The Digestive System Flashcards
1
Q
Organs of the Alimentary Canal:
A
- Consist of the oral cavity, oropharynx, laryngopharynx, the esophagus, the stomach; the small intestine which consist of (duodenum, jejunum and ileum) and large intestine (transverse colon, descending colon, ascending colon, cecum, sigmoid colon, Rectum, Appendix, Anal Canal
- Alimentary Canal = One big tube from our mouth to anus
- Accessory Digestive Organs: tounge teeth, salivary glands in the oral cavity, pancreas, gallbladder, liver feed into the small intestines
2
Q
A
- Pertitoneum and will sit within Pertitoneal Cavity
- like the serous membranes that we have surrounding the heart, the percardium and surround the lungs, the pleural membrane both of them are serous membranes so we’ll have a visceral and parietal piece it’s all one piece where the parietal piece is against the body wall. And Visceral piece is wrapped around the individual organs
- peritoneal fluid - creating a slippery friction surface
3
Q
The Mesentery
A
- Mesentery: Two layers of fused peritoneum
- Ventral Mesentery - attaches to the posterior anterior abdominal wall
- Falciform Ligament - separates the right and left lobe of the liver
- Lesser Omentum - runs on the underside of liver down to the lesser curvature of the stomach (contains fat, bloodvessels, nerves and macrophages)
- Dorsal Mesentery - attaches to the posterior abdominal wall
- Greater Omentum - attaches from the greater curvature of the stomach and hangs down to the rest of the intestine
- Transverse mesocolon - attach to transverse colon (runs horizontally) of large intestine to the posterior wall
- Sigmoid Mesocolon - attach to the S shape part of the large intestine to the posterior abdominal wall
- Carrying bloodvessels and nerves to where they need to go
- lots of pockets of macrophages, they serve as immune surveillance and can quickly wall off any sort of infection
4
Q
Side view of Mesentary
A
5
Q
Some organs are retroperitoneal
A
- Some organs are retroperitoneal
- located behind the peritoneal cavity
- The peritoneal cavity within the abdomen, a smaller cavity within the abdominal cavity
- We have kidneys, adrenal glands which sit on top of the kidneys
- Arorta and inferior vena cava, duodenum (first part of the small intestine, ascending colon (bc it’s on the right side)
6
Q
Control of Digestion
A
- 4 Layers
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Mucosa
- Epithelium - interestines - we have a simple layer to aid with diffusion and movement of molecules through into the blood stream where as our esophagus and pharynx stratified squamous epithelium bc of the friction forces
- move to the stomach - simple columnar
- end of our anus - stratifed squamous
- Lamina propria - cross betwn loose aerolar connective tissue and dense irregular connective tissue. Epithelium and connective tissue put those together Muscosa.
- malt tissue (repositiories of white blood cells/helps protect us)
- fats move through the lymphatic system
- Globet cells to allow easy passage/digestive passive as it moves there
- Muscularis mucosa - thin layer of thin smooth muscle cells - flicking food away from walls
- Submucosa - mixed btwn loose aerolar and dense irregular - most of the main blood vessels and main lymphatics. tissue the smaller blood vessels, more of the capillaries been found here in this lamina propria surrounding the mucosa and then join up with larger blood vessels and nerves in the submucosa
-
Muscularis Externa - main smooth muscle we see in our digestive organs
- Circular layer - inner most layer
- longitudinal - running with the direction of the organ
-
Serosa - same as visceral peritoneum - would be our peritoneum - outer most layer
- Serous membrane
- Found in esophagus Adventitia - outermost layer non slippery bc there no serous peritoneal fluid
-
Mucosa
7
Q
A
- Smooth muscle is involuntary and no striations, long a cylinderial
- actin and myosin attached to intermediate fillaments
- No mitochondria
2 types of contraction
- Peristalsis - longitudinal (over layer) movement of particles our digestive tract
- like squeezing a toothpaste - peristalsistic waves carry the food down
- Circular inner most layer Segmentation - mixing - squeezing the middle of a tube to ensure food particles run across the mucosa and attract the nutrients
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8
Q
The Enteric Nervous System
A
- The entire nervous system within the gut
- Neurons located in gut walls
- Myenteric nerve plexus - a plexus of that nerves that’s right along the border of all the smooth muscle
- Submucosal nerve plexus - deeper into the submucosa to send more signals, for ex, the mucosal glands that muscularis, mucosae causing it to contract occasionally
- Most of the smooth muscle here communicate through gap junctions
- just need one branch to signal to contract and calcium coming in to stem that contraction but then all those ions that are coming will also be able to pass along the way to other nearby smooth muscle and trigger wider more localized contraction
9
Q
Clinical Correlate: Hirschspring’s Disease
A
- a developmental abnormality where the enteric nervous system fails to form properly
- the neurons the myenteric and submucosal plexuses they fail to migrate to the last part of the large intestines, rectum and stigmoid colon
- What process will there not occur properly?
- Peristalisis
- So we’ll digest food which will move through the alimentary canal, move through the colon all the way around and then it’s gonna get stuck to the last part
- Can be chronically constipated
- identified in infants
- Treamentt is surgical - can be an ostomy or “pull-through” procedure
10
Q
A
- What kind of epithelium is located in the pharync?
- stratifed squamous epithelium - friction force
- Nasal pharynx - pseudostratifed columnar epithelium w/ cilia
- Hard palate - made of maxilla and palatine bone at the posterior aspect
- Soft palate - helps you gag - will extend and become your uvula that can flip up & seal off your nasopharynx and prevent different foods from going into your nasal cavity
- Extrinsic muscle cause the tongue to move side to side
- Intrinsic muscle controls your tongue to the tongue
- The tongue and teeth take part of the digestive process
- Saliva that’s being released in the oral cavity also helping with digestion, enzymes within saliva like amylase that starts to break down carbohydrates, lipase that breaks down fats
- mechanical and chemical digestion that starts in oral cavity then will continue as we move down the alimentary canal
- Immune function - lysozymes that work to kill bacteria
- Oropharynx - back of the oral cavity
- Epiglottis - flips over the larynx to prevent food from going down larynx
- Hyoid bone
- Laryngopharynx
- Esophagus
- Lips help close our both
Which cranial nerve control the lips
- CN VII - the facial nerve responsible for all muscles of facial expression
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11
Q
A
- (bumps on the tongue)
- Filiform Papilla - keratinized just like our skin full of keratin their purpose is for gripping food, grip it and mash it up against the hard palate
- Fungiform Paillia (tip of tongue) and vallate papilla (larger form a V shape posterior of tongue) - have sensory receptors (taste buds)
Which cranial nerve controls the tongue?
- Cranial nerve XII - Hypoglossal nerve
Cranial nerves responsible for eating?
- CN VII - lips
- CN V -Jaw
- CN IX - help move food backwards in mouth
- CN X - Innervating larynx & pharynx to help w/ swallowing
- CN XII - moving the tongue
Lingual tonsils
- Immmune surveillance piece
- Some taste sensation in the posterior third of the tongue CN IX
12
Q
Salivary Glands
A
- Produced saliva: is mostly a seromucus fluid both watery and has mucal components within it that has different types of enzyme that can break down particles also lysozymes serve as a immune fuction to kill bacteria
- Intrinsic Salivary Glands - produced little bits of saliva to keep mucosa moist to prevent it drying out
-
Extrinsic Salivary Glands - participate with digestive for instance - we have parotid glands (controlled by CN IX - produces a water mucus enters through the second molar on roof on mouth) - located external, superficial to the masseter muscle they have a duct that travels through around the masseter to enter into the mouth
- Submandibular Gland - one on each side just medial to the angle of the mandible - water, little mucus-y
- Sublingual Gland - right beneath tongue - tend to produce saliva - thicker more mucus-y
13
Q
Esophagus
A
- Tube that connects our mouth to stomach
- First 1/3 = Skeletal muscle - voluntary control
- Middle 1/3 = mix of smooth and skeletal muscle
- Last 1/3 = smooth muscle
- Sphineters - contriction points
- Upper esophageal - air doesn’t go down the esophogus - most of the time when we’re not eating the esophogus is closed
- Lower esophageal - limitng movement of acid back up to the esophogus - simple columnar epithelium (soon as you get to stomach)
- Stratified squamous epithelium - all along the esophogus
It’s main job is to perform perstalsis - move food particles from the mouth to the stomach
14
Q
Gastroesophageal Reflux Disease (GERD)
A
- Aka acid reflux
- Affects 10-20% of the population
- 20% of cases can progress to Barett’s esophagus - striking pattern - the cells along here due to contact exposure due to stomach acid shift from stratified squamous epithelium to simple columnar epithelium high chance it can transtition to cancer
- 10% of barrett’s esophagus will transtition to cancer and 5 year survival rates for esophageal cancer are abysmal
- Food triggers - acidic drinks, advil, coffee - causes lower esophageal sphincter to relax a bit and that allows the acid to come back up
15
Q
The Stomach
A
- Simple Columnar Epithelium
- no absorption here but water, salt, alcohol - purpose further digestion
- Hydrochloric acid within the stomach
- Help denature proteins and break down molecules
- Produces lots of alkaline mucus to counteract the acid so when it interacts with the mucus it’ll be neutralized - all surfaces within here are covered with the akaline mucus
- Extra layer within Musclaris Externa
- Longitudinal layer
- Circular layer
- Oblique layer - churning within the stomach (only place that has this layer)
- Cardia first part of the stomach - close to heart
- Fundus - roof of the stomach
- Body
- Rugae - folds of the stomach
- if expanded the stomach can hold up to four liters of fluid
- Pyloric sphincter is true spincter, musular sphincter that limits what can go through into the small intestine
- Pyloyic canal - is the narrowing of the pylorus as it gets to this part
- Phyloric antrum - cave like area
- Duodenum - first part of small intestine where food at this point the mixture is called Chyme head from the stomach through the pyloric sphincter into the duodenum
Which artery is supplying the stomach?
Everything from the celiac trunck, ends up supplying different parts of the stomach
- left gastric artery going to supply stomach
- also have a branch from the splenic artery
- branch from common hepatic artery
16
Q
Gastric Pits
A
- Mucus Neck Cells - producing the alkaline mucus to coat the stomach
- Parietal cells - producing hydrochloric acid
- Cheif cells - produce an enzyme known pepsinogen
- when pepsinogen mixes with hydrochloric acid it will be covered to pepsin (job to break down/digestion of proteins)
- smaller peptides apart into amino acids that then be taken up by our cells
- Entroendocrine cells secrete a hormone gastrin - released when food particles are entering the stomach oftentimes as the PH of the stomach starts to elevate bc we eat things that are not super acidic and when gastin is released it will bind nearby to the parietal cells and the chief cells and cause them to release the hydrochloric acid and the pepsinogen
17
Q
A
- Chyme gets released into the small intestine to start extracting nutrients
- We have peristalitic waves via the longitudinal layer that will move this chyme towards the pyloric sphincter and if the first part of the duodenum is not open if it’s closed and it’s empty the wave of the peristalsis is going to cause the pyloric sphincter to open up and small amounts of chyme are going to move into the first part of the duodenum (30 milliliters of fluid) as soon as it fills the stretch of the area will reflexively close the pyloric sphincter sp that peristaltic waves are gonna sauce the chyme to come into a wall, a barrier, then move backwards then you get the continued churning.
- As we digestion this more of the chyme will get let through and makes sure we extract as many nutrients (moves slowely)
