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pharmacology > Digestive System: Structure and Function > Flashcards

Digestive System: Structure and Function Flashcards

1
Q

Describe the alimentary tract.

A
  • Tube extending from mouth to the anus
  • Muscular tube structure lined internally by epithelium
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2
Q

What is the function of the alimentary tract?

A

*Ingestion
*Processing
*Digestion
*Absorption
*Excretion

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3
Q

Describe the epithelium of mucosa membrane.

A
  • Type of epithelium differs with tissue function
  • Moistened by glandular secretions
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4
Q

Describe the lamina propria.

A
  • Loose connective tissue
  • Small blood vessels, lymphatics, nerve fibres
  • Immune cells e.g. macrophages and lymphocytes
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5
Q

Describe the muscularis mucosa

A
  • Thin muscle layer
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6
Q

What is the submucosa?

A
  • 2nd layer of loose connective tissue
  • Between mucosa and main muscle layers
  • Blood vessels, lymphatics, nerves
  • Neural tissue - submucosal plexus
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7
Q

What Is the function of the submucosal plexus?

A
  • Regulates contraction and glandular secretions
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8
Q

What is the muscularis externa and how is it divided?

A
  • Smooth muscle divided into two differentially orientated layers: inner circular layer and outer longitudinal layer
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9
Q

How is the muscularis externa arranged?

A
  • In layers which orientate in different directions; contractions propel materials along tract
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10
Q

Where is the second nerve plexus located?

A

Between muscle layers - myenteric plexus

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11
Q

What is outside of muscularis externa?

A
  • Adventitia and/or serosa
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12
Q

What is the alimentary canal suspended in and covered in and what does this allow?

A
  • Alimentary canal suspended in peritoneal cavity, covered in SEROSA
  • delimits adventitia from peritoneal cavity, allowing movement
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13
Q

What is the retroperitoneal organs covered in and what does this allow?

A
  • Retroperitoneal organs are covered in ADVENTITIA but NO SEROSA
  • holds organ structures together
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14
Q

What is the oral cavity?

A
  • Cavity lined by stratified squamous epithelium
  • Ingestion and fragmentation of food
  • Salivary glands
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15
Q

Where are the small salivary glands located?

A
  • in submucosa of oral cavity and tongue
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16
Q

What are the three main groups of the large salivary glands?

A

Sublingual: beneath tongue, many ducts
Submandibular: floor of mouth, inner surface of mandible, ducts behind teeth
Parotid : Largest, empties at the 2nd Molar

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16
Q

What are the three ways of administering drugs (oral activity)?

A
  • Oral
  • Sublingual
  • Buccal
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17
Q

Describe oral drug administration.

A
  • Given by mouth and swallowed
  • Easiest and safest method but slow absorption
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18
Q

Describe sublingual drug administration.

A
  • Placed under the tongue – dissolves in saliva
  • Rapid absorption, higher circulating levels
  • Not for bad-tasting or irritating medications
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19
Q

Describe buccal drug administration.

A
  • Placed in mouth next to cheek (tablet form)
  • Rapid absorption, higher circulating levels
  • Disadvantage -Possibility of swallowing the pill
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20
Q

Describe the structure and function of the oesophagus.

A
  • ~25cm long, through diaphragm to stomach
  • Contracts rhythmically toward stomach
  • Lower oesophageal sphincter: Prevents reflux,
    emesis and regurgitation
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21
Q

Describe the structure of the mucosa of the oesaphagus.

A
  • Above diaphragm: stratified squamous epithelium
  • Below diaphragm (~2cm) oesophagogastric
    junction: columnar epithelium
  • Defined lamina propria and muscularis mucosae
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22
Q

Describe the structure of the muscalaris externa of the oesphagus.

A
  • Striated muscle in upper one third
  • Mixture of striated and smooth muscle in middle
  • Smooth muscle lower one third
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23
Q

What is the lower digestive tract composed of?

A
  • Stomach
  • Small intestine (Duodenum, Jejunum, ileum)
  • Large intestine (Caecum, appendix, colon, rectum)
  • Many epithelial cell types - both absorptive & secretory
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24
Q

How is the efficiency of absorption improved?

A

By increasing surface area od contact between epithelia and lumen
– Intrusions/folding of epithelium (villi or plicae)
– Inversions (tubular structures), the lumen of which communicate with
main lumen
– Formation complex glands

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25
Q

What are the functions of the stomach?

A
  • Reservoir and Digestion
  • Mixes food with gastric juices to form a semifluid mass called chyme
  • Initiates protein breakdown and absorption of vitamin B12: release of
    intrinsic factor
  • Low absorption of nutrients or drugs
  • Highly lipid-soluble substances e.g. alcohol and some drugs absorbed
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26
Q

State the 4 anatomical regions of the stomach.

A

– CARDIA (closest to heart)
– FUNDUS (upper area)
– BODY (middle portion)
– PYLORUS (narrow bottom)

27
Q

Describe the structure of the gastric mucosa.

A
  • Columnar epithelium
  • Mucosa folded (Folds = RUGAE): Disappear when stomach distended
  • Shallow depressions on surface (GASTRIC PITS)
  • Entire mucosa has simple tubular gastric glands – open into gastric pits
28
Q

What do the cardiac glands produce?

A
  • Mucus producing glands - providing alkaline layer
29
Q

What are the 4 cell types for corpus-fundic glands?

A
  • Chief cells - pepsinogen, gastric lipase, chymosin
  • Parietal cells - gastric (hydrochloric) acid secreting and release intrinsic factor
  • Mucous neck cells
  • Endocrine - stimulate secretion of other cell types
30
Q

What is the pyloric gland made up of?

A

Endocrine cells more frequent, no chief cells

31
Q

What is achlorhydria?

A
  • Lack of gastric acid stomach
32
Q

What is dyspepsia?

A
  • Difficulty digesting food
33
Q

What is gastritis?

A

Stomach inflammation

34
Q

What is gastroenteritis?

A

Inflammation of stomach and small intestine

35
Q

What is haematemesis?

A

Vomiting of blood

36
Q

What is hiatal hernia?

A

Potrusion of the stomach through opening in diaphragm

37
Q

What are the three subdivisions of the small intestine?

A
  • Duodenum
  • Jejunum
  • Ileum
38
Q

What is the plicae?

A
  • folds of mucosa and submucosa (increase area x3)
    – Permanent structures (not distension dependent)
    – Absent from start of duodenum and distal ileum
39
Q

What is the intestinal villi?

A

– entire intestinal mucosa
– Increase surface area by x10
– Main cell type – Enterocyte- absorptive function

40
Q

What are microvilli?

A
  • Enterocytes, increase area by x20
41
Q

Describe the function of structure of tubular glands?

A
  • From base of villi through lamina propria to muscularis mucosae
    – Secretion of “intestinal juice”
    – Paneth cells at base of crypt – secretion, control of infection
42
Q

What is the function of goblet cells?

A

Secretion

43
Q

Describe absorption from small intestine.

A
  • Rich blood supply and large absorption area
  • Almost all digestion of protein, fat and carbohydrate
  • Most drug absorption occurs in the upper portion of the small intestine
  • Secretin released upon appearance of chyme in small intestine, stimulates release
    of bicarbonate (pancreas) to neutralise chyme
44
Q

Describe absorption in duodenum.

A

– Carbohydrates are broken down into simple sugars, proteins are broken down
– Fat emulsified by bile salts, broken down into free fatty acids and monoglyceride
by pancreatic lipase. Form micelles, which are absorbed;
– Most minerals (excl. Na+, K+ and Cl-) absorbed

45
Q

Describe absorption from jejunum.

A

– mono-saccharides, amino acids absorbed
– water-soluble vitamins (into bloodstream) fat-soluble vitamins (into lymph)

46
Q

Describe absorption in the ileum.

A

– Bile salts are reabsorbed
– Vitamin B12 absorption

47
Q

Describe the structure of the large intestine.

A
  • Surface relatively smooth – no plicae or villi
  • Crypts of Lieberkuhn – present and longer than Small Intestine
  • Goblet (mucous) cells more numerous than Small Intestine
48
Q

What are the main sections of the large intestine?

A

– CAECUM (including appendix)
* Appendix - large levels of lymphoid tissue
– COLON: Ascending, Transverse, Descending, Sigmoid
– RECTUM (including anal canal)

49
Q

What is the large intestine primarily involved in?

A
  • Absorption of fluids and electrolytes (Na+ , Cl- )
  • Secretion of electrolytes (K+ and HCO 3-) and mucus
  • Bacteria synthesize vitamin K and some B vitamins
  • Peristalsis slow and irregular
  • Formation, storage and periodic elimination of faeces
50
Q

What is defecation?

A
  • Faeces enters rectum
  • Rectum distends, stimulating mass peristalsis
  • Levator ani muscle relaxes
  • Internal and external sphincter muscles relax
  • Anus is pulled up and over faecal mass
  • Faecal mass is expelled
51
Q

Describe the absorption of water in GI tract.

A
  • Absorption of water is a passive process
    driven by the transport of solutes
    (particularly Na+) from the lumen of the
    intestines to the bloodstream
  • Water ingested and secreted is normally in
    balance with water absorbed
52
Q

State the 6 medications for digestive system and their function.

A
  • Antacid- Neutralises stomach acid
  • Antidiarrheal - Controls loose stools
  • Antispasmodic - Calms GI spasms
  • Antiemetic - Prevents regurgitation
  • Cathartic - Causes vomiting, or relieves constipation
  • Laxative - Relieves constipation
53
Q

What is the pancreas and state its functions?

A
  • Pink/Grey organ with no distinct capsule,
  • Retroperitoneal
  • Exocrine and Endocrine Functionality
54
Q

Describe the endrocrine functions of the pancreas.

A
  • islets produce and secrete insulin, glucagon, somatostatin
55
Q

Describe the exocrine functions of the pancreas.

A
  • Glandular secretion
  • Digestive enzymes; Trypsin/Chymotrypsin/Carboxypeptidase
    Pancreatic amylase and pancreatic lipases
56
Q

What are the 4 main cell types of the endocrine pancreas and describe them?

A
  • β -cells which secrete insulin (70%)
    – Stimulates glycogen, protein and fatty acid synthesis
    – Facilitates glucose uptake, lowers blood glucose
  • α-cells which secrete glucagon (20%)
    – Generally opposite to insulin, raises blood glucose
  • δ-cells which secrete somatostatin (5%)
    – Locally acting hormone, inhibits other endocrine cells
  • PP/F cells which secrete pancreatic polypeptide (2%)
    – Stimulates gastric chief cells, inhibits bile secretion
    – Inhibits pancreatic exocrine function
57
Q

What is the ductal system?

A

Acini duct - interlobular duct - intercalated duct - pancreatic duct

58
Q

How is glucagon secreted and what is its function?

A
  • Secreted by α-cells of endocrine pancreas
  • Prevents hypoglycaemia by elevating blood glucose levels
  • promotes glycogenolysis & gluconeogenesis
59
Q

What is glucagon stimulated and inhibited by?

A
  • Stimulated by cholinergic system, β-sympathetic fibres
  • Inhibited by glucose, insulin, somatostatin, α-sympathetic system
60
Q

How is insulin synthesised ad what does it do?

A
  • Synthesized in the β-cells of the islets of Langerhans
  • Direct effects upon carbohydrate, fat and protein metabolism
61
Q

How is insulin degraded and what is cellular activity controlled by?

A
  • By insulinase primarily in liver
  • By insulin receptors
62
Q

What does low glucose level lead to?

A

Decreased brain activity (glucose only fuel source)

63
Q

What does high glucose level lead do?

A

Osmotic water loss, damaged blood vessels, organ dysfunction etc.

64
Q

Where is somatostatin secreted?

A
  • by the δ-cells
65
Q

What does the secretion of somatostatin lead to?

A
  • Increased blood glucose
  • Increased blood amino acids
  • Increased blood fatty acids
  • Increased concentrations of upper GI hormones (Gastrin, Secretin, CCK, VIP)
    released in response to food intake
66
Q

What are the actions of somatostatin?

A
  • Acts locally within endocrine pancreas to depress insulin and glucagon
    secretion
  • Paracrine with glucagon to regulate insulin secretion
  • Decreases GI tract secretions and absorption
  • Decreased gastric, duodenal and gallbladder motility

pharmacology (40 decks)

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