Digestion Part 1 intro-stomach

Question 1

What are the 5 stages of digestion?

Answer 1

The digestive system is the oragn system which processess food, extract nurit., eleiminate waste
1. Ingestion: intake food
2. digestion: mechanical and chemical breakdown of food into unesbale components
3. Absorbtion: uptake of usebale nuirtents into epithelia cells –> blood or lymph
4. Compaction: absobtion of water and consolidinating into feces
5. Defecation: eleimnation of feeces

Question 2

Two types of digestion

Answer 2

1. mechanical digestion: the physical breakdwon of food into smaller particles ( cutting and grinding of the teeth and by churning and pummeling from stomach and small intensine contractions)
2. Chemical Digestion: sereis of hydrolysis reactions that breakdown complex molcules into useable components ( digestuve enzymes made by salivary glands, stomach, small intestine)

Question 3

Digestive structures divisiosn

Answer 3

1. The Digestive Tract: Mouth–> pharynx–> esophagus–> stomach–> small inte–> large int–> anus
2. Acessory structures: Teeth, Tongue, Salivary Gland, Liver, Gallbladder, Pancreas ( not part of the contininous tube)

Question 4

Layers of the digestive tract

Answer 4

1. Mucosa (innermost)
   - Epithelium: straified squamos from mouth to epsophagus and lower anal canal –> Simiple Columnar (globelt cells)–> stratified squamos (anus)
   - Lamina Propia: loose areolar tissues
   - Muscularis interna/mucosa: smooth muscle
2. Submucosa ( Irregular connective tissue: glands , nerves, blood vess, nereve plexus, secreete mucus)
3. Muscularis Externa:
   - Innermost cirular muscle for peristalsis
   - outermost longitutional muscle for squeeze push
4. Serosa:
   - Areolar (thin)
   - Surronded by simiple squamos
   Can operate outside: plexuses isolate inflammation

Question 5

What are the mesenteries and omenta tissues?

Answer 5

1. Mesenteries help to prevent the digestive tract from twisting itself and provides clear passgeway for nerves and vessles, lymph nodes
   - Stomach and intestines suspended in mesenteries
   - Created from pariteal perotenum tuns inward toward mideline form posteior mesenetry
2. Omenta: fatty blanklets that cover the intestines:
   - Tow omenta in stomach
   - Greater omnetum hang from greater curvature and over small intes.
   - lesser omentum extends liver to lesser curvanture+ stomach.
   - Omenta adere to inflammed areas , immune cells, isolate infections that could cause periotnitis

Question 6

Mouth

Answer 6

• Oral and vacity functions in ingestion, taste, chemical digestion, smallowing, speech, respiration
• Lined with stratfied squamos epithelium that is kertanized for high absration (gums, cheek, hard palate)
• Cheeks and lips retain food , push back for chewing
• Frenulum: connections

Question 7

Tongue

Answer 7

• The tongue functions to manipulate food between teeth and is senistive
• Covered by non-kertanized stratified squamos epithelium
• projections called Linguinal Papillae (taste buds) functions to increase surface are for food contact and move bolus.
• Liguinal glands secrete part of salvia
  1. Filiform: no taste buds but touch
  2. Fungiform: mushroom like with tast buds
  3. Foliate Papillae: short vertical folds and present on each side of the tongue
  4. Circumvallate Papillae: dome shape structures that are where 1000s taste buds are

Question 8

What are parts of palate?

Answer 8

• Palate sepreates nasa cavity from oral cavity and has two structures.
  1. Hard palate is supported by ant. maxilla and palatine. (Tranverse ridges callled palatine ruage )
  3. Soft palate is muscular and spongey- the uvula retains food until ready to swallow

Question 9

Stucture of teeth

Answer 9

• teeth serve to mechanically, break food into smaller pieces and aid in swallowing and increase surface area for digest. enzymes to react. 32 adult teeth , 20 deciduous teeth replaced by 32 adult teeth
• Tooth sits in the alveolus socket: the alveolus is lined by the periodontal ligament ( keep connected)
• Crown above the gum and root below

Question 10

Malocclusion and Impacted

Answer 10

Impacted refers to tooth unable to grow in right angle while malocculsion is teeth not aligned.
- Osteopororsis can lead to tooth loss.

Question 11

Functions of Salvia and its components

Answer 11

1. Moisten and clean the mouth
2. Inhibit bacterial growth
3. Dissolve molecules for taste bud stimulation
4. digest straches and fats
5. Bind the bolus together and lubricate for swallowing

• Salvia is a hypotonic solution of 98% water and ph at 7 containing solutes, mucos, electrolytes, lysozyme, IgA, salivary amylase, lingual lipase

Question 12

Salivary Glands

Answer 12

1. Intrinsic Salivary Glands: are a number of small glands which reside in other oral tissues: They secrete salivia at a constant rate despite eating or not.
2. Extrinsic Salivary Glands: three pairs of larger , more discrete organs located outside the oral mucosa
   - Partotid Glands: located just beneath the skin antieor to earlobes ( mumps orgin) ( secretions enter through parotid duct).
   -** Submandibular glands**: located just haflway along mandible. Enters into mouth at papille under tongue
   - Subliingual glands: located in floor of mouth and have mutliple ducts that empty into stomach under the tongue behind submandibular papillae.

Question 13

Salivation

Answer 13

Extinsic salivary glands produce saliva due to food ingestion.
Parasympatheic stimuli: stimulate the glands to produce lots of salivai with enzymes.
Sympatheic: stimulate the glands to produce less salivia thick with mucos

Question 14

Structure of the pharynx

Answer 14

• Muscular Funnel that connects the esophagus and nasal cavity to the layrnx ( digestive meets respiriatory)
• Two layers:
  1) Deep layer of Longitudinal Muscle
  2) A superfical layer of circular muscle ( these are pharyngeal constictors which food is forced down during swallowing)

Question 15

Components of Pharynx

Answer 15

Divided into three regions
1. Nasopharynx: recieves the eustachain tubes from middle ear and contains pharyngeal tonsil ( destory pathogens). It is located above where food enters and is covered by the uveula during swallowing. Lined with pesudostratified columnar ( pasas air )
2. Oropharynx ( starts to become startfied squamos for protection) Space between the post. soft palate and epiglottis. As the nasophaynx bends into oropharynx the psedu. –> stratifed to protect from abrasion. Contains tonsils palatine and ligunial tonsils ( pass air/food)
3. Layrnngopharynx: posteior to laynx moving from epiglottis to the cricoid cartilage and to esophagus. Also lined with startfied sq. ( pass air and food)

Question 16

Epiglottis

Answer 16

• Folds over the trachea during swallowing ( force food into esophagus)

Question 17

The Esophagus

Answer 17

• Straight muscular tube where NO DIGESTION occurs only movement
• Compostion: Upper 1/3 is skeletal , middle 1/3 mixed, lower 1/3 smooth.
• Begins between C6 and critoid cartilage
• Moves through mediastinum and diaphram at esophageal hiatus.
• Joins the stomach at the cardiac sphincter ( lower esophageal spincter prevents stomach acid from entering the esophagos)
• Mucosa (outer) is composed of non-kertainized stratifed squamos.
• The submucosa contains eosphgeal glands that secrete mucus to lubircate in the lumen.

Question 18

The Esophagus Disorders: Prebyesophagus and Achalasia

Answer 18

Preby: motor action of esophagus is not coordinated with the cardiac or esophogeal sphincter and the sphincter may open causing regurgitation or heart burn.
Achalasia: cardiac sphincter may not open when bolus arrives. Food may remain for ours instead of seconds and cause megaesophagus. This may cause rupturing or death and can be cured through botox

Question 19

The swallowing or degulitition process

Answer 19

Complex action occurs in 22 muscles in mouth, pharynx, esophagus, coorindated via medulla
- Swallowing center communicates with phraynx, esophagus, carnial nereves through 5,7,9, and 12.
1. Buccal oral phase: is voluntary control
- The upper esophegeal sphincter is closed
- Tongue presses hard against the hard palate forcing bolus down oropharynx.
2. Pharyngeal-esophageal phase: involuntary control
- The tongue blocks the mouth
- Soft palate and ulvua rise closing off nasopharynx
- Larynx rises so that epiglottis covers trachea
- Upper esophageal sphincter contracts after bolus enters.
- Perislatsis moves down esophagus to stomach
- The gastrophageal sphincter (cardiac sphincter) opens allowing bolus to enter stomach then closes after. Contract close, relax open

Dysphagia: diffculty swallowing

Question 20

The Stomach

Answer 20

• Produces a soupy mixture of semi-digested food call chyme
• J-shaped organ with greater, lesser curvature
• regions of stomach include cardiac region, body, plyoric region ( the pyloric region leads to plyorus which is a narrow passage that leads to the duodenum through pyloric sphincter.
• Upper sphincter= cardiac sphincter
• ## Pyloric region–> pyloric sphincter: sepreates stomtach from dudeonum

Question 21

Innervation and Cicculation

Answer 21

• Stomach is innervated by the parasympatheic fibers from the vagus nereve and sympatheic fibers from celiac ganglia.
• Gastric arteries branch to form celiac trunk.

Question 22

Stomach Microscopic Structures

Answer 22

• The mucosa is covered by simiple columnar epithelium to hold into the goblet cells that secrete mucous. This protects and ais in buffering stomach acid.
• Apical top cells have mucin which becomes mucos ( buffer )
• Longtiudinal ridges called gastric rugae
• Gastric pits
• Musclaris externa has an extra layer of oblique layer along with circular layer and longitudinal layers. Vital for punneling the bolus into chyme increase SA of stomach

Question 23

What are the gastric gland cell types?

Answer 23

1. Mucous Cells: secrete mucus and found predominatly in the cardiac and pyloric glands
2. Parietal cells: Parietal = wall secrete hydrochloric acid and instrinsic factor as well as gherlin. Walls of glands
3. G-Cells: Secrete gastrin and are found in pyloric glands
4. Stem cells: divide rapidly to produce new cells to replace dying ones
5. Chief cells: secrete gastric lipase (useless) and pepisogen which
6. Enterendocrine cells: secrete hormones and pacacrine messangers that regulate digestion.

Question 24

What is a Zymogen and Pepsinogen?

Answer 24

1. DEFN Zymogen: inactive protein which is converted into active form through removal of amino acids ( refer to the inactive proteins that get secreted in inactive form)
   Example: Pepsinogen: is the zymogen which when it comes into contact with HCI removes some amino aicds becoming pepsin (active) Pepsin digests proteins
   Inactive form allows for protection

Question 25

What is the gastric secetion of hydrochloric acid?

Answer 25

• Gastric Glnads produce 3 L a day
• Gastric Juice is water, HCI, pepsin
  G-Cells secrete gastrin which in turn stimulates the parietal cells to make HCI

Question 26

Function of stomach acid:

Answer 26

1. Activiates pepsin and ligunal lipase
2. Breaks up connective tissue and plant cell wall
3. Converts ingested Ferric Ions to ferrosu Ions
4. Non specific dieseases resistance

Question 27

What is intrinsic factor

Answer 27

• It is a glycoprotein that is vital in absorbing vit B12
  Vit B12 is needed to make EMF which is key in making Red blood cells.
• With atropy of pairtal cells, less intrinsc factor is secreted and causes decrease in erthoryctes (pernicious anemia)

Question 28

Gastric Secretions of Chemical Messangers CCK and Secretin

Answer 28

1. Cholecystokini CCK: stimulates the release of bile into intestine and the secretion of enzymes by pancreas ( stimulates fat and protein digestion) Increase pancreas secretions and increase gallbladder contractions.
2. Secretin: * Regulates water balance and secretiosn from pancreas, liver, stomach. More specfic: secretin will stimulate the pancrease to secrete more bicarbonate which helps buffer acid and raise pH**

3. Sub. P ( vomit, pain)
4. VIP ( increase gut motility)
5. GIP ( induce insultin)
6. NPY ( appeite stimulate)

Question 29

How does the stomach protect itself?

Answer 29

1. Mucous coat: thick alakaine mucus provide buffer for acid
2. Tight Junctions: epithelia cells joined via gap junctions prevent acid leak
3. Epiethlium cell replacement: rapid cell replacement of epthelim lining

Question 30

Gastric Secretion Regulation

Answer 30

Three stages, stages are dependent on stomach, controlled by brain, small intestine. Can occur at same time
1. Cephalic phase: hypothalmus–> medullaa oblongata–> vagus nerve
2. Gastric phase: 2/3 of gastric secretion: increase pH, increase strench which activates –> vagovagal reflex and myenteric reflex –> ( three chemicals stimulate gastric secretion and they all stimulate the parietal cells to produce hydrocholric acid and intrinsic factor:
- Acetycholine ( stimulate G cells to secret gastrin and ach stimulate mucos )
- Hismatine same as ach.
- Gastrin ( stimulate parietal cells to secrete HCI and chief cells to produce pepsinogen)
3. Interstial Phase: lower pH and high amounts of lipids
- Enterogastric reflex is triggered which stimulates CCK and secretin

Question 31

Cephalic Phase

Answer 31

• Occur before food enters stomach
• Trigger act via vagus nereve to stimulate gastric glands to prepare
  Hypothalmus–> medulla oblogata–> vagus nerve

Question 32

Gastric Phase

Answer 32

• Once food enters stomach local hormone initae phase
  2/3 of gastric secretion: increase pH, increase strench which activates –> vasovagal reflex and myenteric reflex. –> ( three chemicals stimulate gastric secretion and they all stimulate the parietal cells to produce hydrocholric acid and intrinsic factor:
• Acetycholine ( stimulate G cells to secret gastrin and ach stimulate mucos )
• Hismatine same as ach.
• Gastrin ( stimulate parietal cells to secrete HCI and chief cells to produce pepsinogen)

Question 33

Interstial Phase

Answer 33

• Begins with brief stimulatory component followed by inhibition
• Interstial Phase: lower pH and high amounts of lipids
• Enterogastric reflex is triggered which stimulates CCK and secretin
• The duodenum responds to chyme and modifes output through hormones: initially increases gastric but inhbits after
• The acid and semi digested fats in the duodenum trigger the enterogastric reflex.

Question 34

Intestinal Phase CCK and Secretin

Answer 34

1. CCK and secretin are secreted via enteronenodcrine cells ( CCK release is stim via protein and fats in chyme) (Secretin simulated by acidic chyme)
2. Pancretic Secretion: CCk induce secretion by acinar cells of pancreatic juice. Secretin causes secretion by duct cells of HCO3
   - Vagus nerve weakly stimulates during cephalic and gastric phases
3. Bile Secretion by Liver
4. Gallbladder Contraction
5. Hepatonpancretic sphincter releaxes