Digestive System Flashcards
(94 cards)
1
Q
What are functions of the gastrointestinal system?
A
- prehension: ingestion followed by fragmentation
- mechanical + enzymatic breakdown (fermentation) of nutrients: digestion
- absorption of nutrients
- synthesis/secretion (hormones)
- excretion of waste
2
Q
What are differences between the stomach/colon of equines, ruminants, and canines?
A
- equine: large cecum
- bovine: 4-chambered stomach
- canine: “normal’
3
Q
What features of the digestive system are endoderm derived? Mesoderm? Ectoderm?
A
- endoderm-derived: epithelium (mucosa), parenchymatous organs (ex: liver + pancreas) and associated glands
- mesoderm-derived: submucosa, muscle layers, serosa, mesentery
- ectoderm-derived: stratified squamous epithelium (oral cavity + anus) and nerve plexi
4
Q
What is the lining epithelium of the lips to the non-glandular stomach? The glandular stomach and intestine? The anus?
A
- stratified squamous epithelium
- simple columnar epithelium
- also stratified squamous!
5
Q
What are some features of the oral cavity?
A
- formed by: lips, cheeks, palate, pharynx, and tongue
- mucosa lined by: stratified squamous epithelium (keratinized or not)
- submucosa of connective tissue
- salivary glands and tonsils
- ruminants have a dental pad
6
Q
What are some features of the tongue?
A
- covered by mucosa: stratified squamous epithelium, keratinized on dorsal surface
- papillae (mechanical + gustatory) on dorsal surface
- some have taste buds
- skeletal muscle arranged longitudinally, transversely, and vertically (think of tongue motion)
7
Q
What are some factors that influence dentition?
A
- type of food consumed
- prehension
- mastication
8
Q
What are some structures of teeth?
A
- hard structures:
- enamel: covers external surface above gum line
- cementum: covers external surface below gumline
- dentin: beneath enamel and cementum
- soft structures:
- pulp
- peridontal ligament
9
Q
What cells form the structures of teeth?
A
- hard structures:
- enamel: ameloblasts
- cementum: cementoblasts
- dentin: odontoblasts
- soft structures:
- pulp: loose CT + nerves
- peridontal ligament: fibroblasts
10
Q
In what orientation do enamel and dentin form during tooth development?
A
- odontoblasts cover the surface of the mesenchymal papilla and produce dentin
- ameloblasts are tall columnar cells that produce enamel
- enamel forms more distal to dentin
11
Q
What are the two kinds of teeth, in reference to height?
A
- brachydont (low crowned) + hypsodont (high crowned)
12
Q
What are features of brachydont dentition?
A
- short + cease to grow after eruption
- crown (above gingiva), neck (restricted region below gingiva)
- one or more roots embedded in a boney socket (alveolus)
- all teeth of carnivores, incisors of ruminants, teeth of pigs (- incisors)
13
Q
What are features of hypsodont dentition?
A
- tall and continue to grow after eruption
- no crown and neck (elongated body)
- horses, cheek teeth of ruminants, canine teeth of pigs
14
Q
What is the general organization of tubular digestive organs?
A
- muscular tube with 4 tunics:
- mucosa
- inner epithelium
- middle lamina propria
- thin outer muscularis mucosae
- submucosa
- muscularis
- inner circular
- outer longitudinal
- serosa
- (adventitia if abuts other structures)
- mucosa
15
Q
What are features of the mucosa?
A
- epithelial lining
- simple columnar + glandular
- lamina propria
- loose connective tissue
- blood vessels, lymphatics, lymphocytes, smooth muscle cells
- supports epithelium
- muscularis mucosae
- always SMOOTH muscle
16
Q
What are features of the submucosa?
A
- loose connective tissue (looser than in lamina propria)
- facilitates MOTILITY of the mucosa
- contains vessels, a nerve plexus (submucosa plexus), +/- lymphatic nodules, glands
- P = papilla
- MM = muscularis mucosa
- MP = muscularis
- SM = submucosa
- M = mucosa
17
Q
What are features of the muscularis?
A
- may be smooth or skeletal muscle
- usually 2 layers of smooth muscle: inner circular + outer longitudinal
- controls lumen size, motility of tube
- contains myenteric nerve plexus and vessels
18
Q
What are features of the enteric nervous system?
A
- division of autonomic nervous system
- 2 distinct regions:
- submucosal plexus: meissner’s plexus
- myenteric plexus: auerbach’s plexus
- each region is a net of nerves connecting ganglia
19
Q
What are differences between the external coverings, serosa and adventitia?
A
- serosa: MESOTHELIUM + loose connective tissue +/- adipose tissue
- adventitia: loose/dense connective tissue only
20
Q
What is this feature of the digestive system?
- What kind of lining?
- What type of muscle?
- What type of external covering?
A
- esophagus
- stratified squamous
- skeletal + smooth
- adventitia
21
Q
What are some features of the esophagus?
A
- lined by non-keratinized or keratinized stratified squamous epithelium
- submucosa contains mucous glands
- muscularis may be composed of skeletal muscle only, or a mix of skeletal/smooth
- adventitia over most
- SS: non-keratinized stratified squamous epithelium
- LP: lamina propria
- MM: muscularis mucosae (SM)
- GL: submucosal glands will empty via ducts (D)
22
Q
What kinds of muscle surround the esophagus comparatively across species?
A
23
Q
What type of lining is in the stomach? What type of muscle? What type of external covering?
A
- simple columnar/glandular
- smooth
- serosa
24
Q
What are features of the stomach?
A
- distinction of digestive tube with sphincters at entry (cardia) and at exit (pyloris)
- mucosa may be non-glandular ( stratified squamous) or glandular (simple columnar epithelium)
25
What are the types of stomach structures?
- simple
- compound mutichambered
- composite
26
What are the species-specific differences in stomach structures?
27
T/F: equines have a simple stomach, with a feature called margo plicatus
- false; composite stomach
28
What are the components of a ruminant compound multi-chambered stomach? Which parts are forestomach vs “true”stomach?
- forestomach
- rumen
- reticulum
- omasum
- true stomach
- abomasum
29
What feature of the ruminant stomach is this? What are some features?
- rumen
- largest chamber of the forestomach
- low papillae
- increased surface area enhances passive absorption of VOLATILE FATTY ACIDS
- lined by keratinized squamous epithelium
30
What feature of the ruminant stomach is this? What are some features?
- reticulum
- honeycomb pattern
- small segments of smooth muscle along ridges
- lined by keratinized squamous epithelium
31
What feature of the ruminant stomach is this?
- omasum
- lined by keratinized squamous epithelium
32
What are the functions of the ruminant forestomach?
- rumen + reticulum
- mixing, eructation, regurgitation, movement of ingesta, absorption of VFAs
- omasum
- squeezes ingesta, liquifies and moves it to the abomasum for further ingestion
33
What is the flow of digesta through a ruminant stomach?
- rum road
34
What is the abomasum?
- glandular “true” stomach of ruminants
35
What are the three stomach glandular regions?
- cardia
- fundus/body
- pylorus
36
What are some features of the glandular stomach?
- simple columnar mucous cells line surface of glandular mucosa in all 3 regions
- gastric pits: invaginations of lining epithelium leading to glands
- rugae (folds): allow distinction
- muscularis: consists of 3 layers of smooth muscle (oblique, circular, longitudinal)
- outer serosa
37
What are features of the glandular regions of the stomach?
- cardiac region: composed mainly of mucous glands
- fundic region: with proper gastric glands
- composed of:
- parietal cells (secrete HCl)
- chief cells (produce pepsinogen)
- endocrine G cell produce the GI hormone gastrin (enters blood stream)
- pyloric region: mucus glands and endocrine G cells
- ** all regions covered by surface mucous cells**
38
What region of the stomach is this? What are some features?
- cardiac region
39
What region of the stomach is this? What are some features?
- fundic region
- parietal cells: eosinophilic, central nucleus
- chief cells: basophilic, peripheral nucleus
40
What region of the stomach is this? What are some features?
- pyloric region
- mucous glands and endocrine G cells produce the GI hormone gastrin (enters bloodstream)
- ** G cells not visible without special stains
41
What type of lining is in intestines? Muscle? External covering?
- simple columnar/glandular
- smooth only
- serosa (mostly)
42
What are the splits of the intestines?
43
What are some features of small intestines?
- lined by simple columnar epithelium (enterocytes and goblet cells)
- enterocytes are absorptive
- goblet cells make mucus
- has circular folds, villi and microvilli to increase surface area
- submucosal glands located in duodenum (Brunner’s glands)
- lymphatic nodules in distal small intestine (Peyer’s patches)
44
What is this feature? What part of the digestive system is it found in?
- villi
- small intestine
45
What are some features of intestinal villi?
- villi
- confined to the small intestine
- papillary projections into lumen
- site of absorption
- intestinal crypts
- at the base of the villi
- invaginations of lining epithelium
- site of production/division
46
What are features of intestinal epithelium?
- enterocytes (absorptive cells with microvilli)
- goblet cells (mucus)
- stem cells
- enteroendocrine cells
47
What is indicated in this image? What part of the intestine system are they present in?
- crypts of lieberkuhn
- small intestines
48
Label the features of this longitudinal section of a villus
49
What are features of lamina propria of villi?
- microvasculature, lymphatics, and muscle in villi
50
What are lacteals? Some features?
- blind-ended lymphatic vessels in intestinal villi
- the chyle (lymph) found in lacteals is filtered through intestinal lymph nodes before ultimately reentering the blood at the jugular veins
51
T/F: there are few lymphocytes and plasma cells throughout the lamina propria
- false; vast numbers
52
What are the structures indicated ? What are some features?
- peyer’s patches
- aggregations of lymphoid nodules present in the lamina propria and submucosa of the small intestine
- seen in distal jejunum and ileum, but varies according to species
53
What are M cells?
- specialized epithelial cells that sample antigens from the luminal environment
- APC: antigen presenting cells
54
What gland produces alkaline mucus to protect the duodenum from acidic chyme?
- Brunner’s glands
- not present in non-mammalian species
55
What is the function of the large intestine?
- absorb H2O and secrete mucus in all species; fermentation and volatile fatty acid absorption in hind gut fermenters
56
What part of the digestive system is this? Label A/B. What are some features?
- large intestine (of a horse)
- A: taenia coli, B: haustra
- no villi
- intestinal crypts (glands) present as in small intestine,but relatively long
- lined by simple columnar epithelium (mostly goblet cells)
- pigs and horses have longitudinal flat bands called taenia coli,composed of smooth muscle an elastic fibers - form haustra
57
How can one distinguish different parts of the intestine? **
- small intestine: both villi + intestinal crypts
- duodenum: Brunner’s glands in mucosa
- jejunum: there are no specific structures in connective tissue of submucosa
- ileum: peyer’s patches (groups of lymphatic nodules)in submucosa
- large intestine: no villi, surface is smooth, only intestinal glands are present
58
What are some features of the rectum + anus?
- rectum: lined by simple columnar epithelium, stores feces, secretes mucus
- anus: lined by stratified squamous epithelium
- in the pelvic cavity
59
What are the glandular regions of the anus?
- anal glands: empty into the lumen of the anus
- anal sac glands: empty into anal sacs (carnivores)
- circumanal glands (dogs): nonpatent ducts; unknown function, can form benign tumors
60
T/F: there is a single anal sac gland above the anus in carnivores
- false; paired, below the anus
61
What is the green arrow indicating? What are some features?
- anal sac (in the recto-anal junction)
- lined by keratinized stratified squamous epithelium
- located between smooth muscle of the internal anal sphincter and the skeletal muscle of the external anal sphincter
- the glands of the anal sacs are:
- dog: tubular apocrine sweat glands
- cat: both sebaceous and tubular apocrine sweat glands
62
What structure is indicated? What are some features?
- circumanal/perianal glands
- present n the subcutis around the anus in dogs (also in skin near the prepuce, tail, flank, and groin)
- glands resemble hepatocytes, thus the name hepatoid glands
63
What part of the digestive tract is this? What features prove this?
- esophagus
- stratified squamous epithelium
- glands
64
What part of the digestive tract is this? What features prove this? What is labeled as 6?
- tongue
- muscle layers in 3 directions
- stratified squamous epithelium
- 6: taste buds
65
What part of the digestive tract is this? What features prove this?
- colon
- no intestinal villi or glands
- lots of crypt cells
66
What part of the digestive tract is this? What features prove this?
- stomach
- chief and parietal cells
- glands
67
What is saliva? What does it contain? What are its functions?
- liquid secreted by salivary glands
- contains: water, salts, mucin, enzymes (amylase, maltase, lipase), IgA, lysozyme, lactoferrin, and suspended cells (desquamated epithelial cells, leukocytes, bacteria)
- function: digestion, provide moisture and lubrication, local immunity, evaporative cooling
68
What are the divisions of salivary glands? What kinds of secretion?
- divided into major and minor glands:
- major salivary glands: parotid, sublingual, mandibular
- minor salivary glands are intramural: lingual, palatal, labial, buccal, zygomatic (carnivores), molar (cats)
- types of secretion: serous, mucous, mixed
69
What is the structure of salivary glands?
70
T/F: salivary glands are lobulated
- true
71
What kind of salivary gland is this? What kind of secretion does it have?
- parotid salivary gland
- serous
72
What kind of salivary gland is this? What kind of secretion is from structure A? structure B?
- sublingual salivary gland
- A: mucous
- B: serous
73
What are some features of the liver?
- largest visceral organ in the body, 1-4% of BW
- situated in the abdominal cavity caudal to the diaphragm
- strategic position in blood circulation
- 1/3 blood from hepatic artery
- 2/3 blood from portal vein
- ~25% of weight of liver is blood
74
What are some components of the liver?
- hepatocytes
- vasculature
- biliary trees
- kupffer cells (macrophage)
- ito/stellate cells
- oval/stem cells
- pit cells
- connective tissue
75
What feature of the digestive system is this?
- liver
76
What are hepatocytes?
- polygonal, epithelial liver cells
- workhorses:
- detoxification
- deamination (aa —> urea)
- produce bile
- produce various blood proteins
- gluconeogenesis
- store energy (glycogen and triglycerides)
- arrange in cords or plates
77
What is this image a example of? What are some features?
- vasculature in the liver
- portal triad: hepatic artery (HA), bile duct (BD), portal vein (PV) and several lymphatic vessels (LV)
- surrounded by collagenous extracellular matrix that forms an abrupt border with a circumferential row of hepatocytes aka the inviting plate (LP-dotted line)
78
T/F: blood and bile flow in the same direction from the portal field to the central vein
- false; blood flows from the portal field to the central vein, bile flows towards the portal field after production
79
What is the site of exchange between blood and hepatocytes?
- perisinusoidal space (space of disse)
80
What are features of the intrahepatic biliary tree?
- canaliculi: potential spaces
- canals and ductules lined by cuboidal epithelium (cholangiocytes)
- bile ductules located in the portal triads
81
What is shown in the image? Label the terms
- vasculature of the liver
82
What structure is shown here?
- intrahepatic biliary tree
83
What are features of kupffer cells?
- resident phagocytes of liver
- located within the blood sinusoids
- remove aged blood cells (may have intracellular iron pigment: hemosiderin, pathogens, some toxins
84
What feature of the liver is indicted here? What are some features?
- ito cells (stellate cells)
- vitamin a metabolism
- collagen production
- large round lipid vacuoles
- in space of disse
85
What are oval cells? Pit cells?
- oval cells
- pluripotent cells
- found in biliary tree
- pit cells
- resident granular leukocytes
- found in sinusoids
86
What is shown in this image? Be specific. What are some features?
- liver (pig)
- each lobe is covered by mesothelium (serosa) located over a connective tissue layer, the capsule
- organized into lobules separated by variable amounts of connective tissue septa
87
What is the anatomical and functional arrangement of the liver?
88
Which zone is more susceptible to direct-acting toxins? Which of the acinar zones is most susceptible to hypoxia?
- zone 1 (periportal)
- hepatocytes closest to O2 and nutrient rich arterial and portal inflow
- more susceptible to direct-acting toxins
- zone 3 (centrilobular)
- nearest venule - more susceptible to hypoxia
- detoxification enzymes: more susceptible to metabolites from toxins
89
What structure is shown in these images? What are some features?
- gallbladder
- accepts bile from cystic duct for storage
- abundant mucosal “folds” seen when gallbladder is empty
- bile ducts lined by short columnar epithelium
- gallbladder is lined by tall columnar epithelium
- epithelial cells capable of modifying bile (absorption of H2O and inorganic salts)
- muscularis of smooth muscle
- serosa surrounds almost the whole organ
90
What structure is shown in this image? What are some features?
- pancreas
- dual gland: exocrine and endocrine
- exocrine pancreas
- composed of tubuloacinar secretory units - produce digestive enzymes
- trypsinogen, chymotrypsinogen, lipase, amylase
- endocrine pancreas
- consists of pancreatic islets (islets of langerhans)
- produce hormones
- insulin, glucagon, somatostatin, pancreatic polypeptide
91
What is this structure? What are features of its structure?
- pancreas
92
What is this figure an example of?
- exocrine pancreas
- serous acinar glands
- product visible as zygotes granules
93
What is this structure? What are the features indicated?
- pancreas
- serous acinus (exocrine)
- islet of langerhans (endocrine)
- capillary
* eosinophilic zygote granules
94
What is this structure?
- pacinian corpuscle
