Lecture 15: Aortic Arches And Veins

Question 1

What are the components of the vertebrate cardiovascular system?

Answer 1

Components:

• Muscular pump:
• Heart
• Vessels carrying blood away from the heart:
• Arteries: Note that whether they are carrying oxygenated or deoxygenated blood is immaterial.
• Vessels carrying blood toward the heart:
• Veins
• A series of connecting vessels associated with the pharyngeal arches:
• Aortic arches
• See Slide 6

Question 2

Describe the aortic arch

Answer 2

• Aortic arches form during embryonic development.
• Typically, there are six pairs of aortic arches.
• The embryonic pattern is relatively unchanged in fishes but is considerably modified in tetrapods.
• Six pairs of aortic arches connect: the paired dorsal aortae to the ventral aorta.
• In fishes aortic arches are interrupted by the capillary beds of gills.

Question 3

Describe the aortic arch pattern in sharks

Answer 3

• First aortic arch pair is lost.
• Afferent and efferent branchials carry blood to and from gills.
• Afferent and efferent spiraculars carry blood to first pair of gills (spiracles).
• Pseudobranch.
• Arteries off efferent aortic arches:
• Hypobranchials
• External carotids
• In teleosts:
• First aortic arch pair is lost.
• Similar to pattern in shark.

Question 4

Describe the aortic arch patterns of lungfish

Answer 4

• Similar to that in fishes.
• Pulmonary artery develops from arch VI.
• Arches III and IV lose their capillary beds

Question 5

Describe aortic arch formation/fate

Answer 5

• Aortic arch pattern in non-mammalian tetrapods:
• Typically, first and second pairs of aortic arches form but later degenerate.
• Third pair of aortic arches form the internal carotids and common carotids.
• Note that external carotids are the cranial extensions of the paired ventral aortae cranial to the third arches.
• Fourth pair of aortic arches form the paired aortic arches.
• Fifth pair of arches degenerate.
• Sixth pair of arches become associated with the pulmonary system

Question 6

Describe the aortic arch pattern in Amphibians and Reptiles

Answer 6

• Loss of arch pairs I, II, V.
• Loss of capillary beds in remainder of arches.
• Arch pair VI form pulmonary arteries.
• Arch pair IV form systemic arches.
• Arch pair III associated with carotid system.
• Ductus caroticus.

Question 7

Describe the aortic arch pattern in Birds

Answer 7

• Loss of arch pairs I, II, V.
• Loss of left aortic arch IV.
• Right aortic arch IV becomes the systemic arch (arch of the aorta).
• Loss of ductus caroticus and ductus venosus.

Question 8

Describe the aortic arch pattern in mammalian embryos

Answer 8

• First and second pairs of aortic arches form but later degenerate.
• Third pair of aortic arches (plus dorsal aortae cranial to third arches) form the internal carotids.
• Note that external carotids are the cranial extensions of the paired ventral aortae cranial to the third arches.
• The common carotids are derived from the ventral aortae between the third and fourth aortic arches.
• Right fourth aortic arch forms the right subclavian artery.
• Left fourth aortic arch forms the aortic arch.
• Fifth pair of arches degenerate (Just barely form—only remnants).
• Sixth pair of arches become associated with the pulmonary system.

Question 9

Describe the aortic arch pattern in adult mammals

Answer 9

• Similar to pattern in birds.
• Left fourth aortic arch is retained as systemic arch (= aortic arch).
• Patent ductus venosus retained in fetus.
• See Slide 17

Question 10

Describe the 3 aortic branches and their components

Answer 10

1. Dorsal intersegmentals:
   - Cervical, thoracic (intercostals), lumbar intersegmentals
   - Subclavians
   - Iliac arteries
2. Lateral intersegmentals:
   - Mesonephric arteries
   - Adrenal arteries
   - Renal arteries
   - Gonadal Arteries
3. Ventral intersegmentals:
   * Vitelline vessels:
   - Celiac artery (trunk)
   - Superior/inferior mesenterics
   * Allantoic vessels:
   - Umbilical arteries

• See Slide 20

Question 11

Describe the dorsal aortic branch

Answer 11

The dorsal aorta branches are similar in all vertebrate groups.

• Paired visceral branches of the aorta:
• Renal arteries
• Gonadal arteries
• Unpaired visceral branches:
• Celiac trunk: In mammals, gives rise to the left gastric, common hepatic, and splenic arteries;
• Superior mesenteric: In humans, supplies the intestine and colon as far distal as the left colic flexure
• inferior mesenteric artery: Supplies the rest of the colon.
• See Slide 23-24

Question 12

Describe the basic venous pattern

Answer 12

• The venous system in fishes is similar to the basic vertebrate venous system and to the general vertebrate embryonic venous system.
• This basic system is bilaterally symmetrical and consists of:
• A pair of anterior cardinal veins which drain the cranial region
• A pair of jugular veins which drain the head
• A pair of posterior cardinal veins draining the posterior body
• A pair of lateral veins draining the lateral body walls
• A pair of vitelline veins from the yolk sac
• An unpaired subintestinal vein.
• On each side, the anterior and posterior cardinal veins empty into one of a pair of common cardinal veins.
• The paired common cardinals, jugulars, and vitelline veins all empty into the sinus venosus.

Question 13

Describe cardinal vein pairs, and the overall fate of the anterior cardinal veins.

Answer 13

• Cardinal vein pairs: Anterior, Posterior, and Common
• Fate of the anterior cardinal vein:
• Anterior cardinals form the internal jugulars.
• Connection (anastomosis) between the two is the left brachiocephalic vein.
• All blood from the head is shunted to the right and drained into the right cardinal vein –> Superior Vena Cava
• Both the anterior and the posterior pairs of cardinal veins empty into the paired common cardinals, which empty into the sinus venosus.
• See Slides 28 & 29

Question 14

Describe additional cardinal veins and the formation of the inferior vena cava

Answer 14

• Additional cardinal veins:
• Subcardinals
• Supracardinals
• Formation of the inferior vena cava:
• The inferior vena cava is built as a patchwork quilt asymmetrically from remnants of the following:
• • Vitelline vein
• • Subcardinals
• • Supracardinals
• • Iliacs
• See Slides 31, & 32

Question 15

What are the 3 portal systems?

Answer 15

• Portal systems are named according to the termination of the first vein in the series. The three portal systems include:
  1. Hepatic portal
• • Right vitelline = hepatic portal vein
• • Proximal vitelline veins = hepatic veins
    2. Renal portal
• • Proximal ends of posterior cardinals degenerate.
• • Distal ends of posterior cardinals carry blood to kidneys = renal portal veins.
• • Subcardinals return blood to sinus venosus.
    3. Hypophyseal portal system

Question 16

What is the definition of a portal system?

Answer 16

A system of veins that carries blood toward the heart but ends in a capillary bed in an organ other than the heart.

See Slide 36

Question 17

Describe the hepatic portal system

Answer 17

• The hepatic portal system is an unpaired system of veins developed from one of the vitelline veins.
• These veins carry oxygen-poor but nutrient rich blood from the digestive tract to the liver via the hepatic portal vein.
• The nutrients are processed in the liver in a variety of ways, and the nutrient-poor blood finally passes into the sinus venosus via the hepatic veins, which are the remnants of the proximal ends of the embryonic vitelline veins.
• Note that the hepatic veins are “traditional” veins. Do not confuse them with the hepatic portal vein.
• All vertebrates have a hepatic portal system.
• This system basically involves a disintegration of certain veins and an interruption of others with capillary beds.
• The right vitelline and right branch of the subintestinal veins disintegrate posterior to the liver.
• The left vitelline and part of the old subintestinal persist as the hepatic portal vein.
• This vein leads into the liver and breaks into capillaries.
• The hepatic veins are the anterior ends of the old vitelline veins.
• They lead from the liver to the sinus venosus.

Question 18

Describe the renal portal system

Answer 18

• In the formation of the renal portal system the postcardinal veins form capillary connections with the kidney.
• The renal portal system is built from a new pair of veins:
• • Subcardinals:
• – Provide an alternate path for blood flowing from the distal parts of the posterior cardinals and the caudal vein to the proximal parts of the posterior cardinals.
• – Subcardinals form between the two kidneys, pass anteriorly from the anal loop, and swing out to join the postcardinals anterior to the kidneys.
• – Subcardinals also develop capillary connections with the kidney.
• – Thus, blood may flow to the kidneys via a couple of routes.
• The subcardinals are not present in primitive mammals.
• Both the posterior cardinals and the subcardinals drain the kidneys.
• By eliminating the distal portion of each subcardinal and a middle element of each posterior cardinal, a new blood return pathway is created which forces all blood returning from the posterior part of the body into a capillary plexus in each kidney.
• From here blood enters the subcardinal remnants and finally terminates back into the posterior cardinals toward the heart.
• In this pattern, the distal parts of the posterior cardinals become the renal portal veins
• See Slide 41 and 43 (Less certain about what the objective for 43 is asking.