Session 1 Flashcards
1
Q
Purpose of gut
A
Ingest, digest, and absorb what’s needed
Egest what we don’t need
2
Q
Describe the gut as a tube
A
Has Inputs, is divided into regions (usually by sphincter)
3
Q
What is needed to create correct environment
A
Water, acid, HCO3 and enzymes
4
Q
The lumen of the gut is what type of surface
A
External (lined with epithelia)
5
Q
Which parts of the gut need to temporarily store food
A
Stomach and colon
6
Q
Control of gut involved which notable nervous system
A
Enteric (intrinsic)
7
Q
Describe the enteric nervous system
A
Semi-autonomous, in gut- controlling motor functions, immune function, blood flow, secretions, and transport across mucosa
8
Q
Where is enteric nervous system mostly contained
A
In submucosa (Meissner’s plexus) and between external muscle layers (Auerbach’s plexus)
9
Q
enteric nervous system is heavily interlinked with
A
Both divisions of the autonomic nervous system
10
Q
Perception of visceral abdominal pain is related to
A
Structure of sympathetic innervation to the gut
11
Q
How many layers does the gut tube have
A
4
12
Q
Name the layers of the gut tube
A
Mucosa, submucosa, external muscle layers and serosa
13
Q
Describe mucosa
A
Selectively permeable interface layer between the gut lumen - facilitates movement of molecules (absorption and secretion)
Deeper layers contain muscle, nerve plexuses and blood and lymph vessels
14
Q
What is an enterocyte
A
Cell located in intestine that is specialised to absorb. Modified to include micro villi
15
Q
What are micro villi
A
Very fine microscopic cellular protrusions designed to massively increase surface area
16
Q
What are goblet cells
A
Specialised cells that secrete mucus- increase in number from duodenum to colon.
17
Q
What does mucus do
A
Protects the gut epithelium from friction, chemical damage and bacteria
18
Q
Describe the internal surface of the gut
A
Not smooth- much folding.
19
Q
Describe the different types of folds
A
Rugae in stomach - temporary
Plica circulares in SI- permanent
Haustra in colon (result from contraction of the longitudinal muscle layer)
20
Q
Describe surface of small intestine
A
Finger like projections called villi, lined mainly by enterocytes
21
Q
What are crypts
A
Invaginations of the epithelial surface of the small intestine and are present in both small and large intestine
Contain stem cells, paneth cells and enteroendocrine cells (specialised)
22
Q
Stem cells divide and differentiate into other epithelial cells every
A
2-4 days
23
Q
2 major organs that deliver gut secretions
A
Liver and pancreas
24
Q
Other sources of gut secretions
A
Saliva, gastric and intestinal secretions
25
4 major muscle groups that form anterolateral abdominal wall
External oblique, internal oblique, transverse abdominus
Rectus abdominus
26
Describe muscles forming anterolateral abdominal wall
Lateral muscles with flat tendons (aponeuroses) project anteriorly to envelop the midline rectus abdominus muscle in a sheath (rectus sheath)
27
Describe peritoneal cavity
Mesothelium lined cavity that contains lubricating fluid - potential space formed by continuous layer of peritoneum
28
What is the name for the peritoneum that is in contact with the abdominal wall
Parietal peritoneum
29
What is the name for the peritoneum that envelops the abdominal viscera
Visceral peritoneum
30
What is the cavity
The space that lies between the parietal peritoneum and the visceral peritoneum
31
Difference in peritoneal cavity in males and females
In males it is enclosed but in females it is open at the entrance to the fallopian tubes
32
What happens as the peritoneum reflects off the abdominal wall
Envelopes viscera
33
What happens if the peritoneum folds back on itself
Mesentery is formed
34
What is mesentry
Double layer of peritoneum
Fat and Blood and lymph vessels lie between
35
Abdominal viscera that are enveloped in peritoneum are termed
Intraperitoneal structures
36
Abdominal viscera that lie behind the peritoneum are termed
Retroperitoneal structures
37
Order of travel in alimentary canal
Mouth, Oesophagus, Stomach, Pancreas, Duodenum of SI, Jejunum of SI, Ileum of SI, Cecum of LI, LI, Anus
38
Functions of mouth
Physical breakdown of food
Initial digestive enzymes released
Infection control
39
Functions of oesophagus
Rapid transport of bolus to stomach through thorax
Upper Oesophageal Sphincter - prevents air from entering GI tract
Lower Oesophageal Sphincter- prevents reflux into oesophagus
40
Functions of stomach
Storage facility
Produce chyme
Infection control (HCL)
Secrete intrinsic factor (Vit B 12)
41
What is chyme
Fluid that passes out from stomach that consists of gastric secretions and partially digested food
42
Functions of chyme
Physical breakdown
Chemical breakdown (proteases and acid)
Digestion started
Storage
43
What is duodenum
Start of small intestine
44
Functions of duodenum
Neutralisation/osmotic stabilisation of chyme - HCO3 rich secretions (bicarbonate rich secretions from pancreas and liver)
Digestion wrapping up (pancreatic secretions and bile from liver)
45
What is the osmotic property of chyme
Hypertonic- lots of water from gut vasculature
46
How and why do liver and pancreas connect to SI
Connect to Second part of duodenum through a common entrance
Deliver bile and pancreatic secretions into gut tube
47
What is released in duodenum of SI to help protein breakdown
Pepsin
48
Property of Jejenum/ileum
Lots of folds = large s.a.
49
Roles of Jejenum/ileum
Final digestion, nutrient absorption (mainly jejenum), water/electrolyte absorption (mainly ileum), bile recurculation (ileum), B12 absorption (terminal ileum)
50
What is terminal ileum
End of ileum just before start of large bowel
51
Functions of large bowel
Final water absorption, temporary storage, final electrolyte absorption, bile salt absorption, production of some SCFAs (carbs)
52
Interesting thing about final water absorption in large bowel
energy dependent process as against conc grad
53
Purpose of rectum/anus
Defacation
54
Feature of rectum
When stretched sends signals to poo as usually empty
55
Big difference between internal environments of small and large intestine
SI = relatively sterile
LI = lots of bacteria
56
Features of water absorption in large and small bowel
One of main functions of Large bowel, but small bowel absorbs a greater volume of water overall
57
Protective feature in large intestine
Lots of mucus secretion to provide barrier between bacteria and epithelium
58
Structures deep in the abdominal cavity
Kidneys, Spleen
59
Structures middle in the abdominal cavity
Stomach, small intestine, Liver
60
Structure top in abdominal cavity
Large intestine
61
What is the peritoneal cavity made of
Layers made of simple squamous epithelium (serous)
62
What are mesentries
Double folds in peritoneum
63
Why does line between the intraperitoneal structure of stomach and retroperitoneal structure not count as mesentery
Short and doesn’t allow stomach to move like SI
64
What does a mesentary do
Allows passage of blood vessels and lymphatics and various other things to go from retroperitoneal space to the viscera
65
Intra peritoneal viscera is enveloped by
Peritoneal cavity
66
What connects the liver and stomach
Ligament- double fold of peritoneum connecting viscera but does not connect to retroperitoneal space
67
What is an aponeurosis
Flattened tendon
68
Which muscles have aponeurosis
External and internal oblique, transverse abdominus
69
External oblique Origin, insertion, innervation and action
Origin- 5th-12th rib
Insertion- iliac crest, inguinal ligaments, linea alba
Action- compress abdominal viscera, flex trunk and rotate trunk to opposite side
Innervation- anterior rami T7 to T12
70
Internal oblique origin, insertion, action and innervation
Origin- lateral portion of inguinal ligament, iliac crest, thoracolumbar fascia
Insertion- pubic crest, linea alba
Action- compress abdominal viscera, flex trunk and rotate trunk to same side
Innervation- anterior rami T7 to T12, L1
71
Transverse abdominus origins, insertions, action and innervation
Origin- costal cartilages of lower ribs, thoracolumbar fascia, medial lip of iliac crest, inguinal ligament
Insertion- via aponeurosis, linea alba, pubic crest and internal oblique
Action- compress abdominal viscera, important for core stability
Innervation- anterior rami T7 to T12, and L1
72
Rectus abdominus origin, insertion and action
Origin- pubic crest, tubercle and symphysis
Insertions- costal cartilages of ribs 5-7, zephoid process
73
Features of rectus abdomninus
Paired muscle, tendinous intersections = 6 pack
74
What is the rectus sheath
Aponeurosis of the lateral muscles surrounding the rectus abdominus
75
What is arcuate line
Lower limit of the posterior layer of rectus sheath
Roughly halfway between umbilicus and pubic crest
76
What is the posterior layer of the rectus sheath
Parietal peritoneum
77
4 layers of gut external surface
Mucosa (innermost), submucosa, external muscle layers, serosa (outermost)
78
What is the mucosa layer made up of
Epithelial layer and lamina propria, then muscularis mucosa
79
Characteristics of epithelial layer of mucosa
Selectively permeable barrier
Facilitate transport and digestion of food
Promote absorption
Produce hormones
Produce mucus
80
Characteristics of lamina propria of mucosa
Lots of lymphoid nodules and macrophages
Produced antibodies (mainly IgA which is resistant to proteases) - protects against bacteria or viral invasion
81
Distribution of epithelia from distal oesophagus to distal anal canal
Stratified squamous prior to distal oesophagus, then columnar
82
important features of muscularis mucosae of mucosa layer
Layers of smooth muscle oriented in different directions
Keeps epithelium in contact with gut contents
Helps keep crypt contents dynamic
83
Submucosa characteristics
Contains dense connective tissue, blood vessels, glands, lymphoid tissue
Contains submucosa plexus (Meissner’s)
84
External muscle layer
Inner circular muscle - reduced width when constrict (myenteric/Auerbach’s plexus) - Muscularis propria
Outer longitudinal muscle reduces length
85
What are serosa layer features
Blood and lymph vessels and adipose tissue
Continuous with mesenteries
86
Characteristics of stratified squamous epithelium
Non keratinised (not concerned about water loss), often secrete mucous, resists abrasion
87
Where in the gut are stratified squamous cells found
Oesophagus and distal anus
88
Where in the gut are simple columnar cells found
Stomach to proximal anus
89
Describe the cells that line the stomach
Surface mucous cells- line gastric mucosa/pits, secrete mucus/HCO3 that forms barrier to stomach acid
90
Predominant cell of small intestine and colon function
Enterocyte- one cell thick
Transport nutrients through- apical membrane, basolateral membrane
Blood vessels/lymphatics lie immediately below the enterocyte
91
What gives large SA for absorptive areas in SI
Permanent folds, villi, microviili
92
Characteristics of intestines
Goblet cells- mucus compresses nucleus to base, increase from duodenum to colon, scattered between enterocyte
93
In intestines, mucus protects epithelia from
Friction (acts as lubricant), chemical damage (acidic environment), Bacterial inflammation (forms physical barrier)
94
Features of crypts
Enteroendocrine cells
Stem cells
Panneth cells
Villi
Anti bacterial proteins
95
What are enteroendocrine cells
Predominantly located deeper in crypts and gastric glands
Secrete hormones that control the function of the gut
96
What do enteroendocrine cells secrete
Gastrin, Cholecystokinin, Secretin
97
What do stem cells in crypts do
Constantly divide to replace epithelia every 2-4 days
98
What do paneth cells do
Base of crypts, secrete antibacterial proteins, protect stem cells
99
What is the specialised gland in duodenum
Brunner’s glands- produce alkaline mucoid material from mucosa layer. Counteract very acidic chyme
100
Where does most fat, proteins and carbs go
Fat to lymph
Proteins and carbs to blood
101
Which specialised cells are present in colon
Goblet cells (form crypts), stem cells, enteroendocrine cells, colonocytes (tall columnar epithelia)
102
How is water movement in colon controlled
Columnar cells use sodium transfer in lateral intercellular spaces
103
Describe para and symp in terms of pre and post
Para is long pre
And symp is short pre and long post
104
Key components of parasympathetic nervous system
Vagus nerve, pelvic splanchnic nerves S2-S4
105
In parasympathetic, post ganglionic fibres release
Acetylcholine, peptides (gastrin releasing peptide and vaso inhibitory peptide)
106
What do preganglionic fibres of Parasympathetic nervous system do
Synapse in walls of viscera to innervation smooth muscle/endocrine and secretory cells
107
What controls sympathetic nervous system
T5 to L2
108
how does the sympathetic nervous system pass through the paravertebral sympathetic trunk
Without synapsing
109
Sympathetic nervous system T5-L2 forms
Abdominopelvic presynaptic splanchnic nerves-
Greater T5-9
Lesser T10-11
Least T12
110
What do splanchnic nerves synapse with
Prevertebral ganglia, - coeliac, renal, superior mesenteric, inferior mesenteric and others
Mainly innervates blood vessels
111
What does the vagus nerve innervation
Oesophagus-transverse colon
112
What is pelvic nerve innervation
Transverse colon - anal canal
Long preganglionic fibres, extend to myenteric and submucosal plexuses, cholinergic and peptigergic
113
What does parasympathetic do
Stimulate GI function
114
Sympathetic nervous system characteristics
Short pre ganglionic fibres
Post ganglionic fibres extend to myenteric and submucosal plexuses- release norepinephrine
Generally inhibits GI function
115
Where does enteric nervous system exist from
Oesophagus to anus
116
What are the 2 main plexuses of enteric nervous system
Submucosal- (Meissner’s) in submucosa
Myenteric (Auerbach’s) in between circular and longitudinal muscle
117
What are endocrine hormones
Peptides released from endocrine cells into portal circulation, pass through liver, enter systemic circulation
118
What are paracrine hormones
Peptides released by endocrine cells, act in local environment, diffuse short distances
119
What are neurocrine hormones
Peptides released by neurones in the GI tract
Released after action potential
Example- GRP (gastrin releasing peptide), increases release of gastrin from G cells
120
How is gastrin released
G cells in antrum of stomach, increases gastric acid secretion
121
what causes release of gastrin
Stretch, amino acids, small peptides
122
How is Cholecystokinin CKK produced
I cells in duodenum and jejenum
Increases pancreatic/gallbladder secretions
(Stimulated by fat and protein, gall bladder contracts, pancreas stimulated, relaxes sphincter of Oddi)
123
How is secretin produced
By S cells in duodenum, Stimulated by H+ and fatty acids, increases HCO3 from pancreas/gallbladder, decreases gastric acid secretion
124
Explain action of gastric inhibitory polypeptide GIP
Cells in duodenum and Jejenum
Stimulated by sugars, amino acids and fatty acids
Increases insulin
Decreased gastric acid secretion
125
How does somatostatin work
Paracrine- low pH = D cells produce it, which causes less Gastrin produced by G cells
