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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
Q

What is the anatomy of the pharynx

A

Funnel shaped tube of skeletal muscle between oral cavity and oesophagus

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26
Q

What is the function of the pharynx

A

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

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27
Q

What is the anatomy of the oesophagus

A

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

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28
Q

What is the function of the oesophagus

A

Motility: Propulsion of bolus to stomach via peristalsis

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29
Q

What is peristalsis

A

Continuous waves of contraction and relaxation of muscles

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30
Q

Explain the anatomy of the stomach

A

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)

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31
Q

Explain the function of the stomach
and how it functions

A

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)

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32
Q

What is chyme

A

the pulpy acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food.

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33
Q

What are the 3 steps to digestion in the stomach

A

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
Q

What are the unique anatomical features of the stomach

A

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
Q

What are the 3 muscle layers in the muscularis externa of a stomach

A

Oblique layer
Circular layer
Longitudinal layer

36
Q

What do gastric glands do

A

Secrete components of gastric juice

They have important roles in chemical digestion, protection and absorption

37
Q

What are the components of gastric juices

A

Gastrin
Pepsinogen
HCl
Bicarbonate-rich mucous
Gastric lipase
Intrinsic factor

38
Q

What does gastrin do

A

Hormone that stimulates secretion of HCl and pepsinogen

39
Q

What does pesinogen do

A

Activated to pepsin in the presence of HCl

Pepsin chemically digests proteins into peptides in the stomach

40
Q

What does Hcl do

A

Denatures proteins, converts pepsinogen to pepsin

Kills microbes

41
Q

What does bicarbonate rich mucous do

A

Protects stomach wall from protein digestion and corrosion from Hcl

42
Q

What does gastric lipase do

A

Digests triglycerides into fatty acids and monoglycerides

43
Q

What does intrinsic factor do

A

It is needed for transporation and absorption of vitamin B12 in small intestine

44
Q

What is the anatomy of small intestine

A

3-6m in length

3 regions: Duodenum (closest to stomach), jejunum (in between duodenum and ileum), ileum (closest to the large intestine)

45
Q

What are the specialised features of the small intestine which allow for increased surface area for absorption

A

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
Q

What is the function of the small intestine

A

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
Q

Explain chemical digestion as a function of the small intestine

A

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
Q

Explain motility as a function of the small intestine

A

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
Q

Explain absorption as a function of the small intestine (jejunum, ileum)

A

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
Q

WHat is the function of the liver in digestion

A

It secretes bile:

bile salts and bilirubin

51
Q

What are bile salts

A

Bile salts emulsify fats, and facilitates absorption of fat and cholestrol

52
Q

What is bilirubin

A

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
Q

What is the function of the gallbladder in the digestive system

A

Stores and concentrates bile by absorbing water and ions

54
Q

What is the function of the pancreas in the digestive system

A

Endocrine cells release insulin and glucagon

Exocrine cells secrete pancreatic juice

55
Q

What does pancreatic juice contain and what does it do

A

Contains water, bicarbonate ions, pancreatic proteases, pancreatic amylase, lipases, nucleases

56
Q

What do bicarbonate ions do

A

Neutralises HCL from stomach

57
Q

What do pancreatic proteases do

A

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
Q

What does pancreatic amylase do

A

This enzyme helps break down starches into sugar, which your body can use for energy.

59
Q

What do lipases do

A

Lipase is an enzyme the body uses to break down fats in food so they can be absorbed in the intestines.

60
Q

What do nucleases do

A

Nuclease enzymes helps in digesting DNA and RNA present in our dietary substances.

61
Q

What are the substrates and products of pancreatic amylase?

A

Substrates : starch

products: maltose, maltotriose

Comes from pancreatic juices

62
Q

What are the substrates and products of pancreatic lipase?

A

Substrates: Triglycerides emulsified by bile salts

Products: Fatty acids, monoglycerides

Comes from pancreatic juices

63
Q

What are the substrates and products of maltase?

A

Substrates: Maltose

Products: glucose

comes from brush border enzymes

64
Q

What are brush border enzymes

A

The brush border contains several key enzymes that digest the products of luminal digestion to produce monosaccharides.

65
Q

Explain the anatomy of the large intestine

A

~1.5m in length

4 major regions: caecum, colon, rectum, anal canal

Internal anal sphincter (involuntary)

External anal sphincter (voluntary)

66
Q

What are the functions of the large intestine

A

Digestion

Absorption

Motility

Elimination

67
Q

Explain digestion as a function of the large intestine

A

Some digestion by resident bacteria. Insoluble carbohydrates broken down via fermentation –> SCFAs

68
Q

Explain absorption as a function of the large intestine

A

Absorbs remaining water and electrolytes (Na+, Cl-)

Absorbs vitamins synthesised by resident bacteria (vitamin B complexes, vitamin K) - this helps solidify faeces

69
Q

Explain motility as a function of the large intestine

A

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
Q

Explain elimination as a function of the large intestine

A

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
Q

Why is slow delivery of chyme from stomach to small intestine important

A

Slow delivery of chyme prevents rapid movement of water from blood to intestinal lumen.

It is also allows for greater absorption of nutrients?!

72
Q

LO: Describe anatomy and functions of structures within digestive system

A

GI tract: oral cavity, pharynx, oesophagus, stomach, small intestine, large intestine

Accessory organs: teeth, salivary glands, liver, gallbladder, pancreas

Other structures: sphincters

73
Q

LO: Describe layers of gastrointestinal tract and specialised modifications in the stomach and small intestine

A

Mucosa, submucosa, muscularis externa, serosa/adventitia

Gastric glands, villi, microvili

74
Q

LO: Describe function of digestive enzymes

A

Salivary and pancreatic amylase ; lingual, gastric and pancreatic lipase; pepsin, maltase

75
Q

LO: Discuss importance of slow delivery of chyme from stomach to small intestine

A
76
Q

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

A

Gastric juice: gastrin, pepsinogen, HCl, bicarbonate ions

Bile, pancreatic juice

77
Q

LO: Understand how nutrients and water are absorbed

A

Products of carbs, protein and lipid digestion

78
Q

LO: Describe waste products from our digestive system; how these are made and how they are eliminated

A

Bilirubin

Faeces

79
Q

What is maltase and its function

A
80
Q

What is maltose and its function

A

BIOL1008 (17 decks)

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