillaries) absorb glycerol & fatty acids

- The villi also have smaller folds called MICROVILLI.• The absorption through microvilli involves active transport and requires much energy (ATP).

- Physical and chemical digestion take place here.

Functions : - chemical digestion and physical digestion take place here.

- pancreatic and intestinal secretions complete the digestion of all the nutrient types. Organic molecules (polymers) ---> get broken down into monomer units so the absorption of nutrients can occur:

a) Proteins get broken down into amino acids (aa’s get absorbed into the blood stream)b) Carbohydrates ----> Glucose and other monomers of carbs (which enter into the blood stream)c) nucleic acids --->Nucleotides (into the blood stream)d) lipids ---> Fatty acids and Glycerol (into the lacteal = lymphatic system)

-for regulation of digestive secretions (by hormones and the nervous system) – read pages 269 and figure 9.5.

Accessory Organ # 1 -- The pancreas. The pancreas is a dual organ. It functions as both a:

1. ENDOCRINE GLAND - makes hormones insulin and glucagon.2. EXOCRINE GLAND - makes the enzymes to digest carbs, fats, proteins and nucleic acids.

1. Pancreas endocrine gland function :

- high blood sugar → insulin secreted; insulin removes glucose from the blood by:1. causing the liver to store the glucose as glycogen 2. promotes formation of fats3. causes cells to absorb glucose

- low blood sugar → glucagon secreted; 1. glucagon causes the liver to break down glycogen & release glucose back into the blood stream

2. Pancreas exocrine gland function :

- makes pancreatic juices. Pancreatic juices have 5 parts (memory trick: SALT + N):

1. Sodium Bicarbonate (NaHCO3) - a base that is released to neutralize the acidic stomach chyme (from pH 2.5 to pH 8.5)

2. Pancreatic Amylase - an enzyme that converts starch to maltose.

3. Lipase - an enzyme that converts lipids into fatty acids and glycerol

4. Trypsin - an enzyme that converts small protein chains into dipeptides and tripeptides.

5. Nucleases - enzymes that convert nucleic acids (DNA and RNA) into nucleotides.

At the beginning of the small intestine

there are 3 Accessory Organs = the Pancreas, Liver and Gall Bladder they are VERY important to help with the process of digestion, BUT they are NOT actually part of the

hollow tube/digestive system pathway.

The Pancreas and Gall Bladder connect to the small intestine

at the duodenum.

Plus water to hydrolyze these reactions

Accessory Organ # 2 -- The Gall Bladder.

The Gall Bladder is connected to the Liver and the Small Intestine. It is a small sac shaped structure that functions to store excess BILE and send BILE to the SI via the bile duct. NOTE: (1) BILE is NOT an enzyme.

(2) Bile, made in the liver, helps in the PHYSICAL digestion of Lipids. It breaks to lipids down into smaller particles -- called Emulsification.

Accessory Organ # 3 -- The Liver.

It has many functions ... that we’ll talk about later.

Pictured below -- relationship between the liver, pancreas and blood glucose levels in the bloodstream. (See also p272 figure 9.9.)

Let’s summarize!!

At the beginning of the Duodenum – the liver, pancreas and gall bladder secrete hormones, enzymes and bile to continue the chemical and physical digestion process.

The specific function of the small intestine is

One:

Two:

Next stop ...

The Cecum: = blind end of large intestine where it meets small intestine

The Appendix:= projects from the cecumHas lymph tissue to help fight infection• Subject to inflammation = appendicitis which means it may need to be removed

The Large Intestine

Structure:

Functions :

1) Main function = Absorption of the water and salts (90 – 95% of water reabsorbed here) 2) stores indigestible material until it can be eliminated3) It also has anaerobic bacteria, E.Coli, that:

a. eat the wastes and produce useful things that we need to survive (ie: vitamin K and amino acids)

b. produce growth factors (proteins that stimulate cell growth)c. these bacteria produce waste of their own (methane gas) Phew!

Rectum:- located at the end of the large intestine.- Is where “feces” are stored until evacuation - Defecation occurs when message is sent to

central nervous system to stimulate bowel movement. (Fig 9.7, p 270)

Anus:Sphincter muscle through with feces exits the body.

Did you know?At the Rectum & Anus, If wastes moves through the large intestine too quickly:• the intestines don’t have time to absorb enough water, the feces are liquefied, and you have diarrhea.

If feces moves through too slowly:• then too much water is absorbed and the feces become hard and you are constipated.

The END ... get it ... the END.

Now to test your knowledge ...1. Can you trace the path from mouth to anus? 2. What types of digestion take place at each location?3. How does each location’s structure help it to function?4. If you ate a slice of bread (assume it ONLY contains carbohydrates), trace the path of

chemical digestion from the mouth to the blood stream. In your answer include:i. Location and pHii. What is being digested? (e.g. starch -> maltose)iii. What enzyme is helping in the digestion?iv. Where is the enzyme produced?

5. Repeat question 4 with a piece of steak (assume it only contains proteins)6. Repeat question 4 for 2 tablespoons of olive oil.

Biology 12 – Name: _____TEACHER__________

Date: _______________________

Digestion – Part 2 – Accessory Organs for Digestion (Ch 9.2)Liver, Gall Bladder and Pancreas. (All you need to know about the Pancreas and Gall Bladder was covered in Part 1)

The Liver:

Hepatic Portal System – What is this? What does it do?• Nutrients absorbed from the small intestine are taken to the liver by the hepatic portal vein.• Liver stores excess glucose and glycogen, releasing it as needed.

The Liver: largest internal organ. blood from the villi travels via the hepatic

portal vein to the liver. liver acts as a ‘gatekeeper’ to the blood by

keeping levels of various nutrients in the blood constant.

Textbook: figure 9.10, p 273

Functions:

The Liver – 7 functions. Mostly involve what happens to the blood in the liver.(Table 9.2, p 273) (Memory trick – remember B.B.B.B.B.U.I&V)

1.Bile produced (review from part 1) – liver produces bile (stored in gall bladder). Bile emulsifies fats,

mechanically breaking fats into smaller pieces which increases the surface area of fats for digestion by lipase.

2.Blood Sugar

3.Blood detoxify Liver detoxifies harmful substances e.g. turns alcohol into fatty acids.

(Over time this can cause scarring of the liver tissue which gives rise to cirrhosis.)

4.Blood proteins produced

Makes blood plasma proteins from amino acids e.g. albumin (helps maintain the osmotic pressure of

the blood), fibrinogen (important for blood clotting)

5.Blood Cells (red) get broken down Liver destroys old red blood cells and

recycles hemoglobin

6.Urea – production

7.Iron and Vitamin Storage Liver stores iron and vitamins (A, D, E, K and B12)

Have covered in notes – make sure you know Chapter 9.3 – Digestive Enzymes

(review from part 1) – the liver regulates blood glucose levels by signaling the pancreas to release the required hormones insulin & glucagon

If blood sugar is high, insulin will signal liver to convert glucose -----> glycogen

If blood sugar is low, glucagon will signal liver to glycogen ----> glucose

If necessary the liver can convert / breakdown amino acids into glucose to maintain glucose concentration of the blood plasma.

o This process produces urea o Urea is removed by the kidneys in the

production of urine.