Development of Arteries and Veins Flashcards

1
Q

Blood vessel formation

A
  • Extraembryonic vasculogenesis
  • Intraembryonic vasculogenesis
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2
Q

Extraembryonic vasculogenesis

A
  • vessels forming within the membranes
  • Mammals: blood vessels established in yolk sac (even without yolk) and in the allantois
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3
Q

Intraembryonic vasculogenesis

A

vessels forming within the embryo

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4
Q

Processes required for blood vessel development

A
  1. vascuologenesis
  2. Angiogenesis
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5
Q

Vasculogenesis

A
  • The initial formation of blood vessels
  • A network of blood vessels is formed de novo from the lateral plate mesoderm
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6
Q

Angiogenesis

A

The sprouting of blood vessels from existing ones and remodeling of vascular beds

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7
Q

Hemangioblasts and vasculogenesis

A
  • Hemangioblasts are cells more posterior to the cardiogenic or heart fields. Within the splanchnic mesoderm
  • The hemangioblasts condense into aggregates called blood islands
  • They are the precursors for both blood cells and blood vessels in the yolk sac and allantois
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8
Q

Angioblasts

A

Precursors for blood vessels within embryo

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9
Q

Steps of extra-embryonic vasculogenesis (yolk sac)

A
  1. Cell formation
    - The inner cells of the blood islands (hemangioblasts) become Hematopoietic stem cells for blood cell formation
    - The outer cells become angioblasts (progenitor cells for blood vessels)
  2. Angioblasts will proliferate and differentiate into endothelial cells to line the new blood vessels and these endothelial cells will form tubes and connect to form a capillary plexus or network
  3. Lumen formation from creation and fusion of vacuoles created by endocytosis
  4. Results in vitelline and umbilical veins
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10
Q

Importance of vasculogenesis in yolk sac

A

Important to produce vessels that will bring nutrients to embryo, aid gas exchange, and bring blood cells to heart for distribution
- Vitelline and umbilical veins

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11
Q

Steps of intra-embryonic vasculogenesis

A
  1. Vascular networks arise from individual angioblast progenitor cells originating in most mesodermal tissues of body
  2. Developing organs produce paracrine factors that induce blood vessel formation in their own mesenchyme. This allows the developing vessel or capillary network to have specific properties for that organ or group of organs
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12
Q

Arterial vs. venous system

A

Arteries and veins do differ from one another despite originating from same endothelial precursor (angioblasts). Arterial or venous identity of endothelial cells is established very early on before angiogenesis sets in and before onset of circulation
- 2 types of endothelial cells are present within the primary vascular plexus. Allows for distinction, anastomosis (joining together) or arteries and veins, and fusion of capillaries to make larger vessels

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13
Q

Arterial programming

A
  • Notch stimulation
  • Ephrin B2
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14
Q

Venous programming

A
  • Less notch stimulation
  • Ephrin B4
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15
Q

Arterial system

A
  1. Folding places heart with pericardial cavity and bends developing aortae
    - Anterior extensions become 2 ventral aortae
    - Posterior extensions join with developing venous system
    - Dorsal part become dorsal aortae
  2. Aortic arches form
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16
Q

Aortic arches

A
  1. Cranial-caudal body folding results in cranial parts of dorsal aortae bending and aortic arches forming lateral to foregut
    - Aortic arches form from mesoderm within masses called the pharyngeal arches. Aortic arches link the aortic sac and paired dorsal aortae
  2. Aortic arches develop sequentially not all at once
17
Q

Derivatives of aortic arches

A

Angiogenesis occurs- remodelling or the arches to create vessels

18
Q

What does the 1st aortic arch become?

A
  • Maxillary artery
19
Q

What does the 2nd aortic arch become?

A

Stapedial or hyoid arteries

20
Q

What does the 3rd aortic arch become?

A

Ventral: common carotid artery

Dorsal: internal carotid artery

21
Q

What does the 4th aortic arch become?

A

Part of the arch of aorta

22
Q

What does the 5th aortic arch become?

A
  • Rudimentary in horse and pig
  • Never develops in cattle
23
Q

What does the 6th aortic arch become?

A
  • Part of the left pulmonary artery
    -Ductus arteriosus
24
Q

Dorsal aortae

A

Extends caudally and gives rise to the dorsal, lateral, and ventral segmental arteries

25
Q

Dorsal segmented arteries

A

Dorsal segmented arteries are paired; found in each segment from cranial somites to the sacral region.
- Dorsally: Will give rise to dorsal or spinal branches to supply neural tube and derivatives
- Ventrally: will supply the ventral body wall and become intercostal arteries in thorax and lumbar arteries in abdomen

26
Q

Aorta derivatives in cervical region

A

Cervical region: 7 dorsal pairs of segmented arteries form; 6 disconnect from aorta but unite with seventh that remains connected
- Form paired vertebral arteries which extend cranially and fuse to form a single basilary artery to supply the brainstem

27
Q

Aorta derivatives in caudal region

A

Lateral segmental arteries develop from unpaired part of the dorsal aorta and supply organs developing from intermediate mesoderm
- Mesonephric, adrenal, and genital ridge arteries form during development and become the ovarian, testicular, and adrenal arteries in adult
- Renal arteries also form but only with development of metanephrons

28
Q

Aorta derivatives in ventral region

A
  • Ventral segmental arteries are affiliated with yolk sac and allantois
    o Vitalline arteries arise from unpaired part of aorta and supply yolk sac
  • When the yolk sac disappears, the left vitelline artery will disappear and the right vitelline artery becomes the coeliac artery and superior mesenteric artery
  • The caudal pair of ventral segmented arteries develops from the still unpaired portion of aorta in that region and they form the umbilical arteries that supply the allantois and placenta (will eventually become iliac artery)
29
Q

Ductus arteriosus

A

Short vessel that connects fetal pulmonary artery to the aorta allowing oxygenated blood to bypass the pulmonary circulation

30
Q

Circulation before birth

A
  • Oxygenated blood travels from placenta via the left umbilical vein to the liver where most bypasses the hepatic sinusoids via the ductus venosus and enters the caudal vena cava. (A small amount does mix with deoxygenated blood from portal vein and enters the vena cava)
  • Oxygenation of blood entering the right atrium from vena cava is high (although slightly reduced from visit to liver) and bypasses pulmonary system through foramen
  • Oxygenated blood will leave through aortic arch, and the coronary arteries and brachiocephalic trunk are the first branches which means that the heart musculature and brain will receive the most oxygenated blood
31
Q

Oxygenated blood that does not bypass pulmonary system

A
  • Will go to the right ventricle and mix with deoxygenated blood that is returning from the head
  • Blood will then be pumped to the pulmonary trunk but there is resistance due to non-functioning lungs. So this blood will then pass through ductus arteriosus to the aorta and most of it will return to the placenta via umbilical arteries for re-oxygenation
32
Q

Circulation prior to birth

A
  • The umbilical arteries contract to prevent passage of blood to placenta and umbilical veins will contract at birth to force blood in placenta into the circulation of the newborn
  • Contraction of ductus venosus also occurs
  • Musculature of ductus arteriosus contracts to close the shunt because lungs are now functional
  • Closure of foramen ovale begins
33
Q

What happens to the umbilical artery remnants?

A

Reorganized into round ligaments of the bladder

34
Q

What happens to the left umbilical vein after birth?

A

Reorganized into round ligaments of the liver

35
Q

Patent ductus arteriosus (PDA)

A

Can lead to rising pressure in the aorta and left ventricle forcing blood from aorta into the pulmonary artery and sometimes the right ventricle
- Results in cardiac output having to be increases to maintain circulation for normal function
- May present as machine-like or continuous murmur on auscultation over region of aortic and pulmonary valves