GI

Question 1

At which part of the duodenum does the foregut end?

Answer 1

The junction between the second and third part.

Question 2

Which layer/s of the trilaminar disk is the primitive gut tube formed from?

Answer 2

Endoderm and visceral mesoderm.

Question 3

What are the pharyngeal arches formed from?

Answer 3

Masses of mesenchymal tissue (connective tissue derived from mesoderm) which are invaded by cranial neural crest cells.

Question 4

What is the difference between the pharyngeal clefts and the pharyngeal pouches?

Answer 4

Clefts are the external parts which are covered with endoderm.
Pouches are the internal parts which are covered with ectoderm.

Question 5

What bones and muscles does the first pharyngeal arch give rise to?
What is its innervation?

Answer 5

MUSCLES:
mastication, tensor tympani, digastric, mylohyoid

BONES:
maxilla, mandible, incus, malleus

INNERVATION = MANDIBULAR BRANCH OF TRIGEMINAL NERVE (CNV3)

Question 6

What bones and muscles does the second pharyngeal arch give rise to?
What is its innervation?

Answer 6

MUSCLES:
Facial expression, stapedius, stylohyoid

BONES:
stapes, styloid and lesser horn of hyoid cartilage

INNERVATION = FACIAL NERVE (CNVII)

Question 7

What bones and muscles does the third pharyngeal arch give rise to?
What is its innervation?

Answer 7

MUSCLES:
stylopharyngeus

BONES:
body and greater horn of hyoid cartilage

INNERVATION = GLOSSOPHARYNGEAL NERVE (CNIX)

Question 8

What bones and muscles does the fourth pharyngeal arch give rise to?
What is its innervation?

Answer 8

MUSCLES:
cricothyroid

BONES:
thyroid cartilage and epiglottic cartilage

INNERVATION = EXTERNAL BRANCH OF SUPERIOR LARYNGEAL NERVE (CNX)

Question 9

What bones and muscles does the fifth pharyngeal arch give rise to?
What is its innervation?

Answer 9

THERE ARE NO FIFTH ARCHES

Question 10

What bones and muscles does the sixth pharyngeal arch give rise to?
What is its innervation?

Answer 10

MUSCLES:
intrinsic muscles of the larynx (except cricothyroid)

BONES:
cricoid cartilage, arytenoid cartilages, corniculate and cuneiform cartilages

INNERVATION = RECURRENT LARYNGEAL NERVE (CNX)

Question 11

Define ligament, in terms of the gastrointestinal system.

Answer 11

Double layer of peritoneum which pass from one organ to another, or from one organ to the body wall.

Question 12

Describe the rotation of the stomach.

Answer 12

During the 7th week the stomach rotates 90 degrees clockwise around a longitudinal axis.

Question 13

What initiates swallowing?

Answer 13

Pressure receptors in the walls of the pharynx.

Question 14

Which nerve innervates the pharyngeal constrictor muscles?

Answer 14

Vagus nerve (CNX)

Question 15

Which type of muscle forms the upper oesophageal sphincter?

Answer 15

Skeletal muscle

Question 16

Briefly describe the gag reflex.

Answer 16

Irritation of the oropharynx at the back of the tongue stimulates the glossopharyngeal nerve (CNIX).
Vagus nerve (CNX) causes reflex elevation of the pharynx. This is often followed by vomiting.

Question 17

What is an alternative name for the parotid duct?

Answer 17

Stenson’s duct

Question 18

What are the surface markings of the parotid gland?

Answer 18

Zygomatic arch
Sternocleidomastoid
Ramus of mandible

Question 19

What muscle does the parotid duct cross in front of?

Answer 19

Masseter muscle

Question 20

What is an alternative name for the submandibular duct?

Answer 20

Wharton’s duct

Question 21

Which muscle is intimately related to the submandibular gland?

Answer 21

Mylohyoid

Question 22

Describe the drainage of the sublingual gland.

Answer 22

Drains into Wharton’s duct as well as small ducts that enter directly into the floor of the mouth.

Question 23

What are Von Ebner’s glands and where are they found?

Answer 23

Minor SEROUS salivary glands underlying the circumvallate papillae.

Question 24

Are the minor salivary glands serous or mucinous?

Answer 24

They are all mucinous except for the serous glands of Von Ebner.

Question 25

Where are mucous cells in the stomach located?

Answer 25

At the entrance to the glands.

Question 26

How does the muscular wall of the stomach compare in the body and antrum?

Answer 26

It is much thinner in the body and thicker in the antrum.

Question 27

How do gastrin and histamine increase HCl secretion?

Answer 27

They increase the number of H+/K+ ATPase pumps in the parietal cell membrane.

Question 28

How do proteins stimulate gastric acid secretion?

Answer 28

They act as a buffer, accepting H+ ions, therefore making the pH in the stomach increase.

Question 29

Which part of the intestines absorbs the most water?

Answer 29

Jejunum

Question 30

What percentage of ingested fluid is secreted in stools?

Answer 30

2%

Question 31

Are the epithelial membranes in the small intestine permeable or impermeable to water?

Answer 31

Very permeable

Question 32

Describe the absorption of sodium in the intestines.

Answer 32

Actively transported in the jejunum and ileum.

Actively transported in the colon.

Question 33

Describe the absorption of potassium in the intestines.

Answer 33

Passive diffusion in the colon.

Question 34

What is the significance of phospholipids being amphipathic?

Answer 34

They can emulsify lipids.

Question 35

What releases free fatty acids from chylomicrons at adipocytes?

Answer 35

Lipoprotein lipase

Question 36

Where are fat soluble vitamins absorbed?

Answer 36

Ileum

Question 37

How are most water-soluble vitamins absorbed?

Answer 37

Diffusion or mediated transport in the jejunum.

NOT B12

Question 38

Where does most carbohydrate absorption take place?

Answer 38

Duodenum

Question 39

What do fatty acids combine with in hepatocytes and adipocytes to form triglycerides?

Answer 39

a-glycerolphosphate