S4Anatomy Flashcards
Which vertebral level is the suprasternal notch located?
T2/T3
Which vertebral level is the thyroid notch located?
C4
Which vertebral level is the lower border of cricoid cartilage located?
C6
Which vertebral level is the hyoid bone located?
C3
Describe the location of the lateral lobe of the thyroid?
The apex extends up to the oblique line of the thyroid cartilage and the base to the level of the fourth or fifth tracheal ring.
Describe the location of the Isthmus of the thyroid?
Crosses anterior to the 2nd, 3rd and 4th tracheal ring.
Describe the location of the Pyramidal lobe of the thyroid?
Projects upwards from the isthmus to the left of the midline.
What encloses the thyroid gland?
A thin connective tissue capsule, from which, septa project into the gland. A loose connective tissue sheath surrounds the gland and the capsule.
From which layer of cervical fascia is this sheath derived?
Pretracheal fascia
Where does the superior thyroid artery arise from?
External Carotid artery
Which nerve runs alongside the superior thyroid artery?
Superior laryngeal nerve
The inferior thyroid artery arises from the thyrocervical trunk. Which vessel does the thyrocervical trunk arise from?
Subclavian artery
Which nerve crosses the inferior thyroid artery?
recurrent laryngeal nerve
What supplies arterial blood to the thymus gland?
the superior and inferior thyroid arteries; the superior thyroid artery supplies the upper pole of each lobe whilst the inferior thyroid artery supplies the posteroinferior aspect
In 10% of the population, a third artery contributes to blood supply of the thyroid. What is it and where does it arise from?
Thyroid ima artery
It may arise from the brachiocephalic trunk or arch of aorta, less commonly from the right common carotid, subclavian or internal thoracic arteries.
Describe the venous drainage of the thyroid.
Three pairs of veins, the superior, middle and inferior thyroid veins drain the superior, middle and inferior parts of the thyroid gland respectively. These vessels form a plexus of nerves on the anterior aspect of the gland.
Into which vein do the superior and middle thyroid veins empty?
Internal jugular vein
Into which vein does the inferior thyroid vein empty?
Brachiocephalic vein
Where does the lymph vessels of the thyroid drain into?
These vessels drain into the prelaryngeal, pretracheal and paratracheal nodes. Efferent vessels from these nodes go to the deep cervical nodes.
What type of innervation does the thyroid receive?
Sympathetic innervation
Where do post ganglionic fibres of the thyroid arise and where do the pass through?
Post ganglionic sympathetic fibres arise in the superior, middle and inferior cervical ganglia and pass through the cardiac, superior and inferior thyroid plexuses to reach the gland.
What type of information is transmitted in Post ganglionic sympathetic fibres of the thyroid?
Vasomotor
What is a thyroid goitre?
An enlargement of the thyroid gland which may occur due to over activity or underactivity of the gland
Which directions does the thyroid gland spread when it is enlarged?
Anterior
Inferior
Lateral
Posterior
What prevents the thyroid from enlarging the superior direction?
The superior attachments of sternothyroid and sternhyoid muscles
What structures may be compressed by a goitre?
Oesophagus
Trachea
Recurrent Laryngeal Nerves
How does the thyroid develop?
It develops from a thickening on the floor of the embryonic pharynx in the developing tongue.
A diverticulum develops from this thickening forming the thyroglossal duct.
The thyroglossal duct elongates and its distal end becomes bi-lobed and proliferates into the thyroid gland.
The thyroid gland descends through the neck anterior to the hyoid bone.
At seven weeks the gland reaches its adult position.
The thyroglossal duct subsequently degenerates but a pit remains on the dorsum of the tongue marking its site of origin.
What is the name of the pit, on the dorsum of the tongue, which marks the site of origin of the thyroglossal duct?
Foramen caecum
When do Thyroglossal duct cysts occur? What are the symptoms and where are the cysts located?
When the duct fails to degenerate leaving a persistent connection between the back of the tongue and the thyroid gland.
They can be asymptomatic but fluid may accumulate in small pockets and infection may occur.
The cysts are often located close to the hyoid bone.
Their position in the neck will rise if the patient sticks their tongue out.
When does accessory thyroid tissue occur and where can it be found?
Accessory thyroid tissue may present anywhere along the route of descent of the thyroglossal duct.
It occurs when isolated pockets of glandular tissue of the thyroglossal duct fails to degenerate.
How do pyramidal lobes of the thymus develop? Where are they, and how many people have them?
They develop from the remnants of the epithelium and connective tissue of the thyroglossal duct.
They are present in approximately 50% of the population. These lobes extend upwards from the isthmus usually to the left of the median plane
How does Ectopic thyroid glands occur?
Ectopic thyroid glands occur when the gland fails to descend. In incomplete descent the gland will be located high in the neck. Rarely, the gland may fail to leave the tongue and a lingual thyroid develops.
Describe the histology of the thyroid gland
The thyroid gland consists of numerous rounded follicles containing colloid. The walls of each follicle consist of a single layer of cuboidal epithelial cells which secrete the colloid into the central colloid lake. The colloid is iodinated whilst it is within the colloid lake forming triiodothyronine (T3) and thyroxine (T4).
A second cell type are also present in the thyroid gland. They are called parafollicular or C cells and they contribute to 2% of the cells within the gland.
What do parafollicular cells secrete?
Calcitonin
What are the differences between active and inactive follicular cells?
In the inactive state the follicular cells are cuboidal in shape and have round nuclei. The cells appear taller and more columnar in shape when they are active and their nuclei appear paler.
T/F
The parathyroid glands are embedded into the posterior aspect of the thyroid gland, they lie deep to the fascial sheath.
True
T/F
The position of the superior parathyroid glands is more variable that that of the inferior ones
True
T/F
The superior parathyroid glands usually lie below the point where the superior thyroid vessels enter the thyroid gland.
True
T/F
The inferior parathyroid glands may be located in the superior mediastinum
True
T/F
The parathyroid glands are most commonly supplied by the inferior thyroid artery.
True
T/F
The parathyroid glands are innervated by postganglionic sympathetic fibres from the superior or middle cervical ganglia
True
T/F
The sympathetic nervous system provides secretomotor fibres to the parathyroid gland
False
The fascial sheath that surrounds the parotid gland is derived from where?
investing layer of fascia
Parasympathetic innervation to parotid gland is provided by which nerve?
glossopharyngeal nerve
The nerve cell bodies of postganglionic fibres that supply the sublingual gland are located where?
Pterygopalatine ganglion
What runs through the parotid gland?
External carotid artery
facial nerve
superficial temporal artery
superficial temporal artery
What runs through the parotid gland?
External carotid artery
facial nerve
superficial temporal artery
superficial temporal artery
List components of pancreatic juice
Chymotripsinogen Trypsinogen Amylase Ribonuclease Lipase Elatase
List secretions of the islets of Langerhans
Vasoactive intestinal polypeptide
Glucagon
Somatostatin
Insulin
Where does the pancreas lie?
Retroperitoneally in both the right and left upper quadrants of the abdomen
Which anatomical plane does the pancreas lie across?
Transoyloric
Describe the location of the head of the pancreas.
Expanded part of the gland which lies in the concavity of the duodenum
Describe the location of the ucinate process of the pancreas.
The part of the head which extends behind the superior mesenteric vessels
Describe the location of the neck of the pancreas.
The hepatic portal vein is formed posterior to this constricted part of the gland
Describe the location of the body of the pancreas.
Runs upwards to the left, crossing the midline
Describe the location of the tail of the pancreas.
Passes between the layers of the splenorenal ligament and contacts the hilum of the spleen
Describe the main pancreatic duct
Extends from the tail to the head of the pancreas
Receives many tributaries and increases in diameter
Unites with the bile duct to form the hepatopancreatic ampulla
Enters the duodenum at the major duodenal papilla
Describe the accessory pancreatic duct
Drains the upper part of the head of pancreas
May communicate with the main duct
Opens into duodenum at the minor duodenal papilla
Occasionally absent
How is the flow of bile and pancreatic juice into the duodenum controlled?
The hepatopancreatic sphincter, this sphincter also prevents reflux of duodenal content back into the pancreatic and bile ducts.
From which vessel does the gastroduodenal artery arise?
-
From which vessel does the inferior pancreaticoduodenal artery arise?
Superior mesenteric artery
From which vessel does the splenic artery arise?
-
What supplies the head of the pancreas?
The superior and inferior pancreaticoduodenal arteries
What supplies the rest of the pancreas?
Splenic artery
What drains the head of the pancreas?
Superior and inferior pancreaticoduodenal veins
What drains the rest of the pancreas?
Splenic vein
Which vein does the inferior pancreaticoduodenal vein drain into?
Superior mesenteric vein
Which vein is formed by the union of the superior mesenteric and splenic veins?
Hepatic portal vein
Which vein does the superior pancreaticoduodenal vein drain into?
-
How much does the liver weigh approximately?
1.5kg
Which abdominal regions is a healthy liver located?
R. Hypochondriac
Epigastrium
L/ Hypochondriac
What is the difference between diaphragmatic and visceral surfaces on the liver?
The diaphragmatic surface is smooth as it is moulded by the under surface of the diaphragm. In contrast the visceral surface is irregular as it is in contact with the irregular shaped viscera.
What is the falciform ligament?
A double fold of peritoneum that connects anterior & superior surfaces of the liver to the anterior abdominal wall.
What is the Ligamentum teres (round ligament)?
Remnant of the umbilical vein, it runs in the free edge of the falciform ligament.
What is the Ligamentum venosum?
Remnant of the ductus venosus, it is attached to the portal vein and the IVC.
What is the Coronary ligament?
A reflection of visceral peritoneum that extends from the posterior surface of the liver onto the diaphragm.
What is the right and left triangular ligament?
The left and right extremity of the coronary ligament
What is the hepatogastric ligament?
The part of the lesser omentum which extends from liver to lesser curvature of stomach.
What is the hepatoduodenal ligament?
The free border of the lesser omentum, it contains the bile duct, portal vein and hepatic artery.
Posteriorly, the liver looks like it has a letter H on it. What forms the H?
Two sagittal fissures joined together in the middle by the porta hepatis.
Which structure lies in the fossa that forms the anterior part of the right sagittal fissure?
-
Which structure lies in the groove that forms the posterior part of the right sagittal fissure?
-
Which structure lies in the groove that forms the posterior part of the left sagittal fissure?
-
Which structure lies in the groove that forms the anterior part of the left sagittal fissure?
-
What is the porta hepatis?
The site where structures enter or leave the liver
What can be found in the porta hepatis?
Hepatic arteries Hepatic ducts Portal veins Lymphatics Autonomic fibres
What is the bare area of the liver?
a small area posteriorly where it comes into direct contact with the diaphragm.
What is the basic structural unit of the liver?
Liver lobule
Describe the histology of the liver?
Each lobule is hexagonal in shape and consists of plates of hepatocytes radiating towards a central vein. Vascular channels, the liver sinusoids, are placed between the plates of hepatocytes. They convey blood from the periphery of the lobule to the central vein. A portal triad is located at each angle of the hexagonal lobule.
What is in the portal triad?
Each lobule is hexagonal in shape and consists of plates of hepatocytes radiating towards a central vein. Vascular channels, the liver sinusoids, are placed between the plates of hepatocytes. They convey blood from the periphery of the lobule to the central vein. A portal triad is located at each angle of the hexagonal lobule.
What percentage of blood to the liver is delivered by the hepatic artery proper?
20-25%
From which vessel does the hepatic artery proper (hepatic artery) arise?
Common hepatic
What percentage of blood is delivered to the liver from the portal vein?
75-80%
Which two veins unit to form the portal vein?
Splenic and superior mesenteric
Describe the blood flow through the liver
Branches of hepatic artery and portal vein enter the portal triad
Blood is conveyed through the liver sinusoid and drains into the central vein.
Blood drains into the right and left hepatic veins
These vessels drain into the inferior vena cava
Why are anastomoses between the hepatic portal system and systemic circulation important?
If portal circulation through the liver is obstructed blood can return to the heart via the systemic circulation. As the portal vein and its tributaries have no valves the blood can flow in a retrograde direction to the IVC.
Describe the inferior oesophagus anastomose site
Lower third drains via left gastric vein into portal vein - middle third drains into azygos vein.
Describe the Anal canal anastomose site
Superior rectal veins drain into portal system - middle and inferior rectal veins drain into internal iliac and internal pudendal veins.
Describe the Secondary retroperitoneal structures anastomose site
Superior mesenteric, inferior mesenteric and splenic vessels drain into portal system - renal, lumbar and phrenic veins drain into IVC.
Describe the Anterior abdominal wall anastomose site
Paraumbilical veins drain into portal system – superficial veins of abdomen drain into axillary or femoral veins
How much of total lymph production is from the liver?
up to half