Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Medicine Year 2 > GI Topic 4 - Lower GI Tract, Diarrhoeal Diseases > Flashcards

GI Topic 4 - Lower GI Tract, Diarrhoeal Diseases Flashcards

1
Q

What causes inflammatory diarrhoea?

A

Widespread destruction of absorptive epithelium - insufficient water absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the gastrocolic reflex?

A

Increased colonic motility after a meal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe water movement in the intestines

A
  • Water always moves to correct osmotic imbalance
  • Small intestine
    • Sodium is actively absorbed by co-transport with glucose/amino acids, water follows sodium and is absorbed
    • Cl-/HCO3- antiporter pumps Cl- into the lumen, Na+ follows to correct the electrochemical gradient, water follows and is secreted
  • Large intestine
    • Osmotic gradient produced by Na+ absorption - water follows
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Which antibiotics affect the gut microflora?

A

4 C’s - clindamycin, coamoxiclav, cephalosporins, ciprofloaxin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe the structure of the caecum

A

Blind-ended pouch, attached to the ileum at the ileocaecal valve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe the motility of the large intestines

A
  • Short duration and long duration contractions
  • Mixing movements - circular and longitudinal muscle contraction (haustrations)
    • Ensures all contents are exposed to the intestinal wall - absorption of water/electrolytes
  • Propulsive movements - slow, from prolonged contractions
  • Mass movements - 10-30 minutes every 12 hours
    • Contraction of 20cm+ of colon - propel faecal material en masse through colon
    • Result from distention of stomach and duodenum/irritation of colon
    • Stimulated by extrinsic autonomic nerves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the characteristics of inflammatory diarrhoea?

A

Low volume, bloody

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why is the microflora of the large intestine so extensive compared with other parts of the GI tract?

A
  • Less movement
  • Less acidic pH (buffered by bicarbonate)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where is bacterial activity highest in the colon?

A

Most activity in the proximal colon - distal more for storage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How are diarrhoeal diseases treated/managed?

A
  • Prevention - vaccination (e.g. rotavirus, measles), improve sanitation
  • Rehydration
  • Antibiotics (if bacterial)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the structure of the external anal sphincter

A
  • Lower 2/3 (overlaps with internal sphincter)
  • Voluntary
  • Joins with puborectalis muscle of the pelvic floor superiorly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Give examples of organisms which cause inflammatory enteric infections

A

Shigella, C. diff

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Give examples of organisms which cause non-inflammatory enteric infections

A

Vibrio cholerae, staph. aureus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

List the pathogenic mechanism types of enteric bacterial toxins

A
  • Neurotoxin e.g. clostridium botulinum, staph. aureus, bacillus cerus
  • Secretory (most common) e.g. Vibrio cholera, E. Coli, salmonella, shigella dysernteriae
  • Cytotoxin e.g. shigella, C. Diff, H. Pylori
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the function of the anal canal?

A

Defecation and maintaining faecal continence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the consequences of hypo/hyperkalaemia?

A

Arrhythmias

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the benefits of short chain fatty acids produces by gut microflora?

A
  • Increase cell proliferation in gut
  • Promote water absorption, prevent osmotic diarrhoea
  • Inhibit growth of pathogenic bacteria
  • Energy sources - acetic acid for fat synthesis, propionic acid for gluconeogenesis
  • Butyric - fuel for colonic cells, programmed cell death of cancer cells, increased Na+ and Cl- absorption
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Why is the anorectal flexure important?

A

Contributes to faecal continence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe the innervation of the colon

A
  • Mid-gut - SM plexus
  • Hind-gut - IM plexus
  • Parasympathetic - pelvic splanchnic nerves
  • Sympathetic - lumbar splanchnic nerves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe the action of colloids, when are they used?

A
  • High molecular weight, used to increase intravascular volume e.g. after major haemorrhage when the volume of the vascular bed decreases, for resuscitation
  • Initially nearly 100% remains intravascular
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe the venous drainage of the caecum

A

Ileocolic vein, drains into the superior mesenteric vein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What causes anorectal constipation?

A
  • Hirschprung’s disease - failure of migration of neural crest cells to distal colon - aganglionic and contracted
  • Obstructive defecation - paradoxical contraction of puborectalis + external sphincter during defection
  • Rectocoele
  • Anal fissure - associated pain on defecation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

List the flexures of the rectum

A
  • Sacral (anterior) and anorectal (posterior)
  • 3 lateral flexures - superior, intermediate and inferior
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

List the ions which are most important for movement of water in the intestines

A
  • Na+
  • Cl-
  • K+
  • HCO3-
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Describe the arterial supply of the anal canal

A
  • Above the pectinate line - superior rectal artery (branch of the inferior mesenteric artery) and middle rectal artery
  • Below the pectinate line - inferior rectal artery (branch of the internal pudendal artery), middle rectal artery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Which parts of the colon are intra/retroperitoneal?

A
  • Ascending and descending parts are retroperitoneal
  • Transverse and sigmoid parts are intraperitoneal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Describe the composition and types of crystalloids

A
  • Water and electrolytes - saline, dextrose, Ringer-lactate, Hartmann’s
  • Dextrose - contains glucose which is metabolised to water, used if Na+ is high, 10% remains IV
  • Saline - if sodium is low, 25% remains IV
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Describe the junction of the rectum and the anal canal

A
  • Anorectal ring joins the rectum and the anal canal
  • Muscular ring, made of internal and external anal sphincters and puborectalis muscle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Describe the relationship between enteric infection and Guillain-Barre Syndrome

A
  • Guillain-Barre neuropathic syndrome can occur after campylobacter infection
  • Neuropathic symptoms occur weeks to months after infection - weakness, neurological symptoms (demyelinating polyneuropathy)
  • Especially occurs in young men
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is the function of the caecum?

A

Used to be the site of cellulose digestion, now just storage of chyme

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

List the parts of the lower GI tract

A
  • Vermiform appendix
  • Caecum
  • Ascending colon
  • Transverse colon
  • Descending colon
  • Sigmoid colon
  • Rectum
  • Anal canal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Describe the innervation of the rectum

A
  • Sympathetic - lumbar splanchnic nerves, superior and infection hypogastric plexuses
  • Parasympathetic - S2-4 pelvic splanchnic nerves and inferior hypogastric plexuses
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is the role of Na+/K+ ATPase in fluid and electrolyte absorption?

A

Maintains electrochemical gradient

On basolateral surface of cells lining the intestines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

List the drugs which decrease colonic motility

A
  • Opiates (via Muscarinic receptors)
  • Anti-cholinergics
  • Loperamide (Muscarinic receptor agonist, decreases myenteric activity, slow transit - more water absorbed) - diarrhoea management
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

How is potassium absorbed in the intestines?

A

H+/K+ ATPase - K+ absorbed, H+ secreted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

How is defecation controlled?

A
  • Local enteric nervous control in the rectal wall stimulated by distention of the rectum - afferent signals to the myenteric plexus, peristaltic waves in the descending/sigmoid colon and rectum, forces faeces towards anus
  • Internal sphincter relaxed by inhibitory signals from myenteric plexus
  • If external relaxed voluntarily - defecation occurs
  • Parasympathetic defecation reflex - sacral spinal segments, pevic nerves - relax internal sphincter and increase peristaltic waves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

List the causes of osmotic diarrhoea

A
  • Laxatives
  • Antacids
  • Acarbose (alpha glucosidase inhibitor)
  • Orlistat (lipase inhibitor)
  • Digestive/pancreatic enzyme insufficiency
  • Inflammatory disease
  • Short bowel syndrome (or bowel resection)
  • Loss of enterocytes
  • Bacterial overgrowth
  • Lymphatic obstruction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Describe the venous drainage of the appendix

A

Appendicular vein, drains to ileocolic vein (drains to SMV)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Aside from SCFA, what substances do colonic flora produce?

A
  • Vitamin B12 - can’t be absorbed
  • Thiamine
  • Gases - CO2, H2, methane
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

How is the rectum structually different to the colon?

A

Rectum has no taenia coli, haustrations or epiploic appendices

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Describe the structure of the marginal artery

A
  • Formed from anastomoses of branches of the inferior mesenteric and superior mesenteric arteries
  • Gives rise to long, straight arterial branches - vasa recta
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

How is sodium absorbed in the intestines?

A
  • Co-transported with glucose and amino acids
  • Antiported - sodium/hydrogen exchange
  • Partially absorbed with Cl- - dragged by negative charge
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Where does the small intestine join the colon?

A

At the ileocaecal valve

44
Q

Describe the structure of the internal anal sphincter

A
  • Upper 2/3 of the anal canal
  • Involuntary smooth muscle
45
Q

What causes motility disorders of the colon?

A

Diabetes mellitus, post-surgical

46
Q

Describe the potassium content of the body

A

Plasma - 3.5-5.0 mmol/L

Total body - 3600 mmol

Daily intake - 30-100 mmol

47
Q

What is pseuodomembraneous collitis? How is it treated?

A
  • Caused by various infective agents e.g. C. diff
  • Results in distention of colon which can progress to toxic megacolon if untreated
  • Treated with vancomycin
48
Q

How can rehydration be acheived?

A
  • Oral rehydration solutions
  • IV solutions - colloids or crystalloids
49
Q

Describe the fluid replacement regimes

A
  • 500 ml - 2 hourly (emergency)
  • 500ml - 4 hourly
  • 500ml - 6 hourly (standard)
  • 500ml - 8 hourly (slow rehydration)
50
Q

Describe the arterial supply of the colon

A
  • Ascending
    • Ileocolic and right colic arteries (branches of superior mesenteric artery)
    • Ileocolic branches from anterior and posterior caecal branches
  • Transverse
    • Right colic and middle colic arteries (branches of superior mesenteric artery)
    • Left colic artery (branch of inferior mesenteric artery)
  • Descending
    • Left colic artery (branch of inferior mesenteric artery)
  • Sigmoid
    • Sigmnoid arteries (branch of inferior mesenteric artery)

Marginal artery (of Drummond) - supplies colon collaterally, in case of occlusion/stenosis

51
Q

Define diarrhoea

A

3+ loose, watery stools per day

52
Q

Describe the daily intake and excretion of water in the body

A
  • Intake = 2,000mL
  • Excretion =
    • Urine - 1200mL
    • GI tract - 100mL
    • Insensible loss (breathing and sweating) = 700-800mL
  • Turnover in the GI tract = 9000mL
53
Q

How is bicarbonate secreted/absorbed in the intestines?

A
  • Absorbed in the duodenum and jejunum - makes up for secretion in pancreatic juices/bile
    • Sodium ions absorbed in exchange for H+
    • H+ + HCO3- combines to form carbonic acid (H2CO3) which dissociates to form H2O and CO2
    • H2O absorbed/stays in gut, CO2 absorbed into blood and expired
  • Secreted in the ileum and large intestines
    • Antiporter - bicarbonate secreted, chloride absorbed
54
Q

What are the uses of Vancomycin?

A
  • Used as alternative in penicillin allergy
  • Used to treat C. Diff infection (oral)
55
Q

How long does it take for the contents of the colon to reach the rectum?

A

8-15 hours

56
Q

What is the histological difference between the colon and the rectum?

A

Shorter crypts of Leiberkuhn

57
Q

Define secretory diarrhoea

A

Endotoxins stimulate secretion, usually of Cl- ions via the CFTR transporter

58
Q

Describe the histological layers of the large intestines

A
  1. Mucosa - simple columnar epithelium, lamina propria with lacteals and network of capillaries + lymphatic nodules, muscularis mucosae
  2. Submucosa
  3. Muscularis propria - circular and longitudinal smooth muscle, arranged as 3 taenia coli
  4. Serosa - visceral peritoneum
59
Q

List the flexures of the colon

A
  • R colic (hepatic) flexure
  • L colic (splenic) flexure
  • Sigmoid flexure
60
Q

How is water absorbed in the intestines?

A
  • Through tight junctions between apical cells (paracellular)
  • Through cells (transcellular)
61
Q

How is Hirschpring’s disease treated?

A

Surgical resection of affected part

62
Q

Describe the innervation of the appendix and caecum

A
  • Sympathetic - ileocolic branch of the superior mesenteric plexus
  • Parasympathetic - vagus nerve
63
Q

Give examples of organisms which cause penetrating enteric infections

A

Salmonella typhi

64
Q

What GI risks are involved in antibiotic use

A
  • Particularly broad spectrum antibiotics - inhibit growth and metabolism of normal colonic flora
  • Increased risk of diarrhoea/infection e.g. C Diff.
65
Q

Describe the epithelium of the anal canal

A
  • Upper 2/3 - simple columnar
  • Lower 1/3 - stratified squamous
    • Above pectinate - non-keratinised
    • Below pectinate - keratinised
66
Q

Describe the location of the anal canal

A
  • In anal triangle of perineum between the left and right ischioanal fossae
  • 4cm long, terminates at anus
67
Q

How are short chain fatty acids utilised clinically?

A

SCFA enema - treatment of ulcerative collitis

68
Q

What is the function/structure of the CFTR transporter?

A
  • G protein coupled receptor, cAMP/PKA activate it by phosphorylation
  • Moves Cl- out of cells into the intestinal lumen
  • Na+ and therefore water follow
69
Q

Describe the types of enteric infections

A
  • Non-inflammatory - proximal small bowel, watery diarrhoea, no leukocytes, mild/no lactoferrin
  • Inflammatory - colon, dysentery, faecal leukocytes, high lactoferrin
  • Penetrating - distal small bowel, enteric fever, faecal leukocytes
70
Q

Describe the inferior portion of the rectum

A

Ampulla - temporary storage of faeces, passes through the pelvic floor, continuous with anal canal

71
Q

How can colonic transit be measured?

A
  • Senal X-Ray with radio-opaque markers
    • No marker seen - normal
    • Marker seen in rectosigmoid area - pelvic outlet obstruction
    • Marker scattered throughout colon - slow transit constipation
72
Q

Describe the venous drainage of the anal canal

A
  • Above the pectinate line - superior rectal vein, drains to the inferior mesenteric vein
  • Below the pectinate line - inferior rectal vein, drains to the internal pudendal vein
73
Q

Describe the location of the rectum

A
  • Begins at rectosigmoid junction - at level of S3
  • Retroperitoneal
  • 15cm long
74
Q

Describe the structure and function of the vermiform appendix

A
  • Highly variable position
  • Lots of lymphoid tissue
  • No vital function
75
Q

List the types of diarrhoea

A
  1. Osmotic
  2. Secretory
  3. Inflammatory
76
Q

List causes of inflammatory diarrhoea

A
  • Inflammatory bowel disease - Crohn’s, ulcerative collitis
  • Infectious disease - shigella, salmonella
  • Irritable colon
77
Q

What causes anorectal incontinence?

A
  • Excessive rectal distention - acute/chronic diarrhoeal disease, chronic constipation
  • Anal sphincter weakness - damage to muscle/pudendal nerve
78
Q

Describe the arterial supply of the appendix

A

Appendicular artery from the ileocolic artery

Travels in the mesoappendix - field of mesentery

79
Q

Define osmotic diarrhoea

A
  • Due to fluid accummulation in the GI tract
  • Fluid accummulates - rapid propulsion - reduced absorption of fluid - more fluid accummulation
  • Due to non-absorbable solutes/failure to digest or absorb nutrients
80
Q

What are the paracolic gutters?

A
  • Lateral to the ascending and descending colon, between the colon and posterior abdominal wall
  • Depression for materials to pass through
81
Q

Describe the venous drainage of the colon

A
  • Ascending - ileocolic and right colic veins, drain to SMV
  • Transverse - middle colic vein, drains to SMV
  • Descending - left colic vein, drains to IMV
  • Sigmoid - sigmoid veins, drain to IMV
82
Q

Describe the venous drainage of the rectum

A
  • Superior, middle and inferior rectal veins
  • Superior drains to the IMV
  • Middle drains to the internal iliac vein
  • Inferior drains to the internal pudendal vein
83
Q

How does the structure of the anal canal allow for maintenace of continence?

A

Internal and external anal sphincters collapse to prevent passage of faeces, except during defecation

84
Q

Describe the anatomical location of the caecum/appendix

A

R iliac fossa, intraperitoneal

85
Q

Describe the innervation of the anal canal

A
  • Above the pectinate line - inferior hypogastric plexus (detects stretch)
  • Below the pectinate line - inferior anal nerves (branches of the pudendal nerve)
    • Detects pain, temperature, touch and pressure
86
Q

How does spinal cord injury affect bowel function?

A
  • T12 or above - bowel opens spontaneously but without control (reflex arc intact)
  • Sacral nerve roots - flaccid bowel, no reflex arc, incontinence
87
Q

What must be taken into consideration when rehydrating?

A
  • Need to correct potential electrolyte shifts
  • Calculate rehydration rate/volume of fluids using daily need, anticipated loss and previous deficits
  • Check electrolye shifts, blood gases (acidosis due to bicarbonate loss), glucose, albumin, urea and creatinine, plasma osmolality
  • Speed of fluid replacement dependent on age, renal function and cardiovascular status
88
Q

How are SCFA absorbed?

A

Antiporter - HCO3- secreted

89
Q

What is the significance of E. Coli 0157?

A
  • Damages vascular endothelium - renal failure, haemolytic uraemia syndrome
  • Antibiotics contraindicated - results in release more toxins
  • Causes cytotoxic bloody diarrhoea
90
Q

Describe the maximum safe K+ supplementation

A
  • Maximum concentration - 40 mmol/L
  • Maximum rate - 10 mmol/L
91
Q

Describe the volume of fluid secreted and absorbed by the GI tract

A
  • Secretions
    • Salvia = 1.5L
    • Gastric juice = 2.5L
    • Bile = 0.5L
    • Pancreatic juice = 1.5mL
    • Instestinal secretions = 1L
  • Absorbed
    • Proximal colon = 150-2000mL
92
Q

Describe the distinct histological features of the colon

A
  • Crypts of Leiberkuhn - straight tubular glands down to the muscularis mucosae
  • Goblet cells - mucous for lubrication
  • Absorptive enterocytes - extract water and electrolytes
93
Q

Why are the colonic flora beneficial?

A

Convert 60g of carbohydrates (fibre, starch, oligosaccharides) per day to short chain fatty acids (acetic, proprionic, butyric acids) which are rapidly absorbed

94
Q

What is the prodominant type of micoflora which colonises the large intestine?

A

Mostly strict anaerobes e.g. Clostridium spp.

95
Q

Describe the process of defecation

A
  • Faeces moves into rectum - desire for defecation
  • Contraction of rectum, relaxation of anal sphincter
  • Involuntary defecation prevented by internal and external anal sphincters (external always constricted unless conscious signals inhibit)
96
Q

List the functions of the large intestine

A
  1. Absorb water and electrolyes - form solid faeces (first 1/2)
  2. Storage of faecal matter until expelled (second 1/2)
97
Q

List the drugs which increase colonic motility

A
  • Stimulant laxatives (short action, big effect)
  • Prucalopride (serotonin receptor agonist - for treating chronic constipation)
  • Linaclotide (guanylase C receptor agonist, increases Cl- and HCO3- secretion, increased fluid secretion, speeds transit) - IBS treatment
98
Q

Describe the location of the sigmoid colon

A
  • L lower quadrant
  • From L iliac fossa to the level of S3
  • S shape
  • Attached to posterior pelvic wall by sigmoid mesocolon (mesentery)
99
Q

List the signs of dehydration

A

Dry mucosa, reduced skin turgor, purple fingernails

100
Q

How are oral rehydration solutions designed to give the most efficient rehydration?

A
  • Contain glucose - needed to absorb sodium effectively
  • Reduced osmolarity - better absorbed
101
Q

List the causes of secretory diarrhoea

A
  • Rotavirus
  • E. Coli
  • Shigella
  • Campylobacter
  • Salmonella
  • Vibrio cholera
  • Cryptosporidium protozoa
  • Hormone-like peptides - carcinoid/Zollinger-Ellison’s syndrome
  • Drugs e.g. antidepressants
  • Metals, organic toxins + plant products
102
Q

Describe the arterial supply of the rectum

A
  • Superior rectal artery (terminal branch of the inferior mesenteric artery)
  • Middle rectal artery (branch of internal iliac artery)
  • Inferior rectal artery (branch of internal pudendal artery)
103
Q

Describe the arterial supply of the caecum

A
  • Ileocolic artery - branch of the superior mesenteric artery
  • Splits into anterior and posterior caecal arteries
104
Q

List the distinctive characteristics of the colon

A
  • Epiploic appendices - pouches filled with fat surface
  • Taenia coli = 3 strips of longitudinal muscle - mesocolic, free + omental coli, end at the rectosigmoid junction
  • Haustra - where taenia coli contract, gives sacculations
  • Wider diameter than small intestine
105
Q

How do endotoxins cause activation of CFTR? What effect does this have?

A
  • Endotoxins activate cAMP/PKA, CFTR is phosphorylated and therefore activated
  • Causes increased movement of Cl- and therefore water secretion into the intestinal lumen - secretory diarrhoea
106
Q

Describe the IV rehydration solutions with extreme osmolalities

A
  • Sodium bicarbonate (8.4%) - hyperosmotic, used only in extreme resuscitation
  • Saline (0.45%) - hypoosmotic, causes oedema

Medicine Year 2 (41 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions