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Dentistry BDS1 Sem 2 > GIT > Flashcards

GIT Flashcards

1
Q

What is the main function of the digestive tract?

A

Contribution to homeostasis by absorbing water, minerals, secrete waste and breakdown food in order to create molecules that can be used for energy conversion.

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2
Q

What are the components of the GIT and what is there function?

A

Oral Cavity – biting, chew, swallow
Pharynx & esophagus – transport
Stomach – mechanical disruption (via muscular contraction); chemical digestion
Small intestine – chemical & mechanical digestion & absorption
Large intestine – absorption of electrolytes & vitamins
Rectum and anus – storage and excretion

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3
Q

What are the 6 basic processes of digestion and where are they carried out?

A
  1. Ingestion - mouth
  2. Mixing/propulsion – orthopharynx and peristalsis
  3. Mechanical Digestion - chewing
  4. Chemical digestion – enzymes and acid
  5. Absorption - intestines
  6. Excretion/Defecation – rectum and anus
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4
Q

What is the basic structure of the GIT?

A
  1. Mucosa
  2. Submucosa
  3. Muscularis
  4. Serosa
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5
Q

What connects the mucosa and submucosa?

A

Lamina propria – the connective tissue layer – contains MALT, nerves and used as route for nutrient absorption.

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6
Q

What epithelium lines most of the GIT?

A

Simple columnar epithelium in the small intestine and remainder of the tract.
Stratified squamous in the mouth, esophagus & anal canal.

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7
Q

What is the function of Goblet cell?

A

Mainly mucous release

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8
Q

What type of junction is connected between epithelial cells in the GIT?

A

Tight junctions

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9
Q

What is the muscularis externa?

A

It is a layer of muscles that are present in the GIT that are composed of mostly smooth muscles and sometimes skeletal muscles.

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10
Q

What is the autonomous smooth muscle function?

A
  1. Autonomous smooth muscle function – internal pacemaker activity – initiated of the interstitial cells of Cajal
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11
Q

What are intrinsic nerve plexuses?

A
  1. Intrinsic nerve plexuses – myenteric plexus between the two layers of the muscularis – submucosal plexus – both used to regulate local action
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12
Q

What are extrinsic nerves in the GIT?

A
  1. Extrinsic nerves – autonomic nervous system division – increase GIT function with increase parasympathetic pathway – coordinate activity between different regions of the tract
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13
Q

What is the function of GI hormones?

A
  1. GI hormones – released by enteroendocrine cells of the mucosa – released into the blood stream and act on nerves, muscle, glands – gastrin, secretin, cholecystokinin, GDIP, motilin
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14
Q

What is an esophagus?

A

It is a large muscular tube that transports from mouth to stomach. Non-keratinised stratified squamous epithelium. Same layers as remainder of GIT. Has submucosa glands that secrete fluid that helps with transport. Proximal end – skeletal muscles. Distal – smooth.

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15
Q

What is a stomach?

A

It is a C shaped sack that contain rugae for expansion. Starts at the esophagus and ends at the pyloric sphincter. Has normal layers of the GIT.

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16
Q

What is the mucosal layer of the stomach?

A

Simple columnar epithelium with gastric pits and glands. The layer that separates the mucosa from submucosa is the muscularis mucosa. All the columnar cells of the mucosa release alkaline mucus which is important for protection and defense. There are also glands that are able to produce acid, enzymes and hormones.

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17
Q

What are the three layers of the stomach histologically?

A
  1. Cardia – narrow circular band – mostly secretory cells that produce mucous & lysozymes
  2. Fundus and body – has fundic glands and most of acid producing cells
  3. Pylorus – very deep gastric pits – secrete mucus & lysozymes
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18
Q

What are mucous cells of the GIT and what is there significance?

A
  1. Mucous surface cells – produce insoluble mucous
  2. Mucous neck cells – produce thinner and more soluble mucous – irregular shape cells
    Both mucous cells produce mucous, a special coating that helps with protection of the stomach as well as not allowing the gastric juice to damage the stomach and “self-digest”.
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19
Q

What are parietal cells and where are they found?

A

Parietal cells are mainly found on the upper parts of gastric glands. Bright pink (eosinophilic). Resting or active. Secrete H+ and Cl- which combine to form HCl. Also secrete intrinsic factor for B12 absorption.

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20
Q

What are chief (zymogenic) cells?

A

They are cells that are mainly found in lower regions of glands. Synthesis protein. Have granules that contain inactive pepsinogen. Produce lipase.

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21
Q

What are the enteroendocrine (and paracrine) cells?

A

They are cells found in neck and base of gastric gland. Fundus of stomach secretes serotonin. Body of stomach secretes histamine. Pylorus of stomach secretes gastrin and somatostatin.

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22
Q

What are the three areas of the small intestine?

A

Duodenum (5%), jejunum (40%) and Ileum (60%)

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23
Q

What is the main difference between the lining of the small intestine and the lining of the stomach?

A

Small intestine has villi that are projections rather than rugae with gastric pits.

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24
Q

What are the features of the Ileum?

A

Smaller villi and presence of lymphatic nodules in the Ileum

25
Q

What are the enterocytes?

A

They are tall columnar cells with oval nucleus. Contain microvilli and function to absorb nutrients and secrete enzymes.

26
Q

What are goblet cells?

A

They are cells that are interspersed between enterocytes. They increase in number down the tract. They produce mucins.

27
Q

What are Paneth cells?

A

They are cells located in base of crypts. They contain lysozyme which has antibacterial activity.

28
Q

What are duodenal glands?

A

They are a part of MALT and are situated in the lamina propria of the small intestine.

29
Q

What are the two types of small intestine motility?

A
  1. Segmentation – it is a ring-like contraction and relaxation of muscularis that causes mixing and is controlled by pacemaker cells.
  2. Migrating motility complex – propagating contractions propel chyme forward and is controlled by hormones.
30
Q

What are the two types of intestine motility in the large intestine?

A
  1. Non-propulsive – main motility, pacemaker cells, segmental and slow
  2. Propulsive – mass movement, moves real fast, controlled by hormones
31
Q

What are the GIT accessory organs?

A
  1. Salivary glands
  2. Liver
  3. Gallbladder
  4. Pancrease
32
Q

What is the gallbladder

A

It is a hollow pear-shaped organ; divided into 3 regions fundus, body and neck. It is located in the fossa in posterior surface of liver’s right lobe, Has a cystic duct that extends to union with hepatic duct forming the common bile duct. Than joins the pancreatic duct and releases pancreatic juice into the duodenum.

33
Q

What is the main function of gallbladder?

A

Main function is bile storage – because bile is constantly produced by the liver, but during meals the bile can not be used to close of hepatopancreatic sphincter, thus gallbladder is need to store the up low of bile.
It also modifies the bile by absorbing water and concentrating the salts. This could cause the gallstones.

34
Q

What are the way by which bile secretion is regulated?

A
  1. Neural: Vagal stimulation causes increased liver bile flow and gallbladder contraction.
  2. Hormonal: Secretin (produced by the duodenum)
  3. Cholecystokinin which is part of hormone release
  4. Chemical: Bile salts also stimulate bile secretion
35
Q

How does bile facilitate digestion?

A

With bile salts:

  1. Process of emulsification – triglycerides are insoluble thus aggregate like lipid droplets – bile salts embed themselves within droplets as they are amphipathic – this cause a creation of shell meaning that the triglyceride droplets are broken down and could be broken down by pancreatic lipase.
  2. Formation of micelles – after the breakdown the digestion products (free fatty acid, vitamin, cholesterol) are put into micelles through use of bile salts – this creates an easier site of absorption (enterocytes).
36
Q

What is the histological structure of the gallbladder?

A

It has a simple columnar epithelium with an underlying lamina propria and muscularis with all direction fibers. Has serosa and adventitia.
The lining of the gallbladder has lining epithelial cells which are specialized for water uptake – they have abundant microvilli and prominent mitochondria. Highly dependent on sodium transport.

37
Q

What are the two functions of the pancreas?

A
  1. Endocrine function – pancreatic islets – produce insulin, glucagon and somatostatin - pale
  2. Exocrine function – groups acinini grape like clusters – form lobules separated by septa – majority of the pancrease – composed of serous cells containing zymogen granules
38
Q

What are the 4 duct systems in the pancreas?

A

Intercalated duct – intralobular – interlobular – main pancreatic duct.

39
Q

What do acini produce?

A

Bicarbonate ions & digestive enzymes. Some enzymes become activated as they arrive at the small intestine to not damage the pancrease.

40
Q

What caused the pancreatic secretion?

A

2 hormones – secretin and cholecystokinin

  1. CCK release is caused by presence of triglycerides in the duodenum
  2. Secretin release is caused by acid presence in the duodenum
41
Q

What are the 3 cells in the islet of Langerhans which are important?

A
  1. Beta cells – insulin production – anabolic hormone that lower blood glucose levels by promoting cellular uptake – increase after ingesting a meal
  2. Alpha cells – glucagon production – catabolic hormone that increase blood sugar by mobilizing energy-rich molecules from their stores
  3. D cell – somatostatin production
42
Q

What are the special senses?

A
  1. Smell
  2. Taste
  3. Sight
  4. Hear
  5. Maintain equilibrium & balance
43
Q

Why is smell and taste important?

A

Both olfaction and gustation rely on interaction of molecules with receptor cells wich generator neural signals that project to cerebral cortex & limbic system.

44
Q

What are five primary taste sensations?

A
  1. Salty (sodium)
  2. Sweet (glucose and alcohols)
  3. Sour (hydrogen ions – acid)
  4. Bitter (alkaloids)
  5. Umami (L-glutamate)
45
Q

What are the four important nerves for taste?

A
  1. Vagus nerve
  2. Glossopharyngeal nerve
  3. Facial nerve
46
Q

What are the four types of papillae?

A
  1. Vallate – taste buds on the lateral surface
  2. Fungiform (mushroom) – taste buds on the apical surface
  3. Foliate (leaf shape) – taste buds on the lateral surface
  4. Filiform – does not contain taste buds
47
Q

What are the three cells of the taste buds?

A
  1. Gustatory – receptors cells
  2. Supporting – basic support role
  3. Basal cells – develop into new receptor cells
48
Q

What is the mechanism of taste?

A
  1. Tastant binds to gustatory receptor cell
  2. Causes a depolarizing receptor potential (calcium entry)
  3. Neurotransmitter release from the receptor cell
  4. Detected by afferent nerve fibers that synapse with receptor cell
  5. Initiates action potential in terminal endings
49
Q

What are the two conditions which need to be met for substance to be smelled?

A
  1. It needs to be volatile
  2. It needs to be water soluble to dissolve in the mucosa
50
Q

What is the location of the olfactory epithelium?

A

The top of the nasal cavity.

51
Q

What are the three types of cells that are located in the olfactory epithelium?

A
  1. Olfactory cells
  2. Supporting cells
  3. Basal cells
52
Q

What are the olfactory membrane cells?

A

They are bipolar neurons with cilia. The cilia are long & nonmotile and used to increase the surface area in order to better respond to odoriferous substances by generating a receptor potential.

53
Q

How are olfactory cells used to transfer information to the olfactory and orbitofrontal cortex?

A
  1. The cilia on the olfactory cells recognizes and help to bind the odorant molecule
  2. The signal is generated
  3. Signal travels through the olfactory receptor to the olfactory bulb
  4. In the bulb, olfactory receptors bind with different mitral cells
  5. Mitra cells carry the signal to the olfactory and orbitofrontal cortex
54
Q

What is the role of supporting cells in the olfactory epithelium?

A

Basically support. They are free surface containing microvilli and are binded to the olfactory cells. They also contain a light-yellow pigment, lipofucin.

55
Q

What is the role of basal cells in the olfactory epithelium?

A

They act as stem cells and continually undergo division to replace receptors.

56
Q

What is the role of olfactory glands in the olfactory epithelium?

A

To produce mucus which moistens surface & dissolves odorants so that transduction can occur.

57
Q

What are the three key regions involved with swallowing?

A
  1. Mouth – buccal phase – food is passed into the oropharynx voluntarily
  2. Pharynx – pharyngeal phase – involuntary boulus passed from the pharynx into the oesophagus
  3. Oesophagus – oesophageal phase – involuntary passage of bolus through the oesophagus into the stomach
58
Q

What are the 4 steps of buccal stage?

A
  1. Compression of the bolus against hard palate
  2. Retraction of the tongue forces bolus into the oropharynx
  3. Elevation of the soft palate seals off the oropharynx
  4. Once bolus enters the oropharynx, reflex response are initiated and the bolus is moved towards the stomach
59
Q

What are the 4 steps of pharyngeal stage?

A
  1. Tactile receptors on palatal arches & uvula are stimulated
  2. Pattern of muscle contraction in the pharyngeal muscles is triggered by th swallowing center in the medulla
  3. Elevation of the larynx & folding of the epiglottis results from contractions of the pharyngeal muscles
  4. Pharyngeal constrictors then force the bolus thru the pharynx, past closed glottis and into oesophagus

Dentistry BDS1 Sem 2 (14 decks)

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