Digestive System Flashcards
1
Q
What organs in digestive system do (5)
A
- Ingest food
- Transport ingested food
- Digest material into smaller usable components
- absorb necessary nutrients into bloodstream
- expel waste products from body
2
Q
2 Categories of Organs in digestive system
A
- Digestive Organs: make up gastrointestinal tract (aka digestive tract or alimentary canal)
- Accessory digestive organs: organs that aide in digestion
3
Q
Digestive system functions (6)
A
- Ingestion
- Digestion
- Propulsion
- secretion
- Absorption
- Elimination of wastes
4
Q
GI Tract Organs (6)
A
- Oral cavity
- Pharynx
- oesophagus
- stomach
- small intestine
- large intestine
5
Q
Cheeks, Lips & Palate
- palate (2 types)
- uvula
A
- Palate = roof of oral cavity
- anterior 2/3 = hard palate (comprised of bone)
- posterior 1/3 = soft palate (musclar)
- uvula extends from it -> elevates during swallowing and closes off posterior entrance to nasopharynx
6
Q
Cheeks, lips & palate
- Cheeks and lips
- labial fenulum
A
- Cheeks = lateral wall (mainly comprised of buccinator muscles)
- end anteriorly as lips - Gingivae (gums) cover alveolar processes of teeth
- internal surface of upper and lower lips attached to gingivae by thin, midline mucosa fold called labial frenulum.
7
Q
What comprises the oral cavity
A
- Cheeks, lips & palate
- Tongue
- salivary glands
- teeth
8
Q
Cheeks, Lips and Palate
- fauces
- 2 muscles that bind it laterally
- palatine tonsils -> where found
A
- Fauces represent opening from oral cavity to oropharynx
- are bounded laterally by paired muscular folds (palatoglossal arch & palatopharyngeal arch)
- Palatine tonsils housed between two arches
9
Q
Tongue
- What it does
- bolus
- lingual frenulum (what it is & where it attaches)
A
- Manipulates & mixes ingested materials during chewing & helps compress partially digested materials into bolus
- Bolus: globular mass of ingested materials that can be more easily swallowed
- inner surface of tongue attaches to floor of oral cavity by thin, midline mucous membrane called lingual frenulum
10
Q
Gustation
- what is it
- Gustatory cells (what are they called?)
- where located
A
- Sense of taste
- Gustatory cells = taste receptors housed in specialized organs called TASTE BUDS
- located on dorsal surface of tongue in elevated epithelial & CT called papillae
11
Q
Tongue Papillae (4 types)
A
- Filiform papillae
- Fungiform papillae
- Vallate papillae (form a V shape)
- Foliate papillae
12
Q
Salivary Glands
- role
- 5 functions
A
-produce & secrete saliva into oral cavity
FUNCTIONS;
-moistens ingested materials to become slick bolus
-Moistens, cleanses & lubricates struct. of oral cavity
-chem digestion of ingested materials
-antibacterial action
-dissolves materials so that taste receptors on tongue can be stimulated
13
Q
3 pairs of salivary glands -> where all are located
A
- located external to oral cavity
1. Parotid glands
2. Submandibular glands
3. Sublingual glands
14
Q
Salivary Glands; Parotid salivary glands
- where found
- how much saliva they produce
A
- longest of 3 salivary glands
- located anterior & inferior to ear
- secrete 25-30% total saliva
- run parallel to zygomatic arch & pierces buccinator muscle
- also secrete amylase
15
Q
Salivary glands; Submandibular glands
- where found
- how much saliva they produce
A
- reside inferior to body of mandible
- Produce majority of saliva (60-70%)
- submandibular duct transports saliva from each gland through papilla in floor of mouth
- on lateral sides of lingual frenulum
16
Q
Salivary glands; Sublingual salivary glands
- where found
- how much saliva they produce
A
- Inferior to tongue
- Each gland extends multiple tiny sublingual ducts that open onto inferior surface of oral cavity (posterior to submandibular duct papillae
- Only contribute 3-5% total saliva
17
Q
Salivary gland secretion (2 types)
A
-2 types of secretory cells found in glands;
- Mucous cells: secrete mucin, which forms mucus upon hydration (provides lubrication in oral cavity)
- Serous cells: secrete watery fluid containing ions, lysozyme and salivary amylase (involved in chemical digestion)
18
Q
Salivary glands and types of secretion
A
- Parotoid = serous secretion
- Submandibular = mucous and serous secretions
- Sublingual = mucous and serous secretions
19
Q
Teeth
- Parts of tooth
- dentin
- enamel
- centre of tooth
- root canal
A
- aka dentition
- Tooth has exposed crown, constricted neck & 1 or more roots that fit into dental alveoli
- dentin forms primary mass of tooth (is harder than bone)
- each root covered w/ cementum
- external surface of dentin = layer of enamel
- centre = pulp cavity that contains connective tissue called pulp
- root canal opens into CT through opening called apical foramen (where blood vessels & nerves pass through this opening)
20
Q
Teeth - the 2 sets that develop and erupt in normal lifetime
-number of teeth
A
- Deciduous teeth: erupt between 6-30 months, 20 in number (often called milk teeth)
- Permanent teeth: replace deciduous teeth, 32 in number
21
Q
Permanent teeth
-4 types and what they’re used for
A
- Incisors: most anteriorly placed, shaped like chisels, single root (slicing/cutting)
- Canines: posterolateral to incisors, pointed tips (puncturing/tearing)
- Premolars: posterolateral to canines, have flat crowns w/ prominent ridges called cusps (crushing/grinding)
- Molars: thickest and most posterior teeth (crushing/grinding)
22
Q
Pharynx
- shared by
- 3 skeletal muscles -> what they do
- blood supply
A
- shared by respiratory & digestive systems
- 3 skeletal muscle pairs of paryngeal constrictors (superior, middle & inferior)
- participate in swallowing
- Branches of external carotid arteries supply pharynx
- internal jugular veins drain the pharynx
23
Q
Oesophagus
- what it does
- length
- oesophageal hiatus
A
- Tubular passageway that conducts ingested materials from pharynx to stomach
- Passes through opening in diaphragm (oesophageal hiatus) as it connects to stomach
- approx 25 cm long (anterior to vertebral bodies)
- 1.5cm in abdomen before changing into stomach
24
Q
Oesophagus
- 3 Layers
- 2 sphincters & what they control
A
- Layers; Mucosa (inner), Mucularis mucosa (voluntary & involuntary mucles), advantitia (Connects oesophagus to other body parts)
- 2 sphincters;
1. Superior Oesophageal sphincter: at junction of pharynx & oesophagus -> closes during inhalation preventing air from entering GI tract
2. Inferior oesophageal sphincter: at juction of eosphagus and stomach - prevents materials from regurgitating from stomach into oesophagus
25
Stomach
- where found in abdomen
- what it does
- chyme
- 3 layers of muscle
- Upper left quadrant of abdomen
- Continues mechanical & chem digestion of bolus
- bolus eventually processed into paste-like soup called Chyme (through enzymes & acids)
- 3 layers of muscle to aid in mechanical processing of ingested materials
- longitudinal, circular & oblique layers
26
Stomach (4 regions)
- 4 regions;
1. Cardia
2. Fundus
3. Body
4. Pylorus
27
Stomach
- inferior & superior border
- rugae -> what they are & what they do
- inferior border = greater curvature
- superior border = inferior curvature
- Internal surface is thrown into folds called gastric folds (rugae)
- increases surface area (allows stomach to expand & disend)
28
Wall of the Stomach
- cells
- depressions (name & function)
- Lined by simple columnar epithelium (even tho little absorption occurs in stomach)
- Stomach lining is indented by numerous depressions called gastric pits (where substances secreted into)
29
Gastric Pits
-4 layers
Gastric Secretion
- Layers: Mucosa (epithelium & CT -lamina propria), submucosa (areolar packing tissue), Muscularis, serosa (outer layer - part of peritoneum)
- Gastric secretion: along & at base of gastric pits - are the openings of gastric glands that secrete products into stomach
30
Gastric Glands
-5 types of cells found within
1. Surface mucous cells - secretes mucin (protective lining of stomach)
2. Mucous neck cells - secretes acidic mucin
3. Parietal cells - scretes hydrochloric acid & intrinsic factor (helps bind to vitamin B12 so it can be absorbed)
4. Chief cells - secretes pepsinogen (precursor to pepsin - breaks down protein)
5. Enteroendocrine cells - secretes gastrin (gets picked up by surrounding blood cells - acts on muscle layers)
31
Small Intestine
- what it does
- length
* is last part of chemical digestion & responsible for absorbing most of nutrients
- ingested materials spend at lest 12 hours in small intestine
- approx 6 meters long in unembalmed cadaver (shorter in living due to muscle tone)
32
Small intestine
-3 segments
1. Duodenum (10 inches)
2. Jejunum (7.5 feet)
3. Ileum (10.8 feet)
33
Duodenum
- shape & location
- where bile & pancreatic secretions enter duodenum
- C-shaped
- upper right quadrant
- becomes continuous w/ jejunum at duodenojejunal flexure
- major duodenal pailla is site where bile & pancreatic secretions enter duodenum
- phloric sphinctor moderates how much chyme enters duodenum
34
Jejunum
- what it is
- features
- Middle portion of small intestine
- primary region for chem. digestion & nutrient absorption
- tortous structure - goes back and forth and twists
35
Ileum
-what it is & where it terminates
- Last segment of small intestine
| - distal end terminates at ileocecal valve (sphincter that controls entry of materials into large intestine)
36
Histology of small intestine
-layers
- Internally; mucosal & submucosal tunics thrown into folds called circular folds (plicae circularis)
- villi = microscopic fingerlike projections seen on surface of circular folds
- Microvilli = microscopic fingerlike projections seen on the surface of villi
* Lots of layers to increase SA w/in small intestine to increase absorption
37
Large Intestine
-features & function
- forms 3 sided perimeter around centrally located small intestine
- diameter is 6.5cm
- absorbs fluids and ions and compacts undigestible wastes and solidifies them in faeces
- also stores faeces until defecation
38
Structures in Large Intestine (7)
- Cecum
- ascending colon
- transverse colon
- descending colon
- sigmoid colon
- rectum
- anal canal
39
Cecum
- first part of large intestine
- blind sac located in lower right quadrant of abdomen
- Ileocecal valve represents junction between small & large intestine
40
Ascending Colon
- where originates
- bend in colon (name)
- Originates at ileocecal valve & ascends right side of abdomen
- as approaches inferior border of liver, makes 90 degree turn toward left side of abdominal cavity
- bend in colon called right colic flexure (hepatic flexure)
41
Transverse Colon
- where originates
- bend in colon (name)
- Originates at right colic flexure & approaches the spleen in upper left abdominal quadrant
- Suspended by transverse mesocolon
- makes 90 degree turn inferiorly at spleen - called left colic flexure (splenic flexure)
42
Descending Colon
- where originates
- what makes contact w/ and where terminates
- originates at left colic flexure
- found along left side of abdomen
- makes contact w/ iliac fossa & terminates into sigmoid colon
43
Sigmoid Colon
- shape
- where terminates
- Shape resembles letter S
- Turns inferomedially & is suspended by sigmoid mesentery
- terminates at rectum
44
Rectum
- what is it
- rectal valves
- where terminates
- Muscular tube that readily expands to store accumulated faecal material prior to defecation
- three thick, transverse folds of rectum (called rectal valves) ensure faecal material retained during passage of gas
- terminates at anal canal
45
Anal Canal
- what it is
- what it passes through
- sphincters (2)
- Terminal few centimeters of large intestine
- passes through levator ani muscles of pelvic floor
- anal columns line internal surface of anal canal
- anal sinuses secrete mucin for lubrication during defecation
- internal & external anal sphincters open & close anal canal during defecation
- under parasympathetic & sympathetic control
46
Histology of large intestine
-Lined w/ simple columnar epithelium and goblet cells
47
Muscular Wall of large intestine
- Longitudinal muscle is incomplete, forming bundles called teniae coli (helps move chyme along large intestine)
- bunch into many sacs called haustra
- extending off external surface of haustra are lobules of fat called omental appendices (aka epiploic appendages)
- function of these unknown
48
Peritoneum
-2 layers
- Abdominopelvic cavity covered w/ moist serous membranes
- parietal peritoneum: lines inside surface of body wall
- visceral peritoneum: covers surface of internal organs
49
Peritoneum
- intraperitoneal organs
- retroperitoneal organs
*e.g. of both
- Intraperitoneal organs = organs that are completely surrounded by visceral peritoneum (include stomach & most of small intestines)
- Retroperitoneal organs = organs that lie in direct contact w/ posterior abdominal & pelvic walls
- only covered on their anterolateral surfaces w/ visceral peritoneum
- e.g. pancreas, ascending & descending colon of large intestines & rectum
50
Mesenteries
- what they do
- what are sandwiched between them
q-Folds of peritoneum that support and stabilize intraperitoneal GI tract organs
-blood vessels, lymphatic vessels and nerves sandwiched between 2 folds & supply digestive organs
51
Mesenteries
- Greater & lesser omentum
- Mesentery proper
- Mesocolon
- Greater omentum: extends inferiorly like apron from greater curvature of stomach & covers most of abdominal organs
- Lesser omentum: connects lesser curvature of stomach & proximal end of duodenum to liver
- Mesentery proper: suspends most of small intestines from posterior abdominal wall (acts as anchor)
- Mesocolon: Peritoneal fold that attaches parts of large intestine to psoterior abdominal wall
52
Wall of abdominal GI tract (deep to superficial)
- Mucosa
- submucosa
- muscularis
- adventitia or serosa
53
Wall of abdominal GI tract; Mucosa
-3 layers
- 3 components to this deepest layer;
1. Superficial epithelium
2. Underlying areolar CT called lamina propria
3. Thin layer of smooth muscle, called muscularis mucosae
54
Wall of abdominal GI tract; Submucosa (4 components)
- Lymphatic ducts
- Mucin-secreting glands
- Blood vessels
- nerves
55
Wall of abdominal GI tract; Muscularis
- 2 layers of smooth muscles
- 2 exceptions
-2 layers of smooth muscles;
1. Inner circular layer - constricts lumen & forms sphincters
2. Outer longitudinal layer: shorten the tube
*together allow movement of chyme
Two exceptions;
-oesophagus has mix of both smooth & skeletal muscle
-stomach contains 3 layers of smooth muscle
56
Wall of abdominal GI tract; Adventitia or serosa
- Outermost layer
| - Areolar CT w/ collagen & elastin fibres
57
Blood flow through Gastrointestinal tract
-3 unpaired arteries
- 3 unpaired arteries emerge from anterior wall of descending abdominal aorta (are responsible for supplying organs of GI tract)
1. Celiac trunk (stomach, liver & spleen)
2. Superior Mesenteric artery (small intestine, pancrease & right colon)
3. Inferior mesenteric artery (left colon)
58
Venous return from abdomen
- Hepatic portal system is network of veins that drains blood from GI organs and shunts blood to liver
- Hepatic portal vein delivers nutrient-rich blood to liver
- formed by fusion of three abdominal veins (Inferior mesenteric vain (distal parts of colon), splenic vein (draining spleen, pancrease & stomach), superior mesenteric vein (small intestine, proximal part of colon, pancrease & stomach)
*hepatic vein collects blood from liver & returns to inferior vena cava
59
Lymphatic Vessels & structures
- Lacteals are present in villi or small intestines
- lymph ducts transport lymph to cisterna chyli (drains into thracic duct)
- lymphtic structures called MALT (mucosa-associated lymphatic tissue) found in small intestine & appendix
- these aggregate nodules called peyer patches
60
Accessory Digestive Organs
* not part of long GI tube; often develop as outgrowths of that tube
- teeth
- tongue
- salivary glands
- liver
- gall bladder
- pancrease
61
Liver
- location
- 4 lobes
- Located in right quadrant of abdomen
- weighs 1-2kg
- covered in a CT capsule & visceral peritoneum
- 4 lobes;
- right lobe
- left lobe
- caudate lobe
- quadrate lobe
62
Liver
-structures that make up shape of letter H
- Along inferior surface of liver, several structures make shape of letter H;
1. Inferior vena cava & ligamentum venous (remnant of fetal circulation) form inferior vertical parts
2. Gall bladder & round ligament form superior vertical parts
3. Porta hepatis represents horizontal crossbar; where blood vessels and lymphatic vessels, bile ducts & nerves enter and leave liver
63
Gall Bladder
- location
- function
- cystic duct
- Embedded on inferior surface of liver
- functions to collect & concentrate bile
- cystic duct connects gall bladder to common bile duct
64
Pancreas -functions
- Has both endocrine & exocrine functions
- exocrine functions; involve secreting digestive enzymes & bicarbonate (collectively called pancreatic juices) into duodenum via pancreatic duct into duodenum
65
Biliary Apparatus
- what it is
- function
- Network of thin ducts that transport bile from liver and gall bladder to duodenum
- Function of gall bladder is storage (not production) of bile
66
Biliary Apparatus
-what things merge to form
- left & right lobes of liver drain bile into left & right hepatic ducts
- merge to form the common hepatic duct
- cystic duct & common hepatic duct merge to form common bile duct
- common hepatic duct and main pancreatic duct enter duodenum through hepatopancreatic ampulla
67
Phases of swallowing
- what it is also called
- 3 phases
```
-Delutition - swallowing
3 phases;
-voluntary phase
-pharyngeal phase
-oesophageal phase
```
68
Phases of swallowing - detail
- Voluntary phase: Bolus of food pushed by tongue against hard palate and moved to oreophaynx
- Pharyngeal phase (involuntary): as bolus moves into oseopharynx, soft palate and uvula close off nasopharynx, and larynx elevates so epiglottis closes over laryneal opening
- esophageal phase (involuntary): contractions of esophageal muscle push bolus toward stomach; soft palate, uvula and larynx return to their pre-swalling positions
69
Peristalsis & segmentation
*propulsion of food along GI tube involves 2 types of movement:
-peristalsis
-segmentation
Peristalsis: ripple-like wave of muscular contraction that forces material to move further along GI tract
Segmetation: churning & mixing of material helping to disperse material and mix it and combine it with digestive organ secretions
