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Flashcards in Digestive System Deck (69):
1

What organs in digestive system do (5)

-Ingest food
-Transport ingested food
-Digest material into smaller usable components
-absorb necessary nutrients into bloodstream
-expel waste products from body

2

2 Categories of Organs in digestive system

1. Digestive Organs: make up gastrointestinal tract (aka digestive tract or alimentary canal)
2. Accessory digestive organs: organs that aide in digestion

3

Digestive system functions (6)

-Ingestion
-Digestion
-Propulsion
-secretion
-Absorption
-Elimination of wastes

4

GI Tract Organs (6)

-Oral cavity
-Pharynx
-oesophagus
-stomach
-small intestine
-large intestine

5

Cheeks, Lips & Palate

-palate (2 types)

-uvula

-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

Cheeks, lips & palate

-Cheeks and lips

-labial fenulum

-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

What comprises the oral cavity

-Cheeks, lips & palate
-Tongue
-salivary glands
-teeth

8

Cheeks, Lips and Palate

-fauces
-2 muscles that bind it laterally
-palatine tonsils -> where found

-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

Tongue

-What it does
-bolus
-lingual frenulum (what it is & where it attaches)

-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

Gustation

-what is it
-Gustatory cells (what are they called?)
-where located

-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

Tongue Papillae (4 types)

1. Filiform papillae
2. Fungiform papillae
3. Vallate papillae (form a V shape)
4. Foliate papillae

12

Salivary Glands

-role

-5 functions

-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

3 pairs of salivary glands -> where all are located

*located external to oral cavity
1. Parotid glands
2. Submandibular glands
3. Sublingual glands

14

Salivary Glands; Parotid salivary glands

-where found
-how much saliva they produce

-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

Salivary glands; Submandibular glands

-where found
-how much saliva they produce

-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

Salivary glands; Sublingual salivary glands

-where found
-how much saliva they produce

-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

Salivary gland secretion (2 types)

-2 types of secretory cells found in glands;

1. Mucous cells: secrete mucin, which forms mucus upon hydration (provides lubrication in oral cavity)
2. Serous cells: secrete watery fluid containing ions, lysozyme and salivary amylase (involved in chemical digestion)

18

Salivary glands and types of secretion

-Parotoid = serous secretion
-Submandibular = mucous and serous secretions
-Sublingual = mucous and serous secretions

19

Teeth

-Parts of tooth
-dentin
-enamel
-centre of tooth
-root canal

-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

Teeth - the 2 sets that develop and erupt in normal lifetime

-number of teeth

1. Deciduous teeth: erupt between 6-30 months, 20 in number (often called milk teeth)
2. Permanent teeth: replace deciduous teeth, 32 in number

21

Permanent teeth

-4 types and what they're used for

-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

Pharynx

-shared by
-3 skeletal muscles -> what they do
-blood supply

-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

Oesophagus

-what it does
-length
-oesophageal hiatus

-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

Oesophagus

-3 Layers

-2 sphincters & what they control

-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