Anatomy

Question 1

How is the The abdominal cavity separated from the thorax?

Answer 1

By the diaphragm

Question 2

Apertures

Answer 2

the diaphragm contains apertures that allow structures to pass between the thorax and abdomen.

The pelvic cavity lies inferior to the abdominal cavity and is continuous with it.

Question 3

What organs does the abdominal cavity contain?

Answer 3

Organs of the

gastrointestinal tract (stomach, small and large intestine),

the hepatobiliary system (liver and gallbladder),

the urinary system (kidneys and ureters)

the endocrine system (pancreas and adrenal glands)

The abdomen also contains the spleen (a haematopoietic and lymphoid organ) and the great vessels (abdominal aorta and inferior vena cava) and their branches.

Question 4

What are the anterior, lateral and posterior walls of the abdomen composed of?

Answer 4

skin, subcutaneous tissue and muscles and their associated aponeuroses (flat tendons).

Five lumbar vertebrae contribute to the posterior wall of the abdominal cavit

Question 5

Functions of the abdominal wall

Answer 5

• protect the abdominal viscera

• increase intra-abdominal pressure (e.g. for defecation and childbirth)

• maintain posture and move the trunk

Question 6

parietal peritoneum

Answer 6

Serous membrane lining the internal aspect of the abdominal walls

Question 7

Several bony landmarks define the boundaries of the abdominal cavity. These are the:

Answer 7

• Xiphisternum
• Costal margin
• Iliac crests
• Anterior superior iliac spines (ASIS)
• Pubic tubercles
• Pubic symphysis (a fibrocartilaginous joint)

Question 8

The 4 quadrants

Answer 8

a vertical line that runs down the midline through the lower sternum, umbilicus, and the pubic symphysis

• a horizontal line that runs across the abdomen through the umbilicus.

Question 9

The 9 regions- The abdomen is divided into nine regions by four imaginary lines:

Answer 9

the right and left midclavicular lines, which extend vertically from the midclavicular point to the mid-inguinal point (halfway between the anterior superior iliac spine and the pubic tubercle)

• the subcostal line - a horizontal line drawn through the inferior-most parts of the right and left costal margins (through the 10th costal cartilage)

• the intertubercular line - a horizontal line drawn through the tubercles of the right and left iliac crests and the body of L5.

Question 10

In addition to the subcostal and intertubercular planes described above, other landmarks and planes associated with the abdominal wall

Answer 10

Transpyloric plane

Transumbilical plane

Intercristal plane

McBurney’s point

Question 11

Transpyloric plane

Answer 11

a horizontal line that passes through the tips of the right and left ninth costal cartilages.

It lies between the superior border of the manubrium and the pubic symphysis.

It transects the pylorus of the stomach, the gallbladder, the pancreas and the hila of the kidneys.

Question 12

Transumbilical plane

Answer 12

this is an unreliable landmark as its position varies depending on the amount of subcutaneous fat present.

In a slender individual it lies approximately at the level of L3.

Question 13

Intercristal plane

Answer 13

a horizontal line drawn between the highest points of the right and left iliac crests.

It cannot be palpated from the anterior aspect of the abdominal wall. It is used to guide procedures on the back (e.g. lumbar puncture).

Question 14

McBurney’s point

Answer 14

the surface marking of the base of the appendix.

It lies two thirds of the way along a line drawn from the umbilicus to the right anterior superior iliac spine.

Question 15

4 pairs of muscles comprise the anterolateral abdominal wall

Answer 15

External oblique

Internal oblique

Transversus abdominis (horizontally orientated fibres)

Recuts abdominis (rectus=straight)

Question 16

Where can the rectus abdominis muscles be found?

Answer 16

The vertical right and left rectus abdominis muscles lie either side of the midline.

Rectus abdominis is attached to the sternum and costal margin superiorly and to the pubis inferiorly and is surrounded by an aponeurotic rectus sheath

Question 17

Lateral to the rectus abdominis lie three sheets of muscle whose fibres run in different directions to each other:

Answer 17

• External oblique (EO) is most superficial. The fibres of EO run medially and inferiorly, towards the midline

• Internal oblique (IO) lies deep to EO. The fibres of IO are orientated perpendicular to those of EO (they run medially and superiorly).

• Transversus abdominis lies deep to internal oblique. Its fibres are orientated horizontally.

Question 18

Anteriorly, these muscles become aponeurotic (an aponeurosis is a flat tendon)

Answer 18

The fibres of the aponeuroses fuse with each other and, in the midline, they fuse with the aponeuroses of the opposite side, forming a tough midline raphe (= seam) called the linea alba (‘white line’).

The aponeuroses of these muscles also form the rectus sheath, which encloses the rectus abdominis.

Question 19

The right and left rectus abdominis muscles lie either side of the linea alba.

Answer 19

• It is comprised of muscle segments interspersed with horizontal tendinous bands

When the muscle segments hypertrophy with exercise, they bulge either side of the tendinous bands and can been seen on the anterior abdominal wall as bulges – the ‘six-pack’.

Question 20

Rectus abdominis lies within the rectus sheath.

The anterior and posterior walls of the rectus sheath are formed by the aponeuroses of EO, IO and transversus abdominis

Answer 20

• As it approaches the midline, the aponeurosis of IO splits into anterior and posterior layers

• The EO aponeurosis and the anterior layer of the IO aponeurosis form the anterior wall of the rectus sheath

• The posterior layer of the IO aponeurosis and the transversus abdominis aponeurosis form the posterior wall of the rectus sheath.

Question 21

The transversalis fascia lies deep to transversus abdominis

Answer 21

Deep to the fascia lies the parietal peritoneum

Question 22

The most inferior part of the external oblique aponeurosis is attached to the anterior superior iliac spine laterally and the pubic tubercle medially, forming the inguinal ligament

Answer 22

Just above the inguinal ligament is the inguinal canal

Question 23

Vessels of the Anterior Abdominal Wall- The anterolateral abdominal wall is supplied by the following arteries:

Answer 23

• musculophrenic artery, a branch of the internal thoracic

• superior epigastric artery, which is the continuation of the internal thoracic artery. It descends in the rectus sheath

• inferior epigastric artery, a branch of the external iliac artery. It ascends in the rectus sheath and anastomoses with the superior epigastric

These vessels are accompanied by deep veins.
An extensive network of superficial veins is found in the anterolateral abdominal wall

Question 24

The muscles and skin of the anterolateral abdominal wall are innervated by:

Answer 24

• Thoraco-abdominal nerves T7 – T11. These are essentially the continuation of the intercostal nerves T7 – T11. These somatic nerves contain sensory and motor fibres

• The subcostal nerve – this originates from the T12 spinal nerve (so called because it runs along the inferior border of the 12th rib)

• Iliohypogastric and ilioinguinal nerves – both are branches of the L1 spinal nerve

Question 25

Parietal peritoneum lines the abdominal wall

Answer 25

• It can be seen with naked eye and is innervated by the somatic nerves that supply the overlying muscles and skin of the abdominal wall

• Pain from the parietal peritoneum is usually sharp, severe, and well localised to the abdominal wall

Question 26

Visceral peritoneum covers the abdominal viscera

Answer 26

• It is adhered to the surface of the viscera and cannot be seen with the naked eye

• The visceral peritoneum is innervated by visceral sensory nerves. These nerves convey ‘painful’ sensations back to the CNS along the path of the sympathetic nerves that innervate the organ / structure it covers

• Pain from the visceral peritoneum can be severe. It is usually dull and diffuse (i.e. it cannot be pinpointed to a specific location)

• ‘Painful’ sensations from the visceral peritoneum may be perceived as nausea or distension

Question 27

Peritoneal cavity

Answer 27

Between the parietal and visceral peritoneum lies the peritoneal cavity

In a healthy abdomen, a thin film of peritoneal fluid lies in the peritoneal cavity

It allows the viscera to slide freely alongside each other

The two layers of peritoneum are continuous with each other. The arrangement of the two layers mirrors the arrangement of the parietal and visceral pleurae

Question 28

Depending on the extent to which they are covered by peritoneum, the abdominal viscera are described as:

Answer 28

• Intraperitoneal: almost completely covered by peritoneum e.g. the stomach

• Retroperitoneal: posterior to the peritoneum, hence only covered by peritoneum on their anterior surface e.g. the pancreas and abdominal aorta.

Question 29

Mesenteries, Omenta, Ligaments and Folds

Answer 29

• They are all composed of peritoneum and connect organs to each other and to the abdominal wall

• They may carry blood vessels, nerves, and lymphatics to the viscera

• They contain a variable amount of fat; some are usually very fatty (the omenta).

Question 30

Mesenteries

Answer 30

are folds of peritoneum that contain fat and suspend the small intestine and parts of the large intestine from the posterior abdominal wall

Arteries that supply the intestine (from the abdominal aorta) and veins that drain the gut (tributaries of the portal venous system) are embedded in the mesenteries.

Question 31

The greater and lesser omertà

Answer 31

folds of peritoneum that are usually fatty and connect the stomach to other organs

Question 32

The greater omentum

Answer 32

Hangs from the greater curvature of the stomach and lies superficial to the small intestine

Question 33

The lesser omentum

Answer 33

connects the stomach and duodenum (the first part of the
small intestine) to the liver

The hepatic artery, the hepatic portal vein, and the bile duct (the ‘portal triad’) are embedded within its free edge.

Question 34

Ligaments

Answer 34

Are folds of peritoneum that connect organs to each other or to the abdominal wall.

Question 35

Peritoneal ligaments

Answer 35

falciform ligament, which connects the anterior surface of the liver to the anterior abdominal wall

the coronary and triangular ligaments, which connect the superior surface of the liver to the diaphragm

Question 36

Where are peritoneal folds raised from?

Answer 36

Raised from the internal aspect of the lower abdominal wall and are created by the structures they overlie, like carpet running over a cable

Question 37

Where does the median umbilical fold lie?

Answer 37

lies in the midline and represents the remnant of the urachus, an embryological structure that connected the bladder to the umbilicus.

Question 38

Lateral to the median umbilical fold lie the medial umbilical folds

Answer 38

These represent the remnants of the paired umbilical arteries, which returned venous blood to the placenta in foetal life

Question 39

Lateral to the medial umbilical folds are the lateral umbilical folds

Answer 39

The inferior epigastric arteries lie deep to these peritoneal folds. They supply the anterior abdominal wall

Question 40

The peritoneal cavity is divided into two regions of unequal size

Answer 40

• The smaller lesser sac (also called the omental bursa) is a space that lies posterior to the stomach and anterior to the pancreas

• The larger greater sac is the remaining part of the peritoneal cavity.

Question 41

How do the greater and lesser sacs communicate with each other?

Answer 41

via a passageway that lies posterior to the free edge of the lesser omentum, the epiploic foramen (also called the omental foramen)

Question 42

Where does the gastrointestinal system develop from

Answer 42

The gastrointestinal system develops from the embryonic gut tube which lies in the midline of the abdominal cavity, suspended from the posterior abdominal wall by the dorsal mesentery

Question 43

Major branches of the abdominal aorta that supply the developing gut tube travel through the dorsal mesentery

Answer 43

The ventral mesentery connects the stomach to the anterior abdominal wall

As the liver grows within it, the anterior part of the ventral mesentery becomes the falciform ligament and the posterior part becomes the lesser omentum

Question 44

During development, organs grow, migrate, and rotate towards their final positions

Answer 44

As they do so, they ‘pull’ their peritoneal attachments with them.

Growth, migration, and rotation of organs during development is responsible for the formation of the lesser sac and results in some organs being ‘pushed’ onto the posterior abdominal wall and becoming retroperitoneal

Question 45

Distal oesophagus

Answer 45

The oesophagus passes through the oesophageal hiatus in the diaphragm at the level of T10.

The muscle around the hiatus functions as a sphincter that prevents reflux of stomach contents into the oesophagus.

The abdominal segment of the oesophagus is less than 2 centimetres long.

Question 46

What is the distal oesophagus supplied by?

Answer 46

branches from the left gastric artery.

Its venous drainage is towards both the systemic system of veins (via oesophageal veins that drain into the azygos vein) and to the portal venous system (via the left gastric veins).

The distal oesophagus is thus a site of portosystemic anastomoses, which are clinically important.

Question 47

Shape of the stomach

Answer 47

The stomach is a J-shaped sac that expands to accommodate food and fluid.

The stomach chemically and mechanically breaks down food into chyme

Question 48

The stomach is described in 4 parts

Answer 48

• The oesophagus travels through the diaphragm at the level of T10 and is continuous with the cardia of the stomach

• The most superior part of the stomach is the fundus. It lies superior to the level of entry of the oesophagus and is usually filled with gas

• The largest part of the stomach is the body

• The pyloric part is distal to the body. The pyloric antrum is wide and tapers towards the pyloric canal, which is narrow and contains the pyloric sphincter The sphincter is a formed of circular smooth muscle. It regulates the passage of chyme into the duodenum

• The right border of the stomach is the lesser curvature. The longer left border is the greater curvature

Question 49

Location and relations of the stomach and the lesser sac

Answer 49

The stomach lies in the left upper quadrant, but its size and position are variable. It is covered with visceral peritoneum

Question 50

Its anterior surface is related to the anterior abdominal wall, diaphragm, and left
lobe of the liver

Answer 50

Its posterior surface forms the anterior wall of the lesser sac

Question 51

The lesser sac and the structures that form its posterior wall lie posterior to the stomach: these include the pancreas, left kidney and spleen.

Answer 51

The lesser omentum connects the lesser curvature to the liver

Question 52

The free edge of the lesser omentum contains the hepatic artery, hepatic portal
vein and the bile duct.

Answer 52

Posterior to the free edge is the entrance to the lesser sac.

The greater omentum hangs from the greater curvature

Question 53

Blood supply of the stomach

Answer 53

The stomach is supplied by arteries that branch from the coeliac trunk.

The coeliac trunk is one of three large unpaired vessels that leave the anterior aspect of the abdominal aorta (at the level of T12) to supply the abdominal viscera that are derived from the embryological foregut.

Question 54

The foregut comprises the stomach, the first half of the duodenum, the liver, gallbladder, and pancreas

Answer 54

The spleen develops in the dorsal mesentery, and is supplied by the coeliac trunk, but it is mesodermal in origin

Question 55

The coeliac trunk is only a short stump; it divides into three branches close to the aorta

Answer 55

These are the left gastric artery, the common hepatic artery, and the splenic artery

The left gastric is a much smaller calibre vessel than the common hepatic and splenic arteries

Question 56

The left and right gastric arteries run along the lesser curvature of the stomach and anastomose with each other.

Answer 56

• The left gastric artery arises from the coeliac trunk

• The right gastric artery usually arises from the common hepatic artery

Question 57

The left and right gastro-omental (gastroepiploic) arteries run along the greater curvature of the stomach and anastomose with each other

Answer 57

• The left gastro-omental artery arises from the splenic artery

• The right gastro-omental artery arises from the gastroduodenal artery, a branch of the common hepatic artery

Question 58

Right and left gastric veins and right and left gastro-omental veins accompany the arteries described above.

They ultimately drain into the hepatic portal vein (HPV).

Answer 58

The hepatic portal vein is a large vein that carries nutrient-rich venous blood from the GI tract to the liver

Question 59

Innervation of the stomach

Answer 59

The vagus nerve conveys parasympathetic fibres to the stomach.

Parasympathetic stimulation promotes peristalsis and gastric secretion

Sympathetic fibres are conveyed to the stomach via the greater splanchnic nerve.

The greater splanchnic nerve is formed of preganglionic sympathetic fibres that leave spinal cord segments T5-T9 and pass through the sympathetic trunk without synapsing.
The fibres synapse in prevertebral ganglia around the coeliac trunk. The postganglionic fibres travel to the stomach and inhibit peristalsis and secretion.

Question 60

Small intestine

Answer 60

The small intestine lies centrally in the abdomen and has three ‘parts’ that are continuous with each other; the duodenum, the jejunum, and the ileum

Question 61

Duodenum

Answer 61

The duodenum is continuous with the pylorus of the stomach

It is short and curved into a C-shape around the head of the pancreas. Most of the length of the duodenum is retroperitoneal

Question 62

Approximately halfway along the internal wall of the duodenum is the major duodenal papilla

Answer 62

This is the opening of the bile duct and the main pancreatic duct into the duodenum

Question 63

Where does each part of the duodenum develop from?

Answer 63

The first half of the duodenum develops from the embryological foregut and is supplied by arterial branches from the coeliac trunk.

The second half of the duodenum develops from the embryological midgut and is supplied by branches from the artery of the midgut – the superior mesenteric artery.

Question 64

Jejunum and Ileum

Answer 64

The jejunum is continuous with the duodenum

Both the jejunum and ileum are intraperitoneal and are ‘suspended’ from the posterior abdominal wall by the mesentery of the small intestine

Question 65

Blood vessels that supply the small intestine (from the superior mesenteric artery) are embedded within the mesentery

Answer 65

The small intestine lies centrally in the abdomen; the jejunum lying in the left upper region and the ileum lying in the right lower region

Question 66

Where are the jejunum and ileum derived from?

Answer 66

Both the jejunum and ileum are derived from the embryological midgut

Question 67

Structure of the jejunum and ileum

Answer 67

The jejunum and ileum are the sites of nutrient absorption, so have a vast surface area: the small intestine is long, the mucosa is folded (plicae circulares), the mucosal folds bear villi and there are microvilli on the luminal surface of each epithelial cell.

Question 68

Internal difference between the jejunum and the ileum

Answer 68

The plicae are more pronounced in the jejunum. The internal ileum is characterised by Peyer’s patches, which are large submucosal lymph nodules.

Question 69

Meckel’s diverticulum

Answer 69

In some people, the ileum bears a blind-ended diverticulum approximately one meter from its termination; meckels diverticulum

It is the embryological remnant of the connection that was present between the midgut loop to the yolk sac. If it becomes inflamed, it may mimic an appendicitis (inflammation of the appendix)

Question 70

The terminal ileum

Answer 70

The terminal ileum is continuous with the caecum - the first part of the large intestine – at the ileocaecal junction in the right iliac fossa.

Question 71

The large intestine function

Answer 71

reabsorbs water from faecal material to form semi-solid faeces. It lies peripherally in the abdomen and is composed of the caecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal

Question 72

Segments of the large intestine

Answer 72

Some segments are retroperitoneal, and some are intraperitoneal

Question 73

Distinguishing between the large and small intestine

Answer 73

The large intestine is peripherally located, and larger calibre.
The outer longitudinal muscle layer is organised into three bands – the taeniae coli

The inner circular muscle layer forms ‘bulges’ called haustra (or haustrations).

The large intestine bears fatty tags called epiploic appendages (appendices epiploicae) that mark the point at which blood vessels penetrate the intestinal wall.

Question 74

Caecum

Answer 74

The caecum is the first part of the large intestine. It is a distended (swollen), blind-ended ‘pouch’.

The caecum is covered by peritoneum but does not have a mesentery.

Question 75

Appendix

Answer 75

The appendix is a small diverticulum that arises from the caecum and contains lymphoid tissue.

The surface marking of the base of the appendix is McBurney’s point.

The appendix varies in length and the position of its tip is variable. The appendix is connected to the caecum by a small mesentery, the mesoappendix.

Question 76

Ascending colon

Answer 76

The ascending colon is continuous with the caecum. It runs vertically on the right side of the posterior abdominal wall in the right paracolic gutter. It is retroperitoneal (it is an example of a secondarily retroperitoneal organ).

The ascending colon makes a 90 degree turn left in the right upper quadrant, becoming continuous with the transverse colon.

The ‘bend’ in the colon here is the hepatic flexure (sometimes called the right colic flexure).

Question 77

Transverse colon

Answer 77

The transverse colon is continuous with the ascending colon. It runs horizontally in the upper abdomen but often hangs inferiorly. It is intraperitoneal and is suspended from the posterior abdominal wall by the transverse mesocolon.

The transverse colon makes a 90 degree turn inferiorly in the left upper quadrant, becoming continuous with the descending colon. The ‘bend’ in the colon here is the splenic flexure (sometimes called the left colic flexure).

The splenic flexure is tethered to the diaphragm by the phrenicocolic ligament

Question 78

The transverse colon marks the transition point between the embryological midgut and embryological hindgut

Answer 78

The proximal (first) two thirds develop from the embryological midgut, whilst the distal (last) third develops from the embryological hindgut.

This means that these two parts of the transverse colon are supplied by different blood vessels and nerve

Question 79

Descending colon

Answer 79

The descending colon is continuous with the transverse colon superiorly and the sigmoid colon inferiorly.

It runs vertically on the left side of the posterior abdominal wall in the left paracolic gutter. It is retroperitoneal (also secondarily retroperitoneal).

Question 80

Sigmoid colon

Answer 80

The sigmoid colon lies in the left lower quadrant and is named because of its sinuous shape.

It is continuous with the descending colon superiorly and the rectum inferiorly.

As the sigmoid approaches the midline, it makes a 90 degree turn inferiorly into the pelvis - this ‘bend’ is the rectosigmoid junction.

The sigmoid colon has a mesentery - the sigmoid mesocolon - and is therefore intraperitoneal.

Question 81

Rectum and anal canal

Answer 81

The rectum descends inferiorly into the pelvis from the rectosigmoid junction and is retroperitoneal.

The rectum stores feaces until it is convenient to defecate.

The rectum is continuous inferiorly with the anal canal.

Question 82

The gastrointestinal tract is supplied by three large unpaired arteries that leave the abdominal aorta. These are the:

Answer 82

• coeliac trunk
• superior mesenteric artery (SMA)
• inferior mesenteric artery (IMA)

Question 83

Coeliac trunk

Answer 83

It leaves the aorta at the level of T12 and gives rise to branches that supply the foregut – the oesophagus, stomach, first half of the duodenum, liver, gallbladder, bile ducts, pancreas and spleen.

Question 84

The superior mesenteric is the artery of the midgut

Answer 84

It leaves the aorta at the level of L1.

Its branches supply the midgut structures: the second half of the duodenum, the small intestine, and the large intestine as far as (and including) the first two thirds of the transverse colon.

Branches also supply parts of the pancreas.

Question 85

The inferior mesenteric artery is the artery of the hindgut

Answer 85

It leaves the aorta at the level of L3. It is a smaller calibre vessel than the coeliac trunk and SMA.

Its branches supply the hindgut structures: the distal third of the transverse colon, the descending and sigmoid colon, the rectum, and the upper part of the anal canal.

Question 86

The superior mesenteric artery

Answer 86

gives rise to several major branches that supply the midgut, but it is important to bear in mind that these vessels form extensive anastomoses with each other

Question 87

Major branches are:

Answer 87

• Jejunal branches – several branches to the jejunum
• Ileal branches – several branches to the ileum
• Ileocolic artery – supplies the caecum, appendix, and ascending colon
• Right colic artery – supplies the ascending colon
• Middle colic artery – supplies the transverse colon.

Question 88

The jejunal and ileal branches are embedded in the mesentery of the small intestine.

Answer 88

They anastomose with each other, forming ‘loops’ of arteries called arcades.

From these arcades run the vasa recta (‘straight’ vessels), which supply the intestinal wall.

Question 89

The inferior mesenteries artery

Answer 89

gives rise to several major branches that supply the hindgut

Question 90

Major branches are:

Answer 90

• Left colic artery – supplies the transverse colon and the descending colon
• Sigmoid branches – supply the sigmoid colon
• Superior rectal artery – the terminal branch of the IMA, which supplies the upper
rectum.

Question 91

Branches of the middle colic artery (from the SMA) and left colic artery anastomose along the distal third of the transverse colon and the splenic flexure forming the marginal artery

Answer 91

Branches of the left colic and sigmoid arteries anastomose

The lower rectum is supplied by blood vessels that originate from the internal iliac arteries in the pelvis.

Question 92

Venous blood from the gut ultimately reaches the inferior vena cava (IVC) and is returned to the heart.

Answer 92

However, venous blood from the gut contains absorbed nutrients, so it first enters the liver via the portal venous system before being returned to the heart via the IVC

Question 93

The inferior mesenteric vein (IMV) accompanies the IMA and drains the hindgut.

The inferior mesenteric vein ascends on the left side of the abdomen and typically drains into the splenic vein from the spleen.

Answer 93

The superior mesenteric vein (SMV) accompanies the SMA and drains the midgut.

The SMV ascends and unites with the splenic vein close to the liver (posterior to the neck of the pancreas) to form the hepatic portal vein.

Question 94

The hepatic portal vein enters the liver

Answer 94

After the nutrients are removed from the blood, it enters small hepatic veins, which unite within the liver to form two or three large hepatic veins that enter the IVC as it passes posterior the liver (hence the hepatic veins are within the liver and cannot be seen externally)

Question 95

The midgut and hindgut are innervated by parasympathetic fibres that stimulate peristalsis and secretions

Answer 95

However, parasympathetic fibres travel to the midgut and hindgut via different nerves

Question 96

The foregut and midgut (i.e. as far as two thirds of the way along the transverse colon)

Answer 96

are innervated with parasympathetic fibres via the vagus nerve

Question 97

The hindgut (the last third of the transverse colon as far distally as the upper anal canal)

Answer 97

is innervated with parasympathetic fibres via the pelvic splanchnic nerves.

These nerves are formed by the axons of parasympathetic neurons that lie in the sacral spinal cord

Question 98

The cell bodies of preganglionic parasympathetic neurons lie in sacral segments S2 – S4

Answer 98

The axons of these neurons leave the spinal cord and form the pelvic splanchnic nerves

The preganglionic axons synapse with a second neuron in a ganglion.
The parasympathetic ganglia are located very close to, or even within, the walls of the viscera

The pelvic splanchnic nerves also convey parasympathetic fibres to the pelvic viscera

Question 99

Preganglionic sympathetic fibres from T5 – T12 pass through the sympathetic trunk (without synapsing) via the greater, lesser, and least splanchnic nerves.

Answer 99

• The greater splanchnic carries fibres from T5 – T9 and innervates the foregut.

• The lesser splanchnic carries fibres from T10 – T11 and innervates the midgut.

• The least splanchnic carries fibres from T12 and innervates the hindgut.

Question 100

The preganglionic fibres in these nerves synapse within in ganglia that lie in the abdomen, clustered around the aorta and the coeliac trunk, SMA and IMA

Answer 100

The postganglionic sympathetic fibres form visceral nerves that innervate the gut

These fibres that inhibit peristalsis and secretions

Question 101

The sympathetic fibres are visceral motor fibres

Answer 101

The gut is also innervated by visceral sensory fibres which convey visceral sensory information from the gut to the CNS

Such information usually does not reach consciousness, but painful sensations caused by ischaemia, distension or spasm do reach our conscious perception

Question 102

Visceral sensory fibres from the foregut, midgut, and hindgut travel to the CNS alongside the sympathetic fibres that innervate that part of the gut, hence painful sensations from the:

Answer 102

• foregut enter spinal cord segments T5 - T9

• midgut enter spinal cord segments T10 – T11

• hindgut enter spinal cord segment T12

Question 103

These regions of the spinal cord also receive somatic sensory information from the abdominal wall

Answer 103

• Segments T5 – T9 receive information from dermatomes T5 – T9 (upper abdomen and epigastrium)

• Segments T10 – T11 receive information from dermatomes T10 – T11 (the umbilical region)

• Segment T12 receives information from dermatome T12 (the suprapubic region)

Question 104

Pain from the abdominal viscera is referred to the body wall:

Answer 104

• epigastric pain suggests foregut pathology

• central abdominal / umbilical pain suggests midgut pathology

• lower abdominal / suprapubic pain suggests hindgut pathology

Question 105

The liver

Answer 105

The liver is a large organ that lies in the right upper quadrant and epigastrium of the abdomen

The liver is protected by the ribs and moves inferiorly with inspiration – the lowermost part of the liver may be palpable below the right costal margin in inspiration.

Question 106

Function of liver

Answer 106

All the products of digestion, except lipids, are transported to the liver from the gut via the hepatic portal vein

The liver also produces bile, which is transported to the gallbladder for storage
Bile emulsifies lipids in the chyme entering the duodenum from the stomach

Question 107

The liver has two surfaces:

Answer 107

• The diaphragmatic surface lies anterosuperior and is related to the inferior surface of the diaphragm

• The visceral surface lies posteroinferior and is related to other organs

Question 108

The liver is mostly, but not entirely, covered by visceral peritoneum
The regions not covered by peritoneum are the:

Answer 108

• bare area of the liver – a region on the posterior surface that lies in contact with the diaphragm

• the region where the gallbladder lies in contact with the liver

• region of the porta hepatis – where hepatic blood vessels and ducts of the biliary system enter and exit the liver (the equivalent of the hilum of the lung)

Question 109

The liver is composed of two anatomical lobes

Answer 109

a large right lobe and a small left lobe

They are separated by the falciform ligament, which connects the anterior surface of the liver to the internal aspect of the anterior abdominal wall

Question 110

Two accessory lobes

Answer 110

the caudate and quadrate lobes, are located on the posteroinferior surface

These lobes do not represent the internal, functional organisation of the liver

Question 111

Internally the liver is organised into eight functional segments

Answer 111

Each segment is served by its own branch of the hepatic artery and portal vein, and by its own hepatic duct

Question 112

The liver is supplied by the right and left hepatic arteries
These branches ultimately derive from the coeliac trunk

Answer 112

• The coeliac trunk gives rise to the left gastric, splenic, and common hepatic arteries

• The common hepatic artery gives rise to the gastroduodenal artery; after this point, the common hepatic artery is called the hepatic artery proper (HAP)

• The hepatic artery proper bifurcates into right and left hepatic arteries, which enter the liver at the porta hepatis

Question 113

Venous blood exits the liver via two or three large hepatic veins that lie within the liver

Answer 113

they are not visible external to the liver

They unite with the inferior vena cava as it passes posterior to the liver

Question 114

It is a common mistake to confuse the hepatic veins with the hepatic portal vein. To be clear:

Answer 114

• Nutrient-rich venous blood that leaves the gut is transported to the liver via the hepatic portal vein, which receives blood from the superior and inferior mesenteric veins and the splenic vein

• Venous blood leaves the liver via the hepatic veins and enters the inferior vena cava

Question 115

The liver is served by the hepatic plexus, which is formed of parasympathetic fibres from the vagus nerves and sympathetic fibres

Answer 115

These fibres follow the paths of the hepatic vessels and ducts of the biliary tree

Because the liver is a foregut derivative, pain arising from it is referred to the epigastric region

Question 116

The liver is connected to the:

Answer 116

• diaphragm by the coronary and triangular ligaments

• anterior abdominal wall by the falciform ligament

• stomach and duodenum by the lesser omentum

Question 117

The hepatic artery, hepatic portal vein and the bile duct run together

Answer 117

as the portal triad in the free edge of the lesser omentum

Question 118

The portal triad and the free edge of the lesser omentum form the anterior boundary of the epiploic foramen;

Answer 118

the entrance into the lesser sac (which lies posterior to the stomach)

Question 119

There are two recesses related to the liver:

Answer 119

• The hepatorenal recess lies between the right kidney and the posterior (visceral) surface of the right side of the liver
Fluid flows into this space in the supine position

• The left and right subphrenic recesses lie either side of the falciform ligament, between the anterosuperior surface of the liver and the diaphragm.

Question 120

The liver develops from the embryological foregut

Answer 120

It grows from a tissue bud that develops in the ventral mesentery – a peritoneal fold in the upper abdomen that connects the stomach to the anterior abdominal wall

Question 121

As the liver grows and migrates to the right side of the abdomen, its peritoneal attachments are pulled with it

Answer 121

The remains of the ventral mesentery form the lesser omentum and the falciform ligament

The peritoneal attachments of the liver anchor it to surrounding structures, including the diaphragm superior to it.

Question 122

The free edge of the falciform ligament contains the round ligament of the liver (the ligamentum teres).

Answer 122

It is the remnant of the umbilical vein, which, in the foetus, carries oxygenated blood from the placenta to the foetus

Question 123

Another embryological remnant, the ligamentum venosum, lies on the posterior surface of the liver, in the groove between the caudate lobe and the left lobe of the liver

Answer 123

It is the remains of the ductus venosus, which in foetal life diverts blood from the umbilical vein to the IVC, thus shunting oxygen-rich blood to the heart and bypassing the liver

Question 124

The Gallbladder

Answer 124

The gallbladder stores and concentrates bile. It lies on the posteroinferior (visceral) surface of the liver and lies close to the duodenum

The gallbladder has three parts, the fundus, the body, and the neck

Question 125

The body

Answer 125

forms the main part of the gallbladder which sits in the gallbladder fossa on the visceral surface of the liver

It tapers towards the neck, which communicates with the cystic duct

The fundus is the rounded end of the gallbladder, which typically extends to the inferior border of the liver

Question 126

The surface marking of the fundus of the gallbladder

Answer 126

is at the tip of the 9th costal cartilage, at the point where the right midclavicular line intersects the right costal margin

Question 127

Bile is continuously produced by hepatocytes in the liver and is first excreted into small channels called bile canaliculi

Answer 127

The canaliculi drain into bile ducts of increasing calibre, which ultimately converge to form right and left hepatic ducts that exit the liver at the porta hepatis

Question 128

• The left and right hepatic ducts converge to form the common hepatic duct

• The common hepatic duct receives the cystic duct from the gallbladder. Distal to this point, the duct is called the bile duct (or common bile duct)

Answer 128

• The bile duct runs in the free edge of the lesser omentum

• It lies posterior to the superior part of the duodenum and posterior to the head of the pancreas

• The bile duct enters the duodenum

Question 129

If bile leaving the liver is not needed for digestion, it enters the gallbladder via the cystic duct

Answer 129

When needed, bile flows from the gallbladder, via the cystic duct, to the bile duct and duodenum.

The spiral fold (spiral valve) lies at the junction between the gallbladder neck and the cystic duct

Question 130

• Blood supply is via the cystic artery, which typically arises from the right hepatic artery (variation exists)

Answer 130

• The gallbladder is drained by cystic veins that pass directly into the liver or join the hepatic portal vein

Question 131

• The gallbladder is innervated by parasympathetic and sympathetic fibres

Answer 131

• Visceral afferents from the gallbladder return to the CNS with the sympathetic fibres

Visceral pain from the gallbladder enters spinal cord levels T5 – T9 and is therefore referred to (i.e. felt in) the epigastrium.

Question 132

• Gallbladder pain may also be referred to the right shoulder if gallbladder pathology (e.g. inflammation) irritates the diaphragm

Answer 132

The diaphragm is innervated by the phrenic nerve (C3-5)

Spinal cord segments C3-5 also receive somatic sensory information from the skin over the shoulder. Therefore gallbladder pathology involving the diaphragm may be felt in the right shoulder

• If gallbladder pathology irritates the parietal peritoneum, which is innervated by somatic nerves, pain is well localised to the right hypochondrium.

Question 133

The left and right nasal cavities form the first part of the respiratory tract

Answer 133

Mucosa in the upper part of the nasal cavity contains olfactory receptors

The axons of these receptors form the olfactory nerves (CN I)

Question 134

The left and right nasal cavities are separated from:

Answer 134

● each other by a thin midline septum, formed of cartilage and bone. When the head is bisected, the septum is seen on one half only

● the oral cavity inferiorly by the hard palate

● the brain superiorly by bone

Question 135

The nasal cavity communicates with the nasopharynx posteriorly

Answer 135

The nasal cavity also communicates with the paranasal sinuses, which are cavities within the skull bones

Question 136

The midline nasal septum is formed of cartilage anteriorly and two thin plates of bone posteriorly

Answer 136

The perpendicular plate of the ethmoid bone forms the superior part of the posterior septum, and the vomer forms the inferior part of the posterior septum.

Question 137

The lateral wall of the nasal cavity bears three projections of bone, the superior, middle, and inferior conchae (Latin = shell), or turbinates

Answer 137

● The spaces inferior to them are the meatuses: the superior meatus lies inferior to the superior concha; the middle meatus lies inferior to the middle concha and the inferior meatus lies inferior to the inferior concha

● As inspired air travels through the meatuses it is warmed, humidified, and filtered

Question 138

The nasal cavity is separated from the cranium and the brain by the cribriform plate

Answer 138

The cribriform plate is a delicate section of bone that is perforated with tiny holes (like a sieve)

The axons of olfactory neurons pass through these perforations to form the olfactory nerves, which travel to the brain

Olfactory receptors are located in the spheno-ethmoidal recess in the upper nasal cavity, between the superior concha and the cribriform plate

Question 139

The paranasal sinuses are cavities within the skull bones and are named according to the bones within which they are located:

Answer 139

● frontal sinuses lie within the anterior part of the frontal bone

● ethmoid air cells lie within the ethmoid bone (superior to the nasal cavity and medial to the orbits)

● sphenoid sinuses lie within the sphenoid bone

● maxillary sinuses lie within the maxillae of the facial skeleton.

Question 140

The frontal sinus and sphenoid sinus are usually clearly seen in the bisected head

Answer 140

The maxillary sinuses lie lateral to the lateral walls of the nasal cavity

Question 141

The paranasal sinuses communicate with the nasal cavity via small ducts / channels as follows:

Answer 141

● the frontal sinus drains into the middle meatus

● the sphenoid sinus drains into the spheno-ethmoidal recess

● the ethmoid air cells drain into the superior and middle meatuses

● the maxillary sinus drains into the middle meatus.

The opening of the maxillary sinus into the middle meatus lies superomedially, therefore it cannot drain feely when the head is upright.

Question 142

The nasal cavity also receives the nasolacrimal duct which drains the fluid (‘tears’) that lubricate the anterior surface of the eye

Answer 142

The duct opens into the inferior meatus.

When we cry, we get a runny nose because excess fluid runs down the nasolacrimal duct.

Question 143

The nasal cavity also communicates with the middle ear

Answer 143

The middle ear is a small cavity within the temporal bone that is modified for hearing (it contains three tiny bones that transmit sound waves to the inner ear)

Question 144

The auditory tube (Eustachian tube)

Answer 144

connects the middle ear to the nasopharynx.

The opening of the auditory tube can be seen on the lateral wall of the nasopharynx, surrounded by a slight bulge, which is formed of tonsillar tissue.

Question 145

The auditory tube allows air to pass into the middle ear so that the pressure on either side of the tympanic membrane (eardrum), which lies between the middle and external ear, is equal

Answer 145

This is important for optimal conduction of soundwaves

Question 146

The nasal cavity is supplied by several arteries

Answer 146

including branches of the maxillary artery, which is a terminal branch of the external carotid artery

An anastomotic network formed supplies the nasal septum and is often the site of bleeding in a nosebleed (epistaxis)

The sensory innervation of the nose is via branches of the trigeminal nerve (CN V).

Question 147

Function of the Palate

Answer 147

The palate separates the nasal cavities from the oral cavity.

Question 148

What is the palate composed of?

Answer 148

It is composed anteriorly of bone – the hard palate – and posteriorly of muscle – the soft palate.
The palate forms the roof of the oral cavity.

Question 149

The Hard Palate

Answer 149

The hard palate is composed of two bones: the palatine bone of the maxilla and the horizontal plate of the palatine bone.

Question 150

The hard palate is functionally important because:

Answer 150

● it prevents food or fluid entering the nasal cavity
● we push our tongue up against the hard palate during the first phase of
swallowing, which forces food and fluid backwards into the oropharynx
● we push our tongue up against the hard palate to articulate certain sounds

In some people the palate does not form properly during embryological development (a cleft palate), causing difficulty with eating, swallowing and speech if not repaired.

Question 151

The Soft Palate

Answer 151

The soft palate lies posterior to the hard palate

Question 152

uvula

Answer 152

A midline conical projection - the uvula - ‘hangs’ from the posterior border of the soft palate and can be seen at the back of the mouth

Question 153

The soft palate is composed of several muscles,

Answer 153

the muscles of the soft palate contract during swallowing which elevates the soft palate

The nasopharynx is closed off from the oral cavity, preventing reflux of food and fluid into the nasal cavity

The muscles of the soft palate are innervated by the vagus nerve

Question 154

The oral cavity is bounded:

Answer 154

● superiorly by the hard and soft palate (the roof of the mouth)

● inferiorly by soft tissues and muscles (the floor of the mouth)

● laterally by the cheeks (which contain the buccinator muscle)

Question 155

The oral cavity is continuous posteriorly with the oropharynx

Answer 155

It contains the tongue, teeth and gums and the openings of the salivary ducts

Question 156

The Teeth and Gums

Answer 156

● Adults have 32 teeth – 16 embedded in the maxilla (upper jaw) and 16 embedded in the mandible

Question 157

In the upper and lower jaws

Answer 157

there are four incisors, two canines, four premolars
and six molars

Question 158

The teeth are composed of:

Answer 158

● an inner pulp which contains blood vessels and nerves

● dentin which surrounds the pulp

● an outer, hard coating of enamel

Question 159

Enamel and dentin can be eroded by bacteria or foodstuffs (e.g. sugar and acids).

Answer 159

This can lead to decay, inflammation, and infection of the pulp, which is painful

Infection may spread to the bone, leading to abscess formation

Question 160

The Tongue

Answer 160

The tongue is essential for normal chewing, swallowing and speech

It bears papillae on its superior surface, some of which detect taste (‘taste buds’)

The anterior part of the tongue lies in the oral cavity, and the posterior part (the root) extends into the oropharynx

Question 161

Vallecula

Answer 161

The space between the posterior tongue and the anterior aspect of the epiglottis

Question 162

The tongue is composed of 2 types of muscles

Answer 162

Intrinsic

Extrinsic

Question 163

Intrinsic muscles

Answer 163

lie entirely within the tongue. They are paired bilaterally and fuse in the midline. They change the shape of the tongue.

Question 164

Extrinsic muscles

Answer 164

are attached to the tongue but originate from outside it (from the mandible and hyoid bone). They move the tongue

Question 165

The muscles are innervated by the hypoglossal nerve (CN XII)

Answer 165

The sensory innervation of the tongue is via three cranial nerves:

● Taste in the anterior two thirds is served by the facial nerve (CN VII)

● General sensation (touch, pain, temperature) in the anterior two thirds is served by the trigeminal nerve (CN V)

● Taste and general sensation in the posterior third are served by the glossopharyngeal nerve (CN IX)

Question 166

Vessels and Nerves of the Oral Cavity

Answer 166

● The oral cavity is supplied by the lingual, maxillary, and facial arteries, which are branches of the external carotid artery

● Innervation of the oral cavity is complex
The muscles of the soft palate are innervated by the vagus nerve
The tongue is innervated by four cranial nerves (CNs V, VII, IX and XII) as described above

Question 167

Tonsillar tissue is found in several locations in the nasal and oral cavities

Answer 167

The pharyngea

The tubal

The palatine

The lingual

Question 168

The pharyngeal tonsil

Answer 168

lies in the roof and posterior wall of the nasopharynx (sometimes called the ‘adenoid’)

Question 169

The tubal tonsil

Answer 169

surrounds the opening of the auditory tube on the lateral wall of the nasopharynx

Question 170

The palatine tonsil

Answer 170

lies on the lateral wall of the oropharynx.

Usually referred to as ‘the tonsils’, they are visible on either side of the oropharynx when the mouth is open.

Question 171

The lingual tonsil

Answer 171

Is a collection of lymphoid tissue in the posterior tongue

Question 172

The coeliac trunk leaves the anterior aspect of the aorta at the level of T12. It gives rise to three major branches:

Answer 172

• The left gastric artery – supplies the distal oesophagus and lesser curvature of the stomach

• The common hepatic artery – branches supply the liver, stomach, and duodenum

• The splenic artery – branches supply the stomach, pancreas, and spleen

Question 173

The duodenum is the first and shortest part of the small intestine
It is continuous proximally with the pylorus of the stomach and distally with the jejunum

Answer 173

The pyloric sphincter regulates gastric emptying into the duodenum

Question 174

• Most of the duodenum is retroperitoneal

• The duodenum forms a C-shape that cups the head of the pancreas

• The duodenum is described in four parts. These are the superior (first), descending (second), the inferior (third) and the ascending (fourth) parts

Answer 174

• The bile duct, gastroduodenal artery and the hepatic portal vein lie posterior to the first part of the duodenum

• The superior mesenteric artery lies anterior to the third part

• The fourth part meets the jejunum at the duodenojejunal flexure

Question 175

• Approximately halfway along the internal wall of the duodenum is a small elevation called the major duodenal papilla (papilla = nipple-like)

Answer 175

This marks the point at which bile and digestive pancreatic secretions (‘pancreatic juice’) enter the duodenum

Question 176

The first half of the duodenum is derived from the foregut and is supplied by branches of the coeliac trunk (the artery of the foregut)
The second half is derived from midgut and is supplied by branches of the superior mesenteric artery (the artery of the midgut)
Arterial branches that supply the duodenum are derived from the:

Answer 176

• gastroduodenal artery (from the common hepatic artery and hence the coeliac trunk)

• inferior pancreaticoduodenal arteries (from the superior mesenteric artery)

Veins follow the arteries and are tributaries of the hepatic portal vein.

Question 177

The pancreas lies horizontally on the posterior abdominal wall at the level of L1 and is retroperitoneal

It does not have a capsule so in the cadaver its surface appears ‘bumpy’ rather than smooth

Answer 177

• It forms from dorsal and ventral pancreatic buds which fuse during development

• It is composed of four parts: the head, the neck, the body, and the tail

• The uncinate process is a hook-like projection of the head of the pancreas

Question 178

• The head is cupped by the C-shaped duodenum and the tail extends to the hilum of the spleen

• The pancreas forms part of the posterior wall of the lesser sac

Answer 178

• The splenic artery runs towards the spleen embedded in the upper border of the pancreas. The splenic vein lies posterior to the pancreas

• The main pancreatic duct and the accessory pancreatic duct run within the substance of the pancreas

Question 179

The pancreas has an endocrine and an exocrine function

Answer 179

It synthesizes and secretes insulin and glucagon

Insulin is released in response to high levels of glucose in the blood. The pancreas also produces pancreatic juice that contains digestive enzymes.

Pancreatic juice is transported through main pancreatic duct and the accessory pancreatic duct to the duodenum. The main and accessory pancreatic ducts usually communicate with each other.

Question 180

The duodenum receives:

Answer 180

• bile from the liver and gallbladder via the bile duct

• pancreatic juice from the pancreas via the main and accessory pancreatic
ducts.

Question 181

The bile duct and main pancreatic duct merge at the hepatopancreatic ampulla (ampulla = dilation)

Answer 181

The hepatopancreatic ampulla opens into the second part of the duodenum at the major duodenal papilla, which is located on the internal wall of the duodenum, about halfway along its length

Question 182

The hepatopancreatic ampulla is surrounded by smooth muscle - the sphincter of Oddi

Answer 182

Contraction of the sphincter prevents reflux of duodenal contents into the bile and main pancreatic ducts

The accessory pancreatic duct empties pancreatic juice into the duodenum at the minor duodenal papilla, which lies just proximal to the major duodenal papilla

Question 183

The pancreas is supplied by blood vessels derived from the coeliac trunk and blood vessels derived from the superior mesenteric artery:

Answer 183

• The splenic artery, a major branch from the coeliac trunk, runs along the upper border of the pancreas and gives rise to pancreatic arteries

• The gastroduodenal artery (from the common hepatic artery and hence the coeliac trunk) gives rise to the superior pancreaticoduodenal arteries that supply the pancreas

• The superior mesenteric artery gives rise to the inferior pancreaticoduodenal arteries that supply the pancreas

Question 184

Veins follow the arteries

Answer 184

The splenic vein drains the pancreas and unites with the superior mesenteric vein to form the hepatic portal vein posterior to the neck of the pancreas

Question 185

The spleen is a haematopoietic and lymphoid organ that lies in the left upper quadrant, protected by ribs 9 - 11

It is covered with visceral peritoneum

Answer 185

It has several functions that include the breakdown of old red blood cells, the storage of red blood cells and platelets, and various immune responses, including production of IgG

Question 186

The spleen has two surfaces and four borders:

Answer 186

• the diaphragmatic surface lies adjacent to the diaphragm

• the visceral surface lies in contact with the stomach, left kidney and colon. The splenic vessels enter and exit the spleen at the hilum on the visceral surface

• the anterior and superior borders are typically notched

• the posterior and inferior borders are smooth

A normal sized spleen is not palpable below the costal margin
If it is palpable, it is enlarged by at least three times its normal size

Question 187

The spleen is supplied by the splenic artery, a branch of the coeliac trunk

The splenic artery runs along the superior border of the pancreas, embedded within it

The artery divides into approximately five branches at the hilum

Answer 187

Venous drainage is via the splenic vein, which runs posterior to the pancreas

It unites with the superior mesenteric vein to form the hepatic portal vein