Chapter 23 - Digestive System

1. What is an enzyme

2. What are the branches of the ANS?

a. A protein catalyst that speeds up reactions, without being changed by the reaction

b. SNS, PNS, and the enteric nervous system (digestive system has its own nervous system)

Overview:

1. Alimentary canal –

2. Accessory digestive organs –

1. (digestive tract) the tube that food passes through as it goes from your mouth to your anus – mouth, esophaus, stomach, small intestine, large intestine

2. these organs play a role in digestion, but are not something that the food passes through (teeth, salivary glands, the liver, gall bladder, pancreas, etc)

What is the order of the processes involved in digestion?

6 in order

Ingestion

Propulsion

Mechanical breakdown

Digestion

Absorption

Defacation

Processes involved in digestion:

1. Ingestion – ___________

2. Propulsion – _____________

i. When food leaves your mouth and is a chunk = _______

ii. When food leaves your mouth and is a sort of past = _______

b. Peristalsis – ___________

3. Mechanical breakdown

i. – taking a piece of food and _______________________

ii. Mouth – chewing and breaking food down

iii. Stomach – churning and using acid and enzymes to further break food down

b. Segmentation – ______________

4. Digestion (chemical) – ___________________(include examples )

5. Absorption – primarily happens in ____________; some in the stomach and large intestine

6. Defecation – _____________

Processes involved in digestion:

1. Ingestion – bringing food/nutrients into your mouth

2. Propulsion – the movement of the things you’ve eaten, through your digestive tract

i. When food leaves your mouth and is a chunk = ebolus

ii. When food leaves your mouth and is a sort of past = chyme

b. Peristalsis – rhythmic movement of ingested things from the mouth to the anus

3. Mechanical breakdown

i. – taking a piece of food and breaking it into smaller pieces

ii. Mouth – chewing and breaking food down

iii. Stomach – churning and using acid and enzymes to further break food down

b. Segmentation –

i. Small intestine starts to break chyme down into smaller pellets and gets moved through the intestines

4. Digestion (chemical) – breaking chemical bonds; taking larger molecules and breaking them down into smaller molecules (proteins  amino acids, starches  simple carbs, etc)

5. Absorption – primarily happens in small intestine; some in the stomach and large intestine; where the body takes the nutrients and things that it needs

6. Defecation – removal of waste products

Serous Membrane of the Digestive System

1. Peritoneum

a. Visceral – _____________

b. Parietal – _______________

c. Peritoneal space – space between the two layers

2. Mesentery – ____________________________

a. Functions

i. where ________________that work alongside the digestive system are found_

ii. ____________________ - connects to all the organs of the digestive system and the wall of the abdominal cavity

iii. Location of some _________________________

3. Peritonitis – inflammation of the peritoneum; especially when there is not enough fluid between the layers

Serous Membrane of the Digestive System

1. Peritoneum

a. Visceral – rests against the surface of the organs

b. Parietal – lines the abdominal cavity

c. Peritoneal space – space between the two layers

2. Mesentery – extension of the peritoneum – two layers together (4 layers in the whole membrane)

a. Functions

i. __where blood vessels and nerves that work alongside the digestive system are found_

ii. Anchors the organs of the digestive system - connects to all the organs of the digestive system and the wall of the abdominal cavity

iii. Location of some fat storage__

3. Peritonitis – inflammation of the peritoneum; especially when there is not enough fluid between the layers

What are the functions of the mesentery

i. __where blood vessels and nerves that work alongside the digestive system are found_

ii. Anchors the organs of the digestive system - connects to all the organs of the digestive system and the wall of the abdominal cavity

iii. Location of some fat storage__

Histology of the Alimentary Canal

1. Mucosa – lines the _______ of the alimentary canal

2. Submucosa – wraps around _______________

3. Muscularis externa – two layers of _____________ (one layer runs ____ and one layer runs the ______) allows us to ______________(functions)______________

i. This allows for ______ and ________– when you squeeze, it propels whatever is inside, forward, and if you shorten, you grab whatever is inside to move it forward

b. Sphincters – muscular structures that ___________________; they act like ___ that open and close to control movement through different sections

4. Serosa – tough connective tissue that covers the organ; it is the entry point for ____________(3)______________

Histology of the Alimentary Canal

1. Mucosa – lines the lumen (the hollow cavity) of the alimentary canal

2. Submucosa – wraps around the mucosal layer

3. Muscularis externa – two layer smooth muscle (one layer runs circular and one layer runs the length) allows us to squeeze, adjust the diameter, and shorten or lengthen whatever organ we are talking about

i. This allows for peristalsis and segmentation– when you squeeze, it propels whatever is inside, forward, and if you shorten, you grab whatever is inside to move it forward

b. Sphincters – muscular structures that regulate the passage of things moving through the digestive system; they act like valves that open and close to control movement through different sections

4. Serosa – tough connective tissue that covers the organ; it is the entry point for nerve, blood vessels, and lymphatic vessels

Splanchnic Circulation – digestive system circulation

1. Celiac trunk – coming off of the _____, it brings blood to the ________

2. Mesenteric arteries – the place where __________________ pass through

Splanchnic Circulation – digestive system circulation

1. Celiac trunk – coming off of the aorta, it brings blood to the digestive organs

2. Mesenteric arteries – the place where blood vessels pass through

Splanchnic Circulation – digestive system circulation

3. Hepatic portal circulation -

a. What is a “portal vein” –______________________

i. Normal blood flow (one capillary bed only):

1. Heart → arteries → capillaries → veins → back to heart

ii. Portal circulation (special shortcut):

1. Heart → arteries → __________ → _______ → _________ → vein → back to heart

iii. Key point:

1. The portal vein is the middle vein that sits between two capillary beds (instead of going straight back to the heart after the first set of capillaries).

2. All organs in the digestive tract have veins that carry everything that we picked up from those organs. From there, instead of that blood going back to the heart, it goes into a portal vein that leads to the ____

a. at the liver, the liver takes its share of ____ (makes majority of proteins in the plasma), and also________________ that comes in. It metabolizes whats useful and if its harmful, it metabolizes that into something less harmful

3. Hepatic portal circulation -

a. What is a “portal vein” – the vein in the middle between two capillary beds (plays a big role in liver function)

i. Normal blood flow (one capillary bed only):

1. Heart → arteries → capillaries → veins → back to heart

ii. Portal circulation (special shortcut):

1. Heart → arteries → 1st capillary bed → portal vein → 2nd capillary bed → vein → back to heart

iii. Key point:

1. The portal vein is the middle vein that sits between two capillary beds (instead of going straight back to the heart after the first set of capillaries).

2. All organs in the digestive tract have veins that carry everything that we picked up from those organs. From there, instead of that blood going back to the heart, it goes into a portal vein that leads to the liver

a. at the liver, the liver takes its share of amino acids (makes majority of proteins in the plasma), and also filters everything that comes in. It metabolizes whats useful and if its harmful, it metabolizes that into something less harmful

4. Thinking Cap Question: Why is there a portal vein connecting from the spleen?

a. The spleen breaks down RBCs → sends bilirubin to the liver