Cardiac Embryology Phases

What does this image represent? Identify the week of development.

• A single endocardial heart tube

• The second phase of the hearts development

• Week 3

What do the TRUNCUS ARTERIOSUS and the SINUS VENOSUS eventually become?

• TRUNCUS ARTERIOSUS 🡪 the distal portion of bulbus cordis will form AO & main PA

• SINUS VENOSUS 🡪 forms SVC, IVC, PV4, CS, oblique vein of LV, posterior portion of RA & LA

What does the image represent and what are the two layers present? Identify the week of development.

• The first part of the heart development

1. inner, thinner layer - endocardium

2. outer, thicker layer - myocardium

• Prior to week 3

What does the image represent and what is occurring in this image? Identify the week of development.

• The third phase of the heart’s development

• S-shaped loop, normally folds to the right (known as D-looping)

• Week 4

What does the image represent? Identify the week of development.

• The fourth phase of the hearts development

• Note the center of the endocardial cushion

• Week 4.

What does the image represent? What occurs during this phase? Identify the week of development.

• The fifth phase of the heart’s development

• Septum primum reaches endocardial cushions & closes ostium primum

• Week 5

What does the image represent? What occurs during this phase? Identify the week of development.

• The sixth phase of the hearts development

• The conus cordis forms 🡪 RVOT & LVOT

• Week 5

What does the image represent? What occurs during this phase? Identify the week of development.

• The seventh phase of the heart’s development

• LV communicates with RV via 2 routes

1) primary interventricular foramen

2) secondary interventricular foramen🡪 membranous IVS

• Week 5

What does the image represent? What occurs during this phase? Identify the week of development.

• The eighth phase of the heart’s development

• At birth/first breath - LAP increases (doubles) forcing septum primum against septum secundum—closing the FO

• Together, septum primum & septum secundum 🡪 form IAS

• Week 7

What does the image represent? What occurs during this phase? Identify the week of development.

• The ninth and final phase of cardiac development

• Bulbar ridges directly involved in rotation & division of truncus arteriosus into AO & main PA 

• Fetal circulation is in place! Final requirement is growth.

• Week 7

Put the images in order.

Order: H,A,C,E,B,I,F,G,D

Identify the first three phases of development and the week.

H- Prior to week 3

A- Week 3

C- Week 4

Identify the 4th, 5th, and 6th phases of development and the week.

E- Week 4

B- Week 5

I- Week 5

Identify the final three phases of development and the week.

F- Week 5

G- Week 7

D- Week 7