ANAT2341 Lab 4 - Early Cardiovascular Development

From Embryology
ANAT2341 Lab 4: Introduction | Implantation and Villi | Decidua and Cord | Abnormal Placenta | Cardiovascular | Online Assessment | Group Project

Early Circulation

Three components of early circulation

The vascular system of the embryo is formed from blood islands that appear in the extraembryonic mesoderm of the yolk sac and the embryonic mesoderm (primarily splanchnic mesoderm). Both of these clusters fuse together and extend, forming a vast network.

The early circulation has 3 components: Vitelline, Embryonic, Placental (each of these has its own system of arteries and veins).

  • Vitelline - the vitelline arteries branch off the dorsal aortas and enter the yolk sac, covering its entire surface. The vitelline veins return red blood cells from the capillary beds to the sinus venosus, posterior to the heart. The vitelline vessels eventually contribute to the portal system of the liver in the adult.
  • Embryonic - blood from the dorsal aorta enters intersegmental arteries, including the arteries of the pharyngeal arches. The blood returns to the heart via the anterior and posterior cardinal veins.
  • Placental - the umbilical arteries receive blood from the aorta. This is carried to the chorionic villi, where exchange occurs with the mother. Waste products are disposed of, nutrients and oxygen are collected, and then the umbilical veins convey the blood to the sinus venosus.


The heart develops from cardiogenic mesoderm, a region of splanchnic mesoderm lying above the buccopharyngeal membrane. Development begins in week 3 with the formation of a pair of heart tubes. These fuse and form a single tube in week 4, as a result of the embryonic folding processes that occur. As the heart grows, septation events occur, transforming it into a 4-chambered pump. Initially, the ventricles develop above the atria; however simultaneous growth and bending of the tube bring the structures into correct position. In humans, the heart begins to beat on day 22-23. (This will be covered in detail in a later Lab)

Heart Tube Fusion.jpg Heart Tube Segments.jpg

The embryo (Carnegie stage 10) heart tube

Human heart SEM1.jpg

Scanning electron micrograph images of the early human (day 21 to 25) embryonic heart tube. Note the anterior body wall has been removed exposing the pericardial cavity in which the heart tube lies.

Cardiovascular Movies

We will not be covering later heart development, including septation, in today's practical.

Week3 folding icon.jpg
 ‎‎Week 3
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Heart1 looping icon.jpg
 ‎‎Heart Looping
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Heart1 realign icon.jpg
 ‎‎Heart Realign
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Heart1 atrium icon.jpg
 ‎‎Atrial Septation
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Heart1 ventricle icon.jpg
 ‎‎Outflow Septation
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Systemic Circulation

Compare the mid-embryonic cardiovascular system with that existing at the end of embryonic development. Then follow blood flow through the embryo using the Stage 13 embryo cross-sections.

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Stage13 bloodflow.jpg

About Stage 13 Embryo Sections - This image is from a serial section of a 6mm CRL pig embryo with some features of the Stage 14 embryo. This embryo is approximately equal to the day 42 human embryo. Use these serial images to identify internal features and relationships that exist within the embryo at this stage. Then compare these images with the later features of the Carnegie stage 22 human embryo.

Links: Carnegie stage 13 - serial sections | Carnegie stage 13 | Embryo Serial Sections
Stage 13 image 099-icon.jpg
Stage 13 Serial unlabeled images

A1   A2   A3   A4   A5   A6   A7

B1   B2   B3   B4   B5   B6   B7

C1   C2   C3   C4   C5   C6   C7

D1   D2   D3   D4   D5   D6   D7

E1   E2   E3   E4   E5   E6   E7

F1   F2   F3   F4   F5   F6   F7

G1   G2   G3   G4   G5   G6   G7

Embryo Stage 13 Serial labeled images

A1L  A2L  A3L  A4L  A5L  A6L  A7L

B1L  B2L  B3L  B4L  B5L  B6L  B7L

C1L  C2L  C3L  C4L  C5L  C6L  C7L

D1L  D2L  D3L  D4L  D5L  D6L  D7L

E1L  E2L  E3L  E4L  E5L  E6L  E7L

F1L  F2L  F3L  F4L  F5L  F6L  F7L

G1L  G2L  G3L  G4L  G5L  G6L  G7L

ANAT2341 Lab 4: Introduction | Implantation and Villi | Decidua and Cord | Abnormal Placenta | Cardiovascular | Online Assessment | Group Project
ANAT2341 Course Timetable  
Week (Mon) Lecture 1 (Mon 1-2pm) Lecture 2 (Tue 3-4pm) Practical (Fri 1-3pm)
Week 2 (1 Aug) Introduction Fertilization Lab 1
Week 3 (8 Aug) Week 1 and 2 Week 3 Lab 2
Week 4 (15 Aug) Mesoderm Ectoderm Lab 3
Week 5 (22 Aug) Early Vascular Placenta Lab 4
Week 6 (29 Aug) Gastrointestinal Respiratory Lab 5
Week 7 (5 Sep) Head Neural Crest Lab 6
Week 8 (12 Sep) Musculoskeletal Limb Development Lab 7
Week 9 (19 Sep) Renal Genital Lab 8
Mid-semester break
Week 10 (3 Oct) Public Holiday Stem Cells Lab 9
Week 11 (10 Oct) Integumentary Endocrine Lab 10
Week 12 (17 Oct) Heart Sensory Lab 11
Week 13 (24 Oct) Fetal Birth and Revision Lab 12

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