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Anatomy 1 > 4) The Gastrointestinal System > Flashcards

4) The Gastrointestinal System Flashcards

1
Q

Where does the GI tract start and end?

A
  • The GI tract extends from the mouth to the anus
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2
Q

How can the GI tract be divided?

A
  • Embryonically: consisting of three separate sections: Upper (foregut), Middle (midgut) and Lower (hindgut)
  • GI bleed: consisting of upper GI and lower GI which is marked by the duodenojejunal junction (between the first two parts of the small intestine)
  • Endoscopy: consisting only of the upper GI tract (which is the oesophagus and stomach) and lower GI tract (which is the anus, rectum and colon)
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3
Q

What is the oral cavity?

A
  • The oral cavity is also known as the mouth and lies inferior to the nasal cavity
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4
Q

What are the different surfaces of the oral cavity?

A
  • The roof of the oral cavity consists of a hard palate (anteriorly) and a soft palate (posteriorly)
  • The floor consists of the tongue
  • The lateral walls are the cheeks
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5
Q

What are the different palates made from?

A
  • The hard palate is a bony structure

- The soft palate is made of muscular structures

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6
Q

What are the different arches of the oral cavity?

A
  • Posteriorly to the soft palate we find the palatoglossus muscle which forms the palatoglossal arch with a mucus lining
  • Even more posteriorly we find the palatopharyngeal arch
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7
Q

Where are the palatine tonsils found?

A
  • In between the palatoglossal arch and the palatopharyngeal arch we have the palatine tonsils
  • The palatine tonsil sits posterior to the tongue in the oropharynx
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8
Q

What is the uvula?

A
  • In the middle of the soft palate we have a uvula that hangs form the top.
  • It consists of soft tissue and is made from salivary glands.
  • It helps direct food towards the pharynx at the back
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9
Q

What is the posterior surface of the oral cavity?

A
  • The posterior surface (leading into the pharynx) is called the oropharyngeal isthmus.
  • It opens up into the pharynx and represents the border between the mouth and the pharynx.
  • It is marked by the palatoglossal arch
  • Closure of the oropharyngeal isthmus by the palatoglossus muscle will separate the oral cavity from the oropharynx
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10
Q

What is the epiglottis?

A
  • A leaf shaped cartilage which helps cover the laryngeal inlet and directs food from the oral cavity to the pharynx and into the oesophagus
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11
Q

What are the different papillae on the tongue?

A
  • Fungiform papillae: Found on the anterior part of the tongue
  • Filiform papillae: Densely packed at the central axis of the tongue but sparsely found in the peripheral regions
  • Vallate papillae: Form a V-shape structure towards the posterior of the tongue (found a 1/3rd of the way from the posterior part of the tongue to the anterior surface)
  • Foliate papillae: Found on the sides/margins of the tongue
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12
Q

What are the fungiform papillae?

A
  • They are found on the anterior part of the tongue

- They are round and relatively large

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13
Q

What are the filiform papillae?

A
  • Smalle cone-shaped mucosal projections

- They give a brushed appearance which are densely packed along the central axis

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14
Q

What are the vallate papillae?

A
  • Blunt ended, cylindrical papillae
  • They are the largest of all the papillae
  • There are about 8-12 of them that form a V-shape found closer to the posterior side of the tongue (about a 1/3rd of the way form the posterior to anterior of the tongue)
  • The innervation anterior to the vallate papillae are different than the innervations which are posterior
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15
Q

What are the Foliate papillae?

A
  • These are found on the sides of the tongue

- They are folds of mucosa and are sometimes described as leaf shaped papillae

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16
Q

What are the functions of the papillae?

A
  • They increase the contact between the tongue and the contents of the oral cavity
  • They all have taste buds on the surface apart from the filiform papillae
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17
Q

What is the pharynx?

A
  • A tube that joins the nasal cavity and oral cavity to the throat
  • It consists of the nasopharynx, oropharynx and laryngopharynx
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18
Q

What is the nasopharynx?

A
  • The region of the pharynx located at the start of the nasal cavity.
  • The opening of the pharyngotympanic tube marks the start of the nasopharynx and is the posterior entrance of the nasal cavity
  • Everything above the uvula is considered the nasopharynx
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19
Q

What is the oropharynx?

A
  • The region of the pharynx located behind the oral cavity
  • It sits in between the nasopharynx and laryngopharynx
  • It is marked by the two arches on the posterior side of the oral cavity. The superior arch is the uvula and the inferior arch is the epiglottis
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20
Q

What is the laryngopharynx?

A
  • The region of the pharynx leading into the oesophagus

- It starts at the epiglottis and ends at the oesophagus.

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21
Q

What is the function of the epiglottis?

A
  • The epiglottis gets pushed down to cover the laryngeal inlet (entrance to the larynx)
  • This allows food to be directed into the oesophagus
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22
Q

What is the relationship between the oesophagus and the trachea?

A
  • The oesophagus sits behind the trachea and the larynx
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23
Q

Why is the trachea always open?

A
  • The trachea is dilated as it is made of cartilages.

- It is the cartilaginous rings that keeps the trachea open

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24
Q

Why is the oesophagus constricted?

A
  • It is a muscular tube and as a result is collapsed
  • The oesophagus expands with the help of contractions of the trachealis muscle located on the anterior section of the oesophagus
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25
Q

What is the oesophagus?

A
  • It is a muscular tube that is subdivided into three parts (cervical, thoracic and abdominal)
  • It consists of three anatomical constrictions (cervical, thoracic and abdominal)
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26
Q

What are the three subdivisions of the oesophagus?

A
  • Cervical: Superior part of the oesophagus that is continuous with the oropharynx
  • Thoracic: Runs through the thorax from T1-T10. At T-10 it passes through the diaphragm at the muscular part (called the oesophageal hiatus)
  • Abdominal: Leads from the oesophageal hiatus into the cardia of the stomach (the first part of the stomach)
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27
Q

Why are there different constrictions within the oesophagus?

A

-These constrictions are caused by the position of the oesophagus in relation to other structures

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28
Q

What are the three constrictions of the oesophagus?

A
  • Cervical: Caused by the position of the cricoid cartilage as it has a broad piece of cartilage that constricts the oesophagus. It is found at C5/C6
  • Thoracic: Caused by the position of the aortic arch
  • Abdominal: Caused as it passes through the abdomen in the oesophageal hiatus
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29
Q

What is the peritoneum?

A
  • A thin, serous membrane lining of the abdominal and pelvic cavity
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30
Q

How is the peritoneum subdivided?

A
  • Parietal: Lines the walls of the abdominal and pelvic cavities
  • Visceral: Lines the organs/viscera
31
Q

What is the peritoneal cavity?

A
  • The space between the two layers of peritoneum
  • It is a potential space filled with serous fluid
  • It can accumulate this fluid during pathological conditions
32
Q

What is the relationship of the visceral and parietal peritoneum?

A
  • The visceral peritoneum is continuous with the parietal peritoneum
33
Q

What are intraperitoneal organs?

A
  • Organs that are completely covered in visceral peritoneum (e.g. stomach)
  • These organs are attached to each other or to the abdominal wall by peritoneal folds known as mesenteries
  • They are mobile so positioning can vary
34
Q

What are retroperitoneal organs?

A
  • Organs that lie behind the peritoneum and are only partially covered
  • These organs are not mobile (e.g. pancreas, duodenum and sigmoid colon) and so positioning cannot vary
35
Q

What are extraperitoneal elements?

A
  • Elements that lie outside of the peritoneum (e.g. fat and tissues)
36
Q

What is a mesentery?

A
  • A double layer of peritoneum that encloses an organ and usually connects it to the abdominal wall
  • Because they are double layered blood vessels (running down the posterior abdominal wall) pass in between the layers of the mesentery to reach their target organ
  • These vessels are protected by the mesentery
37
Q

What is the mesentery of the transverse colon called?

A
  • The transverse mesocolon
38
Q

What is an omentum?

A
  • Mesenteries associated with the stomach are often called omentums
  • They are a double-layered sheet or fold of peritoneum connecting two abdominal organs
  • The greater omentum hangs down like an apron and connects the stomach to the transverse colon. It contains variable amounts of fat and is mobile. It forms adhesion to areas of inflammation and limits spread of infection (by wrapping around the infection)
  • The lesser omentum connects the stomach to the liver
39
Q

How can we reach structures behind the stomach?

A
  • There is an opening known as the epiploic foramen from which we can pass instruments down to reach the space behind the stomach (called the lesser sac).
  • It is located just underneath the gall bladder and is an opening in the omentum
  • It allows us to reach any blood vessels that is located behind the stomach as well as any organs
40
Q

What is the greater and lesser sac?

A
  • Greater sac: Anything in front of the stomach

- Lesser sac: Anything behind the stomach

41
Q

What is a peritoneal ligament?

A
  • Mesenteries associated with the liver are often called ligaments
  • A thickened double layer of peritoneum that connects an organ with another organ or with the abdominal wall
42
Q

What is the falciform ligament?

A
  • A type of peritoneal ligament that connects the liver to the abdominal wall found on the anterior surface
  • It flows down all the way to the umbilicus (belly button) on the abdominal wall
  • During development it housed the umbilical vein which would bypass the liver and bring blood to the fetal heart.
  • However in adults it is a remnant of the umbilical vein
43
Q

What is the coronary ligament?

A
  • A type of peritoneal ligament that connects the liver to the underside of the diaphragm
  • The coronary ligament form a crown around the top of the liver
44
Q

What are the different parts of the stomach?

A
  • The stomach is continuous with the oesophagus and joins at the cardia of the stomach
  • Above this point is the fundus (the upper portion of the stomach) which is air filled
  • Below the cardia we find the body of the stomach where the contents of the stomach are passed down into
  • The stomach then narrows at the bottom called the pylorus
  • The first part of the pylorus is the pyloric antrum and the second part is called the pyloric canal
  • At the end of the pylorus we find a sphincter that controls release of the stomach contents into the duodenum of the small intestines
45
Q

What are the different curvatures of the stomach?

A
  • We have a lesser curvature (on the side that contains the cardia/ the right side) and a greater curvature (on the left side of the stomach)
  • The lesser omentum is attached to the lesser curvature and the greater omentum is attached to the greater curvature
46
Q

What is the rugae of the stomach?

A
  • The inner surface of the stomach consists of muscular folds called gastric rugae (rugae of the stomach)
  • The rugae help increase surface area and allow opportunity for expansion when the stomach is full
47
Q

What happens at the duodenum?

A
  • The beginning duodenum is attached to the lesser omentum and so is mobile.
  • However the rest of the duodenum becomes retroperitoneal and disappears behind other structures and organs
48
Q

What is the liver?

A
  • It is the largest gland in the body that sits on the dome of the diaphragm which is located anteriorly
  • Since the right lobe is larger than the left lobe it causes the right dome of the diaphragm to sit higher than the left dome
  • It is a soft, pliable organ that should not be palpable as it lies under the cover of the right coastal margin
  • However upon taking a deep breathe, the diaphragm will contract which will push down on the liver allowing it to be palpable
  • The indentations on the visceral (back) surface are due to organs sitting behind the liver
49
Q

What are the functions of the liver?

A
  • Production and secretion of bile
  • Metabolism of carbohydrates, fats and proteins
  • Filtration of blood to remove bacteria and foreign particles that gain entrance to the blood from the small intestines
  • Synthesis of heparin which is an anticoagulant with important detoxification functions
50
Q

What are the different structures of the liver?

A
  • The liver consists of a right lobe (which is bigger) and a left lobe (which is smaller)
  • There is a quadrate (square shaped) lobe which is formed between the gall bladder and the falciform ligament
  • Superior to the quadrate lobe is hepatic artery, the beginning of the bile duct and portal vein
  • Above the quadrate lobe we also find a caudate lobe which is formed to the left of the inferior vena cava
  • We also find the falciform ligament
  • There is a porta hepatis which is a gateway into and out of the liver and is where the three vessels (artery, vein and bile duct) flow through
  • There is a gall bladder that stores and concentrate the bile made by the liver
51
Q

What is the bare area of the liver?

A
  • The liver is an intraperitoneal organ as it is almost fully covered in peritoneum
  • However at the top it bursts out of the peritoneum as it has grown too large during developments
  • This area is not covered in peritoneum and is called the bare area
  • The bare area is surrounded by the coronary ligaments
  • It is the bare area that comes in contact with the diaphragm
52
Q

What are the different parts of the gall bladder?

A
  • Fundus (most inferior part) which sticks out just below the liver and can be seen from a posterior view
  • Body that is located above the fundus
  • Neck which is the most superior part
  • The neck is continuous with the cystic duct which is how bile flows out of the gall bladder
  • The cystic duct joins together with the left and right hepatic duct (which brings bile from the liver) to form the bile duct
53
Q

How does the gall bladder secrete bile?

A
  • The gall bladder narrows from its body up to the neck which secretes bile into the cystic duct
  • From here the cystic duct joins with the left and right hepatic ducts to form the bile duct which passes down and empties into the duodenum
54
Q

What do the different vessels in the porta hepatis do?

A
  • Bile duct carries bile that has come from the liver and gall bladder
  • The portal vein brings venous blood from the small intestines
  • Hepatic artery brings arterial blood from the aorta to the liver
55
Q

Describe the positioning of the pancreas.

A
  • The pancreas sits behind the duodenum
  • It consists of a head, a body and a tail
  • The head is found just to the right of the midline while the body passes over the midline to the left side of the body where it eventually becomes the tail
56
Q

What is the duodenum?

A
  • The duodenum is a C-shaped structure that marks the start of the small intestines and is found in front of the pancreas.
  • The interior surface consists of circular folds called plicae circulares
  • There is also an opening where the bile duct and pancreas empties into the duodenum which is called the major duodenal papilla
  • The duodenojejunal junction is the part where the duodenum leads into the jejunum
57
Q

How are the jejunum and ileum held in place?

A
  • The jejunum and ileum make up the majority of the small intestines
  • They are really large so are folded and are attached to the posterior abdominal wall by mesenteries
  • The mesenteries have a short length but fans out to join to a large length of small intestine
58
Q

What is the jejunum?

A
  • The jejunum makes up the proximal 2/5ths of the small intestine (closer to the duodenum)
  • The jejunum continues on from the duodenum and leads into the ileum
  • The jejunum has a wider lumen and is thick walled
  • It has denser and more prominent plicae circulares
  • There are fewer arterial arcades and long vasa recta (arteries leading to the small intestine)
  • Their mesenteries also contain less fat
59
Q

What is the ileum?

A
  • The ileum makes up the distal 3/5ths of the small intestine (further from the duodenum)
  • The ileum continues on from the jejunum and leads onto the large intestines
  • At the end of the ileum we find the ileocecal junction where the small intestines terminate and we lead into the large intestines
  • It has a much more narrow lumen that is thin walled
  • It has sparse or absent plicae circulares
  • There are more arterial arcades (arches) and short vasa recta
  • Their mesenteries contain more fat
60
Q

How are the jejunum and ileum perfused?

A
  • The main artery and vein suppling this part of the small intestines runs along the posterior abdominal wall
  • Their branches fan out in between the layers of the mesentery. These branches are known as vasa recta
61
Q

What are the different parts of the large intestine?

A
  • The ileocecal junction marks the start of the large intestines and is continuous with the caecum which is the first part of the large intestines
  • At the base of the caecum we find the appendix and is mobile as it is attached to the large intestine via the mesoappendix. Because it is mobile positioning can vary
  • The caecum leads into the ascending colon (found on the right side of the body)
  • The ascending colon hits the liver and bends to become the transverse colon (going across the midline of the body)
  • The transverse colon hits the spleen on the left side of the body and bends down to become the descending colon
  • The descending colon then becomes S-shaped as it reaches the bottom where it is called the Sigmoid colon
  • The sigmoid colon then leads to the rectum which then leads into the anal canal
62
Q

What are special features of the large intestines?

A
  • Taeniae coli is a longitudinal band of muscle that runs along the external surface
  • When the taeniae coli contract they form the folds in the large intestine that we see (called the haustra)
  • Appendices epiploicae are also found which are fatty deposits on the external surface
63
Q

Why is the contraction of taenia coli important?

A
  • It helps move the bowel contents through the bowel
64
Q

How is the rectum and anal canal orientated in females?

A
  • In females the bladder sits in front of the female reproductive tract
  • Behind the reproductive tract we find the anal canal which sits along the back of the pelvic wall as they follow the curvature of the spine
65
Q

How is the rectum and anal canal orientated in males?

A
  • In males the bladder sits anterior and the anal canal sits posterior with no reproductive tract in between
  • Around the neck of the bladder we find the prostate
66
Q

What are the different subdivisions of the GI tract?

A
  • Foregut: From part of the oesophagus till the start of the duodenum. It also contains accessory organs such as gall bladder, liver, parts of the pancreas and spleen
  • Midgut: The rest of the duodenum till the end of the ascending colon
  • Hindgut: The transverse colon till the anus
67
Q

What vessels perfuse the different parts of the GI tract?

A
  • Foregut: Coeliac trunk
  • Midgut: Superior mesenteric artery
  • Hindgut: Inferior mesenteric artery

(These arteries are all branches of the abdominal aorta)

68
Q

What are the different branches of the coeliac trunk?

A

(The coeliac trunk is very tiny and quickly divides into three branches. It sits at T-12)

  • Hepatic artery: Goes to the liver and proximal duodenum
  • Splenic artery: Goes to the spleen (on top of the pancreas) that is quite bendy. It also supplies the pancreas
  • Left gastric artery: Goes to the stomach
69
Q

How are the intestines perfused?

A
  • The small intestines and a large part of the large intestine (the midgut) is supplied by the superior mesenteric artery
  • It passes along the root of the mesentery and branches out in the mesentery to supply the small intestines and follows along the ascending and transverse colon
  • The remainder of the large intestines and the rectum (the hindgut) are supplied by the inferior mesenteric artery
  • The superior and inferior mesenteric arteries anastomose around the border of the colon.
  • This anastomosis means there is an alternative pathway for blood to reach a target organ/region if there is a blockage
70
Q

How does venous drainage in the GI tract occur?

A
  • Venous blood from the greater part of the GI tract and accessory organs are drained to the liver by the ‘portal venous system’
  • The portal veins are formed when the superior mesenteric and splenic veins join together behind the neck of the pancreas
  • The portal vein enters the liver and breaks up into the sinusoids, from which blood passes into the hepatic veins that joins the inferior vena cava
71
Q

Why does the body need a portal venous system?

A
  • The portal venous system is different from the systemic venous system
  • This is because blood from the GI tract has to pass through the liver so that the products of digestion can be metabolised and stored before it reaches the heart.
  • Furthermore this blood needs to also be filtered of any drugs
72
Q

How does communication occur between the central venous system and the portal venous system?

A
  • This communication takes place through portal-systemic anastomoses.
  • These are found in the oesophagus, rectum, paraumbilical (around the umbilical region) and in the colon
  • These communications are important as they provide an alternate pathway for blood in case the direct route to the target region is blocked
73
Q

What are varices and how do they form?

A
  • Varices are swelling of the veins
  • When a person suffers from liver disease the veins can get blocked and so causes blood to be directed elsewhere into tiny veins
  • This causes varices/swelling of veins due to the amount of blood directed into them
  • These varices can further lead to haemorrhoids

Anatomy 1 (8 decks)

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