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BIOL1008 > Digestive System > Flashcards

Digestive System Flashcards

1
Q

What are the parts which are part of the GI tract (alimentary canal)?

A

Oral cavity
Pharynx (part of throat)
Oesophagus
Stomach
Small intestine
Large intestine

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2
Q

What are accessory organs

A

Structures which help with mechanical or chemical digestion

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3
Q

What are the accessory organs

A

Teeth
Tongue
Salivary glands
Liver
Gallbladder
Pancreas

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4
Q

What are the four layers of the GI tract (oesophagus to anal canal)

A

Serosa/Adventitia

Muscularis externae

Submucosa

Mucosa

(Outside to inside)

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5
Q

What is the function of the serosa/adventitia

A

Thin layer of connective tissue containing blood vessels, fat etc. Helps GI tract slide against organs

The serous membrane (or serosa) is a smooth tissue membrane of mesothelium lining the contents and inner walls of body cavities, which secrete serous fluid to allow lubricated sliding movements between opposing surfaces.

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6
Q

What is the function of the muscularis externae

A

The muscularis externa is responsible for segmental contractions and peristaltic movement in the GI tract. These muscles cause food to move and churn together with digestive enzymes down the GI tract. The muscularis externa consists of an inner circular layer and a longitudinal outer muscular layer.

2 types of muscles help with contraction to move food along the tract

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7
Q

What is the function of the submucosa

A

Passageway for blood vessels and ___ to go into GI tract

The submucosa has subdivisions of connective tissue, lymph nodules, and nerve fibers. Its major functions are nutrition and protection.

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8
Q

What is the function of the mucosa

A

Several layers of tissue - epithelium which is close to lumen

The mucosa is the innermost layer, and functions in absorption and secretion. It is composed of epithelium cells and a thin connective tissue. The mucosa contains specialized goblet cells that secrete sticky mucus throughout the GI tract.

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9
Q

What are the main functions of the digestive system

A

Ingestion

Secretion

Motility

Digestion

Absorption

Protection

Elimination

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10
Q

What does ingestion involve

A

Intake of food into the mouth

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11
Q

What does secretion involve

A

Cells of GI tract and accessory glands. Acid, buffers, enzymes, hormones, mucus

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12
Q

What does motility involve

A

Mixing and propulsion resulting from contractions and relaxation of muscle fibres

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13
Q

What does digestion involve

A

Breakdown of food into absorbale components (chemical or mechanical digestion

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14
Q

What does absorption involve

A

Mainly in small intestine. Molecules pass into blood or lymph

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15
Q

What does protection involve

A

Mucus and acidic fluid protect against pathogens

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16
Q

What does elimination involve

A

Removal of wastes as faeces, undigested material, bacteria, old cells lining GI tract are

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17
Q

Organic compounds such as carbohydrates, proteins, lipids, nucleic acids

A
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18
Q

What is mechanical digestion

A

Involves the physical breakdown of food into smaller particles

I.e. breakdown of carbs, proteins, lipids (triglycerides)

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19
Q

What are the accessory organs of the oral cavity

A

Teeth, tongue and salivary glands

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20
Q

What is chemical digestion

A

It is assisted via enzymatic activity to form absorbable compounds such as monosaccharides, amino acids, fatty acids etc.

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21
Q

What are the 3 major pairs of salivary glands

A

Parotid (in front of ear)
Submandibular (under mandible)
Sublingual (under tongue)

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22
Q

What is the function of the oral cavity (4)

A

Ingestion (location for food to enter body which will eventually turn into bolus (ball of food))

Digestion (teeth used for mechanical digestion via mastication). Chemical digestion is done via action of two enzymes in saliva; salivary amylase and lingual lipase

Secretion (saliva secreted by salivary glands lubricates the food)

Protection (oral cavity prodvides an ideal habit for microbes, thus the saliva has anti microbial properties)

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23
Q

What is salivary amylase

A

Digests starch to maltose

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24
Q

What is lingual lipase

A

Digests triglycerides

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25
What is the anatomy of the pharynx
Funnel shaped tube of skeletal muscle between oral cavity and oesophagus
26
What is the function of the pharynx
Shared by two organ systems (digestive and respiratory systems) During swallowing, structures close to ensure bolus moves to the oesophagus I.e. ensures food isn't in the wrong tube
27
What is the anatomy of the oesophagus
It is a muscular tube around 25cm long, and the upper tube is made of skeletal muscle, middle tube is a mix of skeletal and smooth muscle, and lower is smooth muscle This allows upper to be voluntary, and lower to be automatic
28
What is the function of the oesophagus
Motility: Propulsion of bolus to stomach via peristalsis
29
What is peristalsis
Continuous waves of contraction and relaxation of muscles
30
Explain the anatomy of the stomach
J shaped chamber 4 main regions, with the most distal portion being the pylorus It has 3 layers of muscles (compared to 2 everywhere else) Has 2 sphincters (muscular valves) to prevent backflow (gastro-oesophageal sphincter, pyloric sphincter)
31
Explain the function of the stomach and how it functions
Mechanical digestion and motility Peristaltic contractions = ~3 /min to push bolus towards pylorus, grinding bolus into chyme Pylorus allows 1/10 of chyme it holds to pass through pyloric valve per contraction Contractions also close the pyloric valve, and remaining contents are propelled back (retropulsion)
32
What is chyme
the pulpy acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food.
33
What are the 3 steps to digestion in the stomach
1) Propulsion: peristaltic waves move from the fundus towards the pylorus 2) Grinding: the most vigorous persitalsis and mixing action occur close to the pylorus. The pyloric end of the stomach acts as a pump that delivers small amounts of chyme into the duodenum 3) Retropulsion: The peristaltic wave closes the pyloric valve, forcing most of the contents of the pylorus backward into the stomach
34
What are the unique anatomical features of the stomach
Mucosa extends towards the submucosa to columns of specialised secretory cells called gastric glands There are also 3 muscle layers in the muscularis externa compared to the 2 which is normal in the digestive tract
35
What are the 3 muscle layers in the muscularis externa of a stomach
Oblique layer Circular layer Longitudinal layer
36
What do gastric glands do
Secrete components of gastric juice They have important roles in chemical digestion, protection and absorption
37
What are the components of gastric juices
Gastrin Pepsinogen HCl Bicarbonate-rich mucous Gastric lipase Intrinsic factor
38
What does gastrin do
Hormone that stimulates secretion of HCl and pepsinogen
39
What does pesinogen do
Activated to pepsin in the presence of HCl Pepsin chemically digests proteins into peptides in the stomach
40
What does Hcl do
Denatures proteins, converts pepsinogen to pepsin Kills microbes
41
What does bicarbonate rich mucous do
Protects stomach wall from protein digestion and corrosion from Hcl
42
What does gastric lipase do
Digests triglycerides into fatty acids and monoglycerides
43
What does intrinsic factor do
It is needed for transporation and absorption of vitamin B12 in small intestine
44
What is the anatomy of small intestine
3-6m in length 3 regions: Duodenum (closest to stomach), jejunum (in between duodenum and ileum), ileum (closest to the large intestine)
45
What are the specialised features of the small intestine which allow for increased surface area for absorption
Villi - finger like projections of mucosa layer into the lumen Microvilli - hair like projections of enterocytes (absorptive cells) Ultimately all allow for a greater surface area for absorption in the guts
46
What is the function of the small intestine
Chemical digestion Motility Absorption in jejunum and ileum Chemical digestion largely occurs in the duodenum. All forms of organic compounds such as carbs, proteins lipids etc are digested in the small intestine Most digestive enzymes secreted from pancreas
47
Explain chemical digestion as a function of the small intestine
Largely occurs in the duodenum All forms of organic compounds are digested in the small intestine such as carbs, proteins, lipids and nucleic acids Most digestive enzymes are secreted from the pancreas by pancreatic juices
48
Explain motility as a function of the small intestine
Peristalsis (regular contractions of smooth muscle) moves chyme through intestinal tract at around 16 contractions per minute Segmentation is the most common motion in the jejunum - localised contractions and relaxations move chyme back and forth a few minutes, which promotes mixing, absorption of nutrients and water
49
Explain absorption as a function of the small intestine (jejunum, ileum)
jejunum: Electrolytes (Na+, Cl-, HCO3-) - 80% Water - 90% Vitamins Products of carbohydrate and protein digestion (95%) ileum: Water insoluble products of lipid digestion, fat soluble vitamins, cholestrol from micelles with bile salts. Components in micelle is transferred to enterocytes (absorptive cells).
50
WHat is the function of the liver in digestion
It secretes bile: bile salts and bilirubin
51
What are bile salts
Bile salts emulsify fats, and facilitates absorption of fat and cholestrol
52
What is bilirubin
A pigment that is a waste product from the breakdown of red blood cells in the liver. Gut microbes further breaks down bilirubin to other compounds and eliminated in faeces
53
What is the function of the gallbladder in the digestive system
Stores and concentrates bile by absorbing water and ions
54
What is the function of the pancreas in the digestive system
Endocrine cells release insulin and glucagon Exocrine cells secrete pancreatic juice
55
What does pancreatic juice contain and what does it do
Contains water, bicarbonate ions, pancreatic proteases, pancreatic amylase, lipases, nucleases
56
What do bicarbonate ions do
Neutralises HCL from stomach
57
What do pancreatic proteases do
This enzyme breaks down proteins in your diet. It also helps protect you from germs that may live in your intestines, like certain bacteria and yeast.
58
What does pancreatic amylase do
This enzyme helps break down starches into sugar, which your body can use for energy.
59
What do lipases do
Lipase is an enzyme the body uses to break down fats in food so they can be absorbed in the intestines.
60
What do nucleases do
Nuclease enzymes helps in digesting DNA and RNA present in our dietary substances.
61
What are the substrates and products of pancreatic amylase?
Substrates : starch products: maltose, maltotriose Comes from pancreatic juices
62
What are the substrates and products of pancreatic lipase?
Substrates: Triglycerides emulsified by bile salts Products: Fatty acids, monoglycerides Comes from pancreatic juices
63
What are the substrates and products of maltase?
Substrates: Maltose Products: glucose comes from brush border enzymes
64
What are brush border enzymes
The brush border contains several key enzymes that digest the products of luminal digestion to produce monosaccharides.
65
Explain the anatomy of the large intestine
~1.5m in length 4 major regions: caecum, colon, rectum, anal canal Internal anal sphincter (involuntary) External anal sphincter (voluntary)
66
What are the functions of the large intestine
Digestion Absorption Motility Elimination
67
Explain digestion as a function of the large intestine
Some digestion by resident bacteria. Insoluble carbohydrates broken down via fermentation --> SCFAs
68
Explain absorption as a function of the large intestine
Absorbs remaining water and electrolytes (Na+, Cl-) Absorbs vitamins synthesised by resident bacteria (vitamin B complexes, vitamin K) - this helps solidify faeces
69
Explain motility as a function of the large intestine
Haustral contractions in asecending and transverse colon. This occurs every 30 mins and each contraction lasts around 1 minute. It is similar to segmentation in the small intestine but less frequent and slower. Aids with mixing and water absorption Peristalsis occurs 3-4 times/day. This allows for mass movement of content towards rectum
70
Explain elimination as a function of the large intestine
Formation of solid or semi solid material (faeces) Faecal material stored in rectum until enouhg accumuates to initiate defacation reflex Expelling of faeces via anus
71
Why is slow delivery of chyme from stomach to small intestine important
Slow delivery of chyme prevents rapid movement of water from blood to intestinal lumen. It is also allows for greater absorption of nutrients?!
72
LO: Describe anatomy and functions of structures within digestive system
GI tract: oral cavity, pharynx, oesophagus, stomach, small intestine, large intestine Accessory organs: teeth, salivary glands, liver, gallbladder, pancreas Other structures: sphincters
73
LO: Describe layers of gastrointestinal tract and specialised modifications in the stomach and small intestine
Mucosa, submucosa, muscularis externa, serosa/adventitia Gastric glands, villi, microvili
74
LO: Describe function of digestive enzymes
Salivary and pancreatic amylase ; lingual, gastric and pancreatic lipase; pepsin, maltase
75
LO: Discuss importance of slow delivery of chyme from stomach to small intestine
76
LO: Analyse the role of different digestive secretions in the processes of protection, chemical digestion and absorption and predict potential impacts of inadequate or excess secretion
Gastric juice: gastrin, pepsinogen, HCl, bicarbonate ions Bile, pancreatic juice
77
LO: Understand how nutrients and water are absorbed
Products of carbs, protein and lipid digestion
78
LO: Describe waste products from our digestive system; how these are made and how they are eliminated
Bilirubin Faeces
79
What is maltase and its function
80
What is maltose and its function

BIOL1008 (17 decks)

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