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Abdomen and Pelvis Anatomy and Pattern Recognition > digestive system > Flashcards

digestive system Flashcards

1
Q

overview of abdomen

A

The anatomical location for the abdomen is from the diaphragm to the pelvic inlet/ lower limbs

It is enclosed by the abdominal wall and the inner large peritoneal cavity

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2
Q

Functions of the abdominal cavity

A

. breathing = The abdominal wall relaxes to allow the thoracic cavity to expand and contracts to reduce the thoracic cavity (forcibly when coughing or sneezing)
. It contains and protects the major organs
. Increasing abdominal pressure = contraction of the abdominal wall assists in mictuation defecation and childbirth

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3
Q

Regional anatomy

A

• The abdomen can be divided as:
4 quadrants
- Median sagittal plane
- Axial plane at the level of the umbilicus and L3/4
9 regions
- 2 sagittal planes at the mid clavicle
- Axial subcostal plane – level of lower costal margin and L3
- Axial intertubercular plane – iliac crests / L5
- Although there is some variation, normally organs can be found in pre-determined areas

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4
Q

The abdominal wall

A

The anatomical landmarks for the abdominal wall are the
• Superior - Xiphisternum and lower costal margin
• Inferior – pelvis bones
• Posterior – spine
• It is made of 5 layers
Skin
Subcutaneous (adipose) tissue and superficial fascia
Muscles and fascia
Extra-peritoneal fascia / fat
Parietal peritoneum

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5
Q

The muscles of the abdomen

A

There are 5 paired muscles to meet the functions of the abdomen
• Each muscle has its own function
• It is separated in the midline by the linea alba fascia

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6
Q

Extraperitoneal fascia

A

Deep to the muscles
Between the parietal peritoneum and the muscles of the abdominal wall
Contains different amounts of fat (adipose tissue) – there is more posteriorly than anteriorly
Anteriorly – called pre-peritoneal
Posteriorly – called retro-peritoneal

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7
Q

Peritoneum

A

• This is the innermost layer of the abdominal wall
• It is a closed sac for men, unclosed in women (there is an opening for the uterine tubes)
It is a
• Continuous serous membrane
• Layer of simple squamous epithelium
• Supported by connective tissues
There are 2 layers names by its role / location
• Parietal – lines the abdominal wall / peritoneal cavity
• Visceral (serosal) – covering the organs

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8
Q

Peritoneal cavity

A

• The cavity only contains minimal serous fluid – 5-20ml
• Fluid has an important role in peritoneal homeostasis
• It is divided into 2 parts
greater sac - most of the space
lesser sac - smaller area

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9
Q

Within the peritoneal cavity

A

stomach
GI tract
spleen
tail of pancreas

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10
Q

Outside the peritoneal cavity

A

Urinary
• Adrenal glands
• Kidneys
• ureters
Vascular
• Aorta
• Inferior vena cava
Digestive
• Lower 2/3 rectum

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11
Q

omenta

A

2 layers which connect the stomach / first part of the duodenum to the other organs

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12
Q

Mesenteries

A

Surround and support loops of bowel, connecting to the posterior abdominal wall
It allows for some movement of bowel

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13
Q

Ligaments

A

There are 2 layers of peritoneum connecting organs to the abdominal wall
They are usually names after the structures they connect

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14
Q

The digestive system

A

• It converts food into energy and absorbs nutrients
main processes =
ingestion
propulsion
digestion (mechanical and chemical)
absorption
elimination

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15
Q

The GI tract

A

• Continuous hollow tube
• Approximately 30ft long in cadavers
• Food is always considered external to the body, it only contacts the inner lining
• The tissues are similar along the length of the canal with slight modifications to aid digestion
parts = mouth, pharynx oesophagus, stomach, small intestine, large intestine, rectum and anal canal

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16
Q

structure of GI tract

A

There are 4 basic tissue layers
• Mucosa
• Sub-mucosa
• Muscularis
• Serosa

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17
Q

Muscles of the GI tract

A

2 layers of mostly smooth muscle
• Inner circular
• Outer longitudinal
They are separated by lymphatic and neurovascular layers

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18
Q

Nerve supply of the GI tract

A

• There is intrinsic and extrinsic innervation
• All of the digestive system is innervated by the autonomic nervous system
Parasympathetic
• Increases secretions and motility
• Mostly the vagus nerve and sacral nerve
Sympathetic
• Decreases secretions and motility
• This is your spinal nerves along the spine

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19
Q

Blood supply to the digestive system – arterial

A

Arterial
Thoracic aorta
• Oesophageal arteries
Abdominal aorta
• Coeliac arteries – liver, spleen, stomach (T12 – L1)
• Superior mesenteric artery – pancreas, small intestine (L1/2)
• Inferior mesenteric artery – colon and rectum (L3)

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20
Q

Blood supply to the digestive system - venous

A

• Hepatic postal system in the liver

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21
Q

What is the aim of digestion?

A

• To break down food in preparation for absorption
It is mechanical
• There is movement along the GI tract
• Breaking down the food increases the surface area for absorption
• As the food passes through it mixes with chemicals / secretions
Chemical enzymes
• Amylase – carbohydrates (salivary glands and
pancreas)
• Proteases (pancreas) and hydrochloric acid (stomach) – proteins
• Bile (pancreas) and lipases (pancreas)- fats

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22
Q

mouth

A

Mouth
• Oral cavity
• Vestibule – the space between your teeth, gums, lips and cheeks
• The oral cavity is lined with the mucous membranes
• Contains mucus secreting goblet cells
• Consists of squamous epithelium

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23
Q

tongue

A

main functions
- mastication
- swallowing
- speech

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24
Q

The role of the tongue in digestion

A
  • grips food and positions it between the teeth
  • mixes food with saliva
  • forms a bolus of food
  • intiates swallowing
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25
Q

salivary glands

A

There are 3 bilateral pairs of glands which release saliva into the mouth through ducts
•Parotid
• Submandibular
• Sub-lingual

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26
Q

Oesophagus

A

This is a muscular tube
It begins distal to the pharynx at around the level of C6
Approximately 25cm long and 2cm in diameter
Lies in the midline posterior to the trachea and anterior to the spine
The cardiac sphincter prevents reflux of stomach contents

27
Q

Oesophagus - structure

A

• Outer layer is fibrous and attaches to the surrounding structures
• There is a muscle layer for peristalsis
• There are no digestive enzymes in the mucosal layer – no absorption
The arterial supply
• Thorax – branches off the thoracic aorta – oesophageal arteries
• Abdomen – inferior phrenic and left gastric artery
The venous drainage
• Thorax – azygous vein
• Abdomen – left gastric vein

28
Q

saliva

A

• Food is mixed with saliva which contains enzymes
• The enzymes are only activated in liquid and help to dissolve chemicals in food to aid taste
• Salivation is controlled by the autonomic nervous system.
• Parasympathetic –continuous secretion
• Sympathetic – works during stress or dehydration – dry mouth / thirst
• Chemicals in food stimulate the receptors in taste buds which result in secretion
• After eating there is a flow of saliva for cleaning and diluting any remaining chemicals

29
Q

swallowing

A

3 stages according to location of bolus; takes around 4-8 seconds (1 for fluid)

30
Q

stomach

A

c/j shaped
15-25 cm long

31
Q

regions of the stomach

A

Cardia
• Surrounds the cardio-oesophageal sphincter
Fundus
• The section lateral to the cardia
Body
• Mid portion
• Narrows inferiorly
Pylorus
• Consists of the antrum and canal
• Contains the pyloric sphincter which is continuous with the small intestine

32
Q

stomach layers

A

Serosa
• Serosa is continuous with the visceral peritoneum
• 3 muscle layers which allow churning and mixing

33
Q

stomach layers - mucosa

A

. Made up of simple columnar epithelium
• Contains mucus cells
• Has a protective alkaline layer to protect from acids and enzymes
• Gastric juices are secreted from gastric glands – up to 2-3l a day

34
Q

mechanical dogestion in the stomach

A
  • there are peristaltic waves every 15-20seconds
  • food is macerated
  • it is mixed with secretions to form chyme
  • the fundus secrion is mainly for storage - less movement
  • the rugae allow dor expansion and increase the surface area
35
Q

chemical digestion in the stomach

A
  • The food may be in the fundus for more than an hour before churning begins but the salivary amylase continues to work
  • Food is mixed with acidic gastric juices
  • Very small amounts of nutrients are absorbed
  • The epithelial cells are impermeable to most materials
  • Some water is absorbed
  • some drugs are absorbed
    • Aspirin
    • Alcohol
    • The stomach empties 2-4 hours after eating
    • Carbohydrate rich food is the quickest
    • Fatty food is the slowest
    • Each wave moves approximately 3mm of chyme through the sphincter into the duodenum
    Some drugs are absorbed
36
Q

small intestine

A

• Food is prepared in the small intestine so it can enter the cells of the body
• The small intestine is a muscular tube approx. 7m long from the pyloric sphincter to the ileocaecal sphincter
• Longest segment of digestive tract

37
Q

small intestine - divisions

A

Duodenum - 25cm long (5%)
Jejunum - 2.5m long (40%)
Ileum -3m long (55%

38
Q

duodenum

A

• C shaped
• Extends from the pyloric sphincter to the jejunum
Has 4 sections
• 1st – superior
• 2nd – descending
• 3rd – horizontal
• 4th - ascendin

39
Q

duodenum structure

A

• Surrounds the head of the pancreas
• Receives
Gastric chyme from the stomach
Digestive juices from the pancreas
Bile from the live

40
Q

Mechanical digestion in the small bowel.

A

•Contraction of circular muscle into segments
•Muscle fibres in middle of each segment contract –
dividing segment further
•First fibres relax -> large segment again
•Repeats – chyme sloshed back and forth
•Most rapid in duodenum
•After most of food absorbed segmentation stops and peristalsis begins
•Peristalsis migration reaches end of ileum in 90 –
120 minutes
•Chyme remains in small intestines 3 – 5 hours

41
Q

duodenum

A

The mucosa has villi to increase the surface area
Its function is to breakdown food using enzymes
It uses hormones to regulate the rate of stomach emptying

42
Q

jejunum

A

Has villi
• Has large circular folds to increase surface area of
mucosa
• Main function is to absorb previously digested food from the duodenum

43
Q

ileum

A

• There isn’t an obvious junction between the
jejunum and ileum
• Has smaller and thinner walls than the jejunum
• Function
Absorb B12 and bile salts
Absorb remaining products not absorbed in the
jejunum

44
Q

Large bowel

A

• Large because it has a larger diameter
• 1.5m long
• Differing diameters – 6-9cm
• No villi on the mucus membrane as there is no chemical digestion
• There are no structural alterations to increase surface area
• There are goblet cells with produce mucus to ease the passage of faeces

45
Q

Caecum and appendix

A

• Caecum – 6cm long
• Receives chyme from the ileum
• Has the appendix hanging from it

46
Q

Colon

A

Ascending
• 20cm long
• Has the hepatic flexure at distal end
Transverse
• Has hepatic and splenic flexure at either end
• Descending
• Left side of pelvis
Sigmoid
• S shaped. Projects medially

47
Q

Mechanical digestion in the large bowel

A

•Chyme enters cecum via ileo-caecal sphincter (Usually slowly)
•Gastro-colic reflex:
• Food entering stomach stimulates release of Gastrin into blood
•Gastrin plays a part in ileo-caecal sphincter relaxation
•Allows chyme to enter caecum from ileum
•Faeces in caecum triggers mass movement

48
Q

Mass movement of faeces

A

When caecum becomes distended the contraction of the ileocaecal sphincter increases
Chyme fills caecum and accumulates in ascending colon
Haustral churning –distended by contents, walls contract moving contents to next haustrum
Peristalsis also occurs but slower 2 – 3 contractions per minute
Mass peristalsis – strong peristaltic wave from mid transverse colon
Drives faeces into rectum
Occurs after meals – 3 – 4 times per day

49
Q

Chemical digestion in the large bowel

A

No enzymes secreted
Final stage of digestion – activity of bacteria in lumen
Bacteria:
Ferment any remaining carbohydrate
Releases hydrogen, CO2 and methane gas
Flatus – which becomes flatulence if excessive
Breakdown remaining proteins and amino acids
Decompose bilirubin to simpler pigments results in brown colour

50
Q

Absorption in the large bowel

A

Water
• Most water is absorbed in the large bowel
• The large bowel is important in maintaining homeostasis
Bacterial products
• Including vitamins – B and K

51
Q

Defaecation

A

•Elimination of indigestible residue
•When faeces into rectum by mass movement
defecation reflex initiated
•Spinal reflex:
• Causes walls of sigmoid colon and rectum to
contract
• Anal sphincters relax
• Faeces in anal canal messages to brain
• Voluntary decision to open external sphincter
• If not contraction ends and walls relax
• Next mass movement initiates new reflex

52
Q

What are the functions of the liver?

A

digestive
haematological
metabolism of nutrients
detoxification
mineral and vitamin storage
bile production
absorbs iron and vitamin K

53
Q

The liver

A

• Irregular wedge-shaped organ
• The liver is the largest gland in the body
• It is situated under the diaphragm in the right upper quadrant extending into the left upper quadrant
• It is largely protected by the ribs and overlies the stomach

54
Q

liver divisions

A

• It is divided into 4 lobes
Left lobe
Right lobe
• Subdivided into the caudate and quadrate lobes

55
Q

Blood supply to the liver

A

A large amount of blood is needed for metabolic functions
Hepatic artery – 400-500 ml/min 25%
Hepatic portal vein 1000-1200 ml/min 75%
hepatic veins return blood to the IVC

56
Q

Hepatocytes

A

metabolise proteins lipids and vitamins

57
Q

the gallbladder

A

• Sac like organ
• Situated on the inferior surface of the liver
• It stores and concentrates bile
• Bile passes from the liver to the gallbladder via the right and left hepatic ducts into the common hepatic duct
• The bile passes into the gallbladder via the cystic duct

58
Q

How does the gallbladder work

A

• Approx. 30 minutes after eating the gallbladder contracts - empties bile
• This forces bile through the cystic duct into the common bile duct
• The sphincter of Oddi relaxes
• Bile passes into the duodenum via the major duodenal papilla

59
Q

The pancreas

A

• Approx. 20cm long
• It has a head, neck, body and tail
• The head, neck and body are retroperitoneal
• The head sits in the curve of the duodenum, the tail touches the spleen
• The body sits behind the stomach

60
Q

Functions of the pancreas exocrine function

A

• Exocrine function
Has cells that secrete enzymes and alkaline pancreatic juices
These cause the gallbladder to contract and
release bile into the duodenum

61
Q

Endocrine function

A

• There is secretion of
Insulin – lowers blood glucose
Glucagon – raises blood glucose

62
Q

Regulation of blood glucose rising blood glucose level

A

Glucagon, a peptide hormone secreted by the pancreas, raises blood glucose levels. Its effect is opposite to insulin, which lowers blood glucose levels. When it reaches the liver, glucagon stimulates glycolysis, the breakdown of glycogen, and the export of glucose into the circulation.

63
Q

Regulation of blood glucose declining blood glucose level

A

low blood glucose level is detected by glucagon whoch releases cells of pancreas. glucagon releasing cells of pancreas are stimulated to release glucagon into the blood and to pass to the liver. liver breaks down glycogen stores and releases glucose to the blood. blood glucose level rises to set point which stimulates for glucagon release and body returns to homeostasis

Abdomen and Pelvis Anatomy and Pattern Recognition (1 decks)

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