Anatomy Flashcards
(224 cards)
1
Q
Name the components of the GI tract from head to perineum
A
- head; oral cavity, pharynx
- neck; pharynx, oesophagus
- chest; oesophagus
- abdomen; stomach small intestine, large intestine, most accessory organs of the GI tract
- pelvis; rectum, anal canal
- perineum; anus
2
Q
What are the four main functions of the upper GI tract?
A
- mastication
- taste
- deglutition (swallowing)
- salivation
3
Q
What structures are involved in mastication?
A
- temporomandibular joint
- muscles of TMJ, face and tongue
- dentition (teeth)
4
Q
What structures are involved in taste?
A
- tongue
- salivation
- mastication
5
Q
What structures are involved in deglutition?
A
- tongue
- palate
- pharynx
- oesophagus
6
Q
What structures are involved in salivation?
A
- parotid gland
- submandibular gland
- sublingual gland
- minor glands
7
Q
Describe mastication
A
- the process of chewing
- conducted by the movement of the jaw and tongue, to breakdown food
- mastication facilitates taste and digestion by mixing food with saliva
8
Q
Name the four quadrants of teeth
A
- upper right
- upper left
- lower left
- lower right
9
Q
What is the upper and lower dental arches referred to?
A
- upper = maxillary
- lower = mandibular
10
Q
How many teeth do adults have?
A
32
11
Q
Name the types of teeth and what number they refer to
A
- molars; 6,7,8
- premolars; 4 and 5
- canine; 3
- incisor; 1 and 2
- wisdom tooth; 8
12
Q
Where does the opening and closing of the jaw occur?
A
TMJ, temporomandibular joints
13
Q
The 4 muscles of mastication are supplied by which nerve?
A
- CN V3
- mandibular division of trigeminal nerve
14
Q
What is the masseter muscle?
A
Angle of mandible to zygomatic arch
15
Q
What is the temporalis m?
A
Coronoid process of mandible to temporal fossa
16
Q
What is the later pterygoid?
A
- muscle
- condyle of mandible to pterygoid plates of sphenoid bone
17
Q
What is the medial pterygoid?
A
- muscle
- angle of mandible (medial side) to pterygoid plates of sphenoid bone
18
Q
The mandibular division of trigeminal nerve (CNV3) provides what types of fibres?
A
- sensory
- motor
19
Q
Describe the course of the mandibular division of trigeminal nerve (CNV3)
A
- from pons
- through foramen ovale
- to muscles of mastication and sensory area
20
Q
What are the four types of papillae?
A
- foliate papillae
- vallate papillae
- fungiform papillae (singular papilla)
All with taste buds - filiform papillae (touch, temperature etc)
21
Q
Describe the course of the facial nerve
A
- from pontomedullary junction
- travel through temporal bone via internal acoustic meatus then stylomastoid foramen
22
Q
The facial nerve supplies what with which fibres?
A
- supply taste to the anterior 2/3 of the tongue
- muscles of facial expression
- glands in floor of mouth
- special sensory, sensory, motor and parasympathetic
23
Q
Describe the sensation supply of the superior half of the oral cavity
A
- gingiva of oral cavity and palate
- general sensation CN V2
24
Q
Describe the sensation supply of the inferior half of the oral cavity
A
- gingiva of oral cavity and floor of mouth
- general sensation CNV3
25
Describe the gag reflex
- a protective reflex that prevents foreign bodies from entering the pharynx or larynx
- the sensory part of this reflex is carried by nerve fibres within CN IX
- the motor part is carried by nerve fibres within CN IX and CN X
- part of the reflex response to touching the posterior wall of the oropharynx is to constrict the pharynx, as the patient attempts to dose it off as an entry point into the body
26
What is the purpose of spraying a local anaesthetic at the back of the throat?
Will block sensory action potentials in CNV2, CNV3, CN VII and CNIX
- numbs the area ready for the endoscope
27
Describe the course of CNV2
- maxillary division of trigeminal nerve (CNV2), sensory fibres
- course; from pons, through foramen rotundum, to sensory area (mid-face)
28
Describe the course of the glossopharyngeal nerve (CN IX)
- from medulla
- through jugular foramen
- to posterior wall of oropharynx (sensory), parotid gland (secretomotor) and post 1/3rd tongue (sensation and taste)
29
Describe the surface anatomy of the parotid gland
- parotid duct crosses face, secretes into mouth by upper 2nd molar
30
Describe the surface anatomy of the submandibular gland
- submandibular duct enters floor of mouth and secretes via lingual caruncle
31
Describe the surface anatomy of the sublingual gland
- lays in floor of mouth, secretes via several ducts superiorly
32
What are the three pairs of salivary glands and which nerve supplies them?
- parotid; CNIX
- submandibular; CNVII
- sublingual; CNVII
33
Describe the extrinsic muscles of the tongue
Function to change the position of the tongue during mastication, swallowing and speech
34
Describe the intrinsic muscles of the tongue
- 4 pairs of skeletal intrinsic muscles
- located dorsally / posteriorly
- modify the shape of the tongue during function
35
All tongue muscles are innervated by which nerve?
The hypoglossal nerve (CNX11)
EXCEPT PALATOGLOSSUS
36
Describe the course of the hypoglossal nerve (CNXII)
- from medulla
- through hypoglossal canal
- to extrinsic and intrinsic muscles of the tongue (except palatoglossus)
37
Describe the posterior view of the pharynx
- 2 circular constrictor muscles
- voluntary muscle
- external circular layer overlap each other and contract sequentially
- innervated by CN X (vagus)
- all insert onto the midline raphe
- both layers elevate pharynx and larynx, attach to larynx, contract to shorten pharynx, raise the larynx to close over the laryngeal inlet
38
Describe the anatomy of swallowing
- close the lips to prevent drooling (orbicularis oris and cranial nerve VII)
- the tongue (cranial nerve XII) pushes the bolus posteriorly towards the oropharynx
- sequentially contract the pharyngeal constrictor muscles (cranial nerve X) to push the bolus inferiorly towards the oesophagus
- at the same time he inner longitudinal layer of pharyngeal muscles (cranial nerves IX and X) contracts to raise the larynx, shortening the pharynx and closing off the laryngeal inlet to help prevent aspiration
5. the bolus reaches the oesophagus
39
Describe the enteric nervous system
- extensive network of nerves, found only in walls of GI tract
- acts independently of other parts of nervous system, but can also be influences by autonomic motor nerves
- parasympathetics (speed up peristalsis)
- sympathetics (slow down peristalsis)
40
Where does the oesophagus begin?
Begins at the inferior edge of circopharyngeus muscle (vertebral level 6)
41
Describe the oesophagus
- inferior continuation of laryngopharynx
- is a muscular tube, walls sit together when there is no food present
- has an anatomical upper sphincter and a physiological lower oesophageal sphincter
- aid in controlling movement
42
Describe the oesophageal plexus
- runs on surface to supply smooth muscle within its walls (distally)
- contains parasympathetic nerve fibres (vagal trunks) and sympathetic nerve fibres
- these fibres influence the enteric nervous system to speed up (P) or slow down (S) peristalsis
43
Where does the oesophagus terminate?
Terminates by entering the cardia of the stomach
44
Describe the position of the oesophagus in the root of the neck
- posterior to trachea
| - anterior to vertebral bodies
45
Describe the position of the oesophagus in the chest
- posterior to the heart
| - in contact with the left atrium
46
Describe the position of the oesophagus in the abdomen
- through diaphragm at T10 vertebral level
| - immediately connects with stomach
47
Describe the cervical constriction of oesophageal positioning
- circopharyngeus muscle
48
Describe the thoracic constrictions of oesophageal positioning
- arch of aorta
| - left main bronchus
49
Describe the diaphragmatic constriction of oesophageal positioning
- result of passing through diaphragm
| - lower oesophageal sphincter
50
Describe the lower oesophageal sphincter
- physiological rather than anatomical sphincter
- helps reduce the occurrence of reflex
- presence of a hiatus hernia will reduce its effectiveness can lead to reflux
- lies immediately superior to gastro-oesophageal junction
- abrupt change in type of mucosa lining the wall - zline
51
Name factors that produce the sphincter effect
- contraction of diaphragm
- intrabdominal pressure slightly higher than intragastric pressure
- oblique angle at which oesophagus enters the cardia of stomach
52
Describe the anatomical position of the stomach
- lies mainly in the left hypochondrium, epigastric and umbilical regions when the patient is supine
53
What is the fundus?
The superior part of the stomach
54
Describe the arterial supply to the abdominal organs
- three midline branches of the abdominal aorta
- coeliac trunk (foregut organs)
- superior mesenteric artery (midgut organs)
- inferior mesenteric artery (hind gut organs)
55
Describe the formation of the vitelline duct
- initially the midgut is completely open into the yolk sac
- as folding continues it narrows for a connecting, vitelline duct
- it becomes incorporated into the umbilical cord
56
Describe the formation of the oesophagus
- respiratory diverticulum appears end of week 3
- weeks 4-7 oesophagus lengthens rapidly due to descent of heart and lungs
- failure of oesophagus to grow in proportion with neck and thorax can lead to a short oesophagus
- resulting in stomach being placed cranially in the thorax forming a congenital hiatal hernia
57
Describe the formation of the stomach
- stomach starts as a fusiform dilation
- dorsal wall undergoes rapid growth to form the greater curvature
- ventral wall growth is slower resulting in the lesser curvature
58
Describe the rotation of the stomach
- clockwise 90 degrees around the longitudinal axis (LARP, left anterior, right posterior)
- anteroposterior axis rotation brings pyloris upwards and fundus downwards
59
Describe the primitive dorsal and ventral mesenteries
- mesenteries are a continuous layer of serous membrane
| - they attach the gut tube to the anterior (ventral) and posterior (dorsal) walls of the abdomen
60
Describe the formation of the omental bursa
- omental bursa (AKA lesser peritoneal sac) is the (peritoneal) space posterior to the stomach
- rapid growth of dorsal mesentery and stomach rotation around the longitudinal axis
- the rest of the space in the peritoneal cavity is known as the greater sac
- epiploic foramen (of winslow) connects the two (greater and lesser sacs)
61
Describe the foramen of the greater omentum
- dorsal mesentery continues to develop as a double layered sac over the small intestine and transverse colon
- these layers fuse to extend from the greater curvature of the stomach
- forming the greater omentum (apron like structure)
62
Describe the formation of the duodenum
- both foregut and midgut structure
- as stomach rotates the duodenum move from the midline to the right side of the abdominal cavity
- dorsal mesentery fuses with peritoneum covering the posterior abdominal wall
- duodenum (parts 2 and 3) and pancreas become retroperitoneal
63
Describe the development of the midgut
- in week 5, mid gut rapidly expands forming the primary intestinal loop
- cranial (cephalic) limb, distal duodenum, jejunum and upper ileum
- caudal limb - lower ileum, cecum, ascending colon and proximal 2/3rds of transverse colon
64
Describe physiological herniation of the midgut
- in week 6, rapid growth and expansion of the liver causes physiological herniation of midgut
- the cranial (cephalic) limb continues to lengthen
- intestinal loops move through umbilical cord to lie outside the developing embryo
65
Describe rotation of the midgut
- as lengthening continues, the midgut rotates 90 degrees clockwise (patients perspective) and herniates through umbilical cord
- small intestine and large intestine growth continues to form coils (large intestine does coil)
- during week 10, intestines retract back into abdomen with a further 180 degree clockwise turn (270 degrees total)
- jejunum first then cecal bud
- cecal bud then descends from right lobe of liver to right iliac fossa
66
Describe fixation of intestines
- the dorsal mesentery of the gut is still present and connects to the posterior abdominal wall
- connected around the axis of the superior mesenteric artery
- the ascending and descending colon mesentery fuse with peritoneum to place them in retroperitoneal space
67
What is omphalocele?
- failure of intestinal loop to return into abdomen
- presents as shiny sac at the base of umbilical cord
- 2.5/10,000 births
- high mortality rate
- often associated with cardiac and neural tube defects
68
What is gastrochisis?
- protrusion of abdominal content through wall lateral to umbilical cord
- due to abnormal closure around the connecting stalk
- 1 in 10,000 births
69
Describe the development of the hindgut
- terminal end of hindgut is an endodermal lined pouch called the cloaca
- in contact with surface ectoderm of proctodeum to form the cloacal membrane
- urorectal septum partitions the cloaca into; upper rectum . anal canal and urogenital sinus
- urorectal septum fuses with the cloacal membrane at the future site of the perineal body
70
Describe the formation of the liver and biliary system
- a ventral overgrowth of foregut end weeks 3 into ventral mesentery
- outgrowth termed hepatic diverticulum (liver bud) that penetrate septum transversum
- cranial portion = liver
- caudal portion = bile duct
71
Outgrowth from the bile duct gives rise to what?
The gallbladder and cystic duct
72
Describe the formation of the liver
- hepatic cords form, which intermingle with the umbilical and vitelline veins to give hepatic sinusoids
- vitelline veins carry poorly oxygenated but nutrient rich blood to the developing embryo
- endoderm; liver cells (parenchyma) and lining of biliary tree
- septum transversum; hematopoietic cells, Kupffer cells and connective tissue
73
Describe the formation of the spleen
- mesoderm derivative (not gut tube)
- develops in 5th week
- initially haematopoetic
- develops into lymphatic organ during weeks 15-18
- lobular appearance but lobes normally regress before birth, notches in adults
74
Describe the small intestine
- around 7m long and from proximal to distal is made up of;
- duodenum (short)
- jejunum (3m)
- ileum (4m)
75
Describe the large intestine
- from proximal to distal is made up from;
- colon; caecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon)
- rectum
- anal canal
- anus
76
Nam the abdominal organs
- liver
- oesophagus
- stomach
- gall bladder
- pancreas
- large intestine
- small intestine
- rectum
- anal canal
- anus
- spleen
- kidneys
- adrenal glands
77
Name the abdominal organs of the foregut
- oesophagus to mid-duodenum
- liver and gall bladder
- spleen
- 1/2 of pancreas
78
Name the abdominal organs of the midgut
- mid-duodenum to proximal 2/3rds of transverse colon
| - 1/2 of pancreas
79
Name the abdominal organs of the hindgut
- distal 1/3 of transverse colon to proximal 1/2 of anal canal
80
What are the nine regions of abdominal organs?
- right hypochondrium
- epigastric
- left hypochondrium
- right lumbar
- umbilical
- left lumbar
- right inguinal
- pubic
- left inguinal
81
What is the peritoneum?
- a thin, transparent, semi-permeable serous membrane
| - it lines the walls of the abdominopelvic cavities and organs
82
What lies between the visceral and parietal layers of peritoneum?
The peritoneal cavity, contains a small amount of lubricating fluid
83
What is peritonitis?
- blood, pus, faeces in the peritoneal cavity
| - causes severe and painful inflammation of the peritoneum
84
How are organs classes depending on their relationship with the peritoneum?
- intraperitoneal
- retroperitoneal
- with a mesentery
85
Describe the intraperitoneal organs
- almost completely covered in visceral peritoneum
| - minimally mobile
86
Describe the organs with a mesentery (intraperitoneal)
- covered in visceral peritoneum
- visceral peritoneum wraps behind the organ to form a double layer - mesentery
- mesentery suspends the organ from the posterior abdominal wall - very mobile
87
Describe the retroperitoneal organs
- only has visceral peritoneum on its anterior surface
| - located in the retroperitoneum
88
What are the three type s of peritoneal formation?
- mesentery; usually connects organ to posterior body wall
- omentum (greater and lesser); double layer of peritoneum that passes from stomach to adjacent organs
- peritoneal ligaments; double layer of peritoneum that connects organs to one another or body wall
89
Describe the mesentery peritoneal formation
- have a core of connective tissue with blood and lymph vessels, nerve, lymph nodes and fat
- the mesentery proper of small intestine
- transverse and sigmoid mesocolon
- mesoappendix
- mesentery provide high level mobility
90
Describe the greater omentum
- four-layered
- hangs like an apron
- attaches the greater curvature of stomach to transverse colon
91
Describe the lesser omentum
- double-layered
- runs between lesser curvature of stomach and duodenum to liver
- has a free edge
92
The omenta divide the peritoneal cavity into what?
- greater and lesser sacs
- the lesser sac is much smaller
- the two sacs communicate through the omental foramen (foramen of winslow)
- the portal triad lies in the free edge of the lesser omentum
93
What are ascites?
A collection of fluid in the peritoneal cavity
94
Ascites are most commonly caused by what?
- liver disease
- cirrhosis
- portal hypertension
95
How can ascitic fluid be drained?
Paracentesis, abdominocentesis
96
Describe abdominocentesis
- during paracentesis, the needle must be placed lateral to the rectus sheath
- this avoids the inferior epigastric artery; ascends in anterior abdominal wall (deep to rectus abdominis)
- inferior epigastric arises from the external iliac medial to the deep inguinal ring
- use ultrasound guidance if available
97
Describe the nerves of organs within the abdominal cavity
- includes visceral peritoneum
- visceral afferents (sensory nerves)
- the enteric nervous system
- the autonomic motor nerves; can influence the enteric nervous system
98
Describe the nerves of the abdominal wall of the abdominal cavity
- from skin through to parietal peritoneum
- somatic sensory nerves
- somatic motor nerves
- sympathetic nerve fibres
99
Describe the nerves of the adrenal gland
- sympathetic nerve fibres for the adrenal gland leave the spinal cord (T10 - L1)
- enter the abdominopelvic splanchic nerves
- do not synapse at prevertebral ganglia
- are carried with periarterial plexuses to the adrenal gland
- synapse directly onto cells
100
What links the liver, spleen, gallbladder, pancreas and small intestines?
Linked together by the formation of bilirubin, bile and the clinical condition of jaundice
101
What is bilirubin?
Normal by-product of the break down of red blood cells
102
Where does the breakdown of red blood cells mainly occurs where?
In the spleen
103
What is the function of bilirubin?
Used to form bile iin the liver
104
What is the biliary tree?
A set of tubes connecting the liver to the 2nd part of the duodenum
105
What is the role of the gallbladder?
Plays an important role in the storage and concentration of bile
106
Bile is important for what?
For the normal absorption of fats from the small intestine
107
Where is the portal triad found?
In the free edge of the lesser omentum
108
What does the portal triad consist of?
- hepatic artery
- hepatic portal vein
- common bile duct
109
What is the role of the portal triad?
Arterial blood supply to and venous drainage to the liver. Part of biliary tree linking liver to duodenum. Also contains nerve and lymphatics
110
What is the first of the three branches of the abdominal aorta?
The coeliac trunk
111
Describe the coeliac trunk
- is retroperitoneal
- arises around T12 vertebral level
- supplies the organs of the foregut
112
The coeliac trunk trifurcates into what?
- splenic artery
- hepatic artery
- left gastric artery
113
Which artery is described as having a tortuous course?
The splenic artery
114
Where is the spleen located?
- intraperitoneal organ within left hypochondrium
- related to diaphragm posteriorly
- related to stomach anteriorly
- related to the splenic flexure inferiorly
- related to the left kidney medially
115
Name the function of spleen
- functions within the haematological system
| - breaks down red blood cells to produce bilirubin
116
The spleen is protected by what?
- protected by ribs 9-11
- rib fracture could pierce the soft, delicate spleen
- substantial internal bleeding
117
Describe the blood supply to the stomach
- right and left gastric arteries which run along the lesser curvature and anastomose together
- right and left gastro-omental arteries, run along the greater curvature, anastomose together
118
The blood supply to the liver comes from where?
- hepatic artery
- branches into right and left hepatic arteries
- only accounts for 20-25% of the blood received by the liver, rest is from hepatic portal vein
119
Describe the anatomical relations of the liver
Related to;
- the diaphragm superiorly, anteriorly, posteriorly
- the anterior aspect of the stomach medially
- the gallbladder posterior and inferiorly
- the hepatic flexure inferiorly
- the right kidney, right adrenal gland, IVC and abdominal aorta posteriorly
120
The liver is protected by what?
By ribs 7-11
121
Where does the liver lie?
Mainly in the upper right quadrant
122
What is the function of the liver?
- major metabolic organ
| - converts bilirubin to bile
123
Name the four anatomical segments of the liver
- right lobe
- left lobe
- caudate lobe
- quadrate lobe
124
The liver has how many functional segments?
8
125
Venous drainage from the liver is via what?
- 3 main hepatic veins into the IVC
126
What can cause hepatomegaly?
- the IVC and hepatic veins lack valves
- a rise in central venous pressure is directly transmitted to the liver
- can enlarge as it engorges with blood
127
Where are interlobular portal triads found?
- liver lobule with central vein in middle and an at each corner
128
What is the role of the central vein?
Collects cleaned blood and drains into the hepatic veins
129
Name the two clinically important areas of the peritoneal cavity related to the liver
- hepatorenal recess (morrisons pouch)
| - sub-phrenic recess
130
Describe the hetroperitoneal recess
One of the lowest parts of the peritoneal cavity when the patient is supine
131
Describe the drainage from the hepatic portal vein
Drains blood from foregut, midgut and hindgut to the liver for first pass metabolism (cleaning)
132
Describe the drainage of the splenic vein
Drains blood from the foregut to the hepatic portal vein
133
Describe the drainage of the inferior mesenteric vein
Drains blood from the hindgut to the splenic vein
134
Describe the inferior vena cava
- retroperitoneal
| - drains the cleaned blood from the hepatic veins into the right atrium
135
What is the ligamentum teres?
Round ligament, remnant of the embryological umbilical vein
136
Describe the gallbladder
- lies on the posterior aspect of the liver (often firmly attached)
- lies anterior to the duodenum
- stores and concentrates bile in between meals
- has a body and neck, the neck narrows to become the cystic duct
- bile flows in and out of the gallbladder via the cystic duct
- blood supply is via the cystic artery, branch of the hepatic artery in 75% of people
137
Where is the potential site for gall stone impaction?
The neck narrows to become the cystic duct this narrowing is a potential site for gall stone impaction
138
Describe the structure of the biliary tree
- made up of a number of ducts which transport bile
| - right and left hepatic ducts unit to form the common hepatic ducts
139
The common hepatic duct unites with what to firm the bile duct (common bile duct)?
The cystic duct
140
Where does the bile duct drain into?
2nd part of the duodenum
141
The bile duct descends posteriorly to what?
The 1st (superior) part of the duodenum
142
What travels into a groove on the posterior aspect of the pancreas?
The bile duct
143
What forms the ampulla of vater / hepatopancreatic ampulla?
The joining of the bile duct with the main pancreatic duct
144
The ampulla of vater drain into the 2nd part of the duodenum through what?
Through the major duodenal papilla
145
What is an anatomical sphincter?
Discrete areas where muscle completely encircles the lumen of the tract
146
Name the smooth muscle sphincters in the bile duct area
- bile duct sphincter
- pancreatic duct sphincter
- sphincter of oddi
147
What is the aim of the smooth muscle sphincter in the bile duct area?
To prevent the reflux of digestive secretions and duodenal content,
148
Which sphincter plays a significant role in controlling the flow of bile into the duodenum?
The bile duct sphincter
149
What is endoscopic retrograde cholangiopancreatography? (ECRP)
Investigation used to study the biliary tree and pancreas and treat some pathologies associated with it
150
Describe how endoscopic retrograde cholangiopancreatography (ECRP) is performed
- endoscope inserted through oral cavity, oesophagus, stomach and into the duodenum
- cannula placed into major duodenal papilla and radio-opaque dye injected back into biliary tree
- radiographic images are taken of the dye-filled biliary tree
151
Give an example of a pathology the endoscopic retrograde cholangiopancreatography can treat
Bile duct stones
152
Name some extra hepatic obstructive causes of jaundice
- obstruction of the biliary tree
- gallstones
- carcinoma at head of pancreas
153
Name the four parts of the pancreas
- head (with uncinate process)
- neck
- body
- tail
154
What type of digestive organ is the pancreas?
An accessory digestive organ
155
Describe the position of the pancreas
- lying between duodenum on the right and the spleen on the left
- posterior to the stomach
- retroperitoneal organ
156
What is the ucinate?
A small projection from the inferior part of the head of the pancreas and lies posterior to the superior mesenteric artery
157
Where does the head of the pancreas lie?
Lies over the superior mesenteric vessels
158
Where does the body of the pancreas lie?
Over the aorta and L2 vertebra
159
Where does the tail of the pancreas lie?
To the left kidney
160
What supplies sympathetic innervation to the pancreas?
Abdominopelvic splanchic nerves
161
What supplies parasympathetic innervation to the pancreas?
Vagus nerves
162
Name a cause of pancreatitis
A blockage of the ampulla by a gallstone, bile is then diverted into the pancreas leading to irritation and inflammation
163
Where would pain from the pancreas arise and why?
- present in the epigastric and or umbilical region
- can also radiate through to the back
- this is because it is a foregut and a midgut organ
164
Name the three sections of the small intestines
- duodenum
- jejunum
- ileum
165
Are the small intestines foregut, midgut or hindgut organs?
- the 1st and 2nd parts of the duodenum are foregut organs
| - the rest of the small intestines are midgut organs
166
Name the four parts of the duodenum
- superior (part intraperitoneal)
- descending (retroperitoneal)
- horizontal (retroperitoneal)
- ascending (retroperitoneal)
167
Where does the duodenum begin?
At the pyloric sphincter
168
Describe the pyloric sphincter
- anatomical sphincter controlling the flow of chime from stomach to duodenum
- smooth muscle; autonomic nerves
169
Where does pain from a duodenal ulcer tend to present?
In epigastric region
170
What is the sympathetic influence on the pyloric sphincter?
Promotes contraction
171
What is the parasympathetic influence on the pyloric sphincter?
Innervation promotes relaxation
172
Where does the jejunum begin?
At the duodenaljejunal flexure
173
Where does the ileum end?
At the ileocaecal hunction
174
Where is the duodenal-jejunal flexure usually found?
Around the L2 vertebral level, a few cm to the left of the midline
175
Describe the mucosa of the jejunum
It is highly folded. The folds are called plicae circularis, mucosa of the distal ileum is much smoother
176
The jejunum and ileum receive arterial blood from where?
- superior mesenteric artery
| - via jejunal and ileal arteries
177
The jejunum and ileum receive venous drainage from where?
- jejunal and ileal veins
- to superior mesenteric vein
- to hepatic portal veins
- proteins and carbohydrates are absorbed from the small intestine into the portal venous system to be taken t the liver
- vessels travel within the mesentery
178
Describe the differences of arterial blood supply to ileum and jejunum
- jejunum tends to have greater vascularity with long vasa recta (the straight arteries) and few large loops of arterial cascades (where the arteries unite to form arches or loops)
- the ileum tends to have less vascularity with short vasa recta and many shorted looped arcades
179
Name the main groups of lymph nodes draining abdominal organs
- celiac (foregut organs)
- superior mesenteric (midgut organs)
- inferior mesenteric (hindgut organs)
- lumbar (kidneys, posterior abdo wall, pelvis and lower limbs
180
Superficial lymph vessels drain into what?
Deep lymph vessels
181
How many paracolic gutters are there?
2
182
Describe the paracolic gutters
- left and right
- between lateral edge of ascending and descending colon and abdominal wall
- part of greater sac of peritoneal cavity
- potential sites for pus collection
- similar to subphrenic or hepatorenal recesses
183
Which structure lies more superiorly, splenic flexure or hepatic flexure?
Splenic flexure
184
Describe the teniae coli
- 3 distinct longitudinal bands of thickened smooth muscle
| - running from caecum to distal end of sigmoid colon
185
Where do the caecum and appendix both sit?
In the right iliac fossa
186
Describe the position of the appendix
- variable
- most often retrocaecal
- variety accounts for the different ways in which patients can present with appendicitis
187
Where is the appendiceal orifice?
In posteromedial wall of caecum
- corresponds to mcburneys point on the anterior abdominal wall
- 1/3 of the way between right ASIS to umbilicus
- maximum tenderness in case of appendicitis (in theory)
188
Describe the sigmoid colon
- lies in the left iliac fossa
- has a long mesentery (sigmoid mesocolon)
- gives it a considerable degree of movement
- negative side; sigmoid colon at risk of twisting around itself, sigmoid volvulus
- clinically results in bowel obstruction
- bowel at risk of infarction if left untreated
189
Describe the abdominal aorta
- midline, retroperitoneal structure
| - lies anterior to vertebral bodies and to left of IVC
190
Name the 3 midline branches of the abdominal aorta
- coeliac trunk (foregut organs)
- superior mesenteric artery (midgut organs)
- inferior mesenteric artery (hindgut organs)
191
What do the lateral branches of the abdominal aorta supply?
- kidneys / adrenal glands
- gonads (ovaries / testes)
- body wall (posterolateral)
192
The abdominal aorta bifurcates into what?
The common iliacs
Which then further bifurcate to internal and external iliacs
193
Describe arterial anastomoses
- there exists arterial anastomoses between the branches of the SMA and the IMA
- predominantly one artery called the marginal artery of Drummond
- depending on the health of these anastomotic vessels and the speed at which obstruction of a vessel occurs, these anastomoses could help prevent intestinal ischaemia
- by providing a collateral by which blood can travel
194
The inferior mesenteric artery supplies what?
- the hindgut organs
195
The internal iliac artery supplies what?
The remainder of the GI tract - after the pectinate line
196
Inferior vena cava role
- drains cleaned blood from the hepatic veins into the right atrium
197
Hepatic portal vein role
- drains blood from foregut, midgut and hindgut structure to the liver for first pass metabolism
198
Splenic vein role
- drains blood from foregut structure to hepatic portal vein
199
Superior mesenteric vein role
- drains blood from midgut structure to hepatic portal vein
200
Inferior mesenteric vein role
Drains blood from hindgut structures to splenic vein
201
Name the three clinically important sites of venous anastomosis between the systemic and portal venous systems
- distal end of oesophagus
- skin around umbilicus
- rectum / anal canal
202
What happens at the portal systemic anastomoses?
- at these sites, the presence of small collateral veins means blood can flow both ways
- either into the systemic or portal venous system
- there are no valves in these veins
- normally there is very little blood flow within these collateral veins
203
The control of the excretion of faeces is complex and requires what?
- a holding area (rectum); to store faeces until appropriate to defecate
- normal visceral afferent nerve fibres to sense fullness of the rectum
- functioning muscle sphincter around the distal end of the GU tract to respond to this fullness; to appropriately contract, preventing defecation and to relax allowing defecation
- normal cerebral function to control the appropriate time to defecate
204
Faecal continence can be affected by what?
- medications
- natural age related degeneration of nerve innervation of muscle, affected by consistency of stool
- neurological pathology
- during childbirth
205
When does the sigmoid colon become the rectum?
Anterior to S3
he rectosigmoid junction
206
When does the rectum become anal canal?
Anterior to the tip of the coccyx just prior to passing through the levatorani muscle
207
What is the anus?
The distal end of the anal canal and is the orifice which faeces pass through
208
Describe the rectum
- the rectal ampulla lies immediately superior to the levatorani muscle
- its walls can relax to accommodate faecal material
- functioning muscles and muscle sphincter are required to hold faeces in the ampulla until appropriate to defecate
209
Describe the anatomical relationships to the rectum
- peritoneum covers the superior rectum
- rectouterine / rectovesical pouch lie anterior to the superior rectum
- in the male, the prostate gland lies anterior to the inferior rectum
- in the female, the vagina and cervix lies anterior to the inferior / middle rectum
210
Describe the levator ani muscles
- forms most of the pelvic diaphragm
- together with fascial coverings
- made up of a number of smaller muscles
- forms most of floor of pelvis
- forms most of roof of peritoneum
- skeletal muscle
- provides continual support for the pelvic organs, tonically contracted most of the time
- reflexively contracts further during increase in intra-abdominal pressure eg. coughing, sneezing
- the muscle must relax to allow defecation and urination to occur
- supplied by the nerve to levatorani ( a branch of the sacral plexus) and pudendal
211
Describe the puborectalis
- part of the levatorani muscle
- particularly important for maintaining faecal continence
- contraction of this muscle decreases the anorectal angle, acting like a sphincter
- this is a skeletal muscle; contraction is under voluntary control
- when the rectal ampulla is relaxed and filled with faeces, voluntary contraction of this muscle will help to maintain continence
212
Describe the two anal sphincters
- 1 internal, smooth muscle
| - 1 external, skeletal muscle
213
Describe the pudendal nerve
- branch of sacral plxus
- S2, S3, S4 anterior rami
- supplies external anal sphincter
- exits pelvis via greater sciatic foramen
- quickly enter perineum via lesser sciatic foramen
- branches to supply structure of perineum
214
Describe pudendal nerve or sphincter damage
- during labour
- the branches of the pudendal nerve could be stretched
- resultant stretch of the nerve fibres
- fibres within the puborectalis or external anal sphincter muscle could be torn
- results in weakened muscle
- faecal incontinence could result
215
Describe the pectinate line
- marks the junction between the part of the embryo which formed the GI tract (endoderm) and the part that formed the skin (ectoderm)
- arterial supply, venous drainage, lymphatic drainage and nerve supply differ above and below the pectinate line
216
Describe supplies above the pectinate line
- nerve supply; autonomic
- arterial supply; from inferior mesenteric artery
- venous drainage; to portal venous system (IMV)
- lymphatic drainage inferior mesenteric nodes (internal iliac nodes)
217
Describe supplies below the pectinate line
- nerve supply; somatic, pudendal
- arterial supply; from internal iliac artery
- venous drainage; to systemic venous system (internal iliac)
- lymphatic drainage; superficial inguinal nodes
218
Describe the lymphatics of the pelvis
- lymph vessels tend to lie alongside the arteries
219
Name the main groups of lymph nodes draining the pelvic organs
- internal iliac (draining inferior pelvic structures)
- external iliac (draining lower limb, and more superior pelvic structures)
- common iliac (drain the lymph from the external and internal iliac nodes)
- lymph draining through the common iliac nodes then drains to the lumbar nodes
220
Describe blood supply to rectum and anal canal
- the inferior mesenteric artery supplies the hindgut organs
- the hindgut extends to the proximal half of the anal canal (the pectinate line)
- the remainder of the GI tract is supplied by the internal iliac artery
- there is a degree of anastomoses between these vessels
221
Describe the venous drainage from rectum and anal canal
- the inferior mesenteric vein drains the hindgut organs; above pectinate line, portal venous system
- the internal iliac vein drains below pectinate line, systemic venous system
222
Describe rectal varices
- form in relation to portal hypertension
| - dilatation of collateral veins between portal and systemic venous systems
223
Describe haemorrhoids
- prolapses of the rectal venous plexuses
- their development is not related to portal hypertension
- raised pressure eg. chronic constipation, straining, pregnancy
224
Describe the ischioanal fossae
- right and left
- lies on each side of the anal canal
- filled with fat and loose connective tissue
- the two fossae communicate with each other posteriorly
- an infection within the ischioanal fossa is called an ischioanal abscess
