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Fundamentals of Anatomy and Physiology: 6.11 Development of Blood Vessels and Foetal Circulation

Fundamentals of Anatomy and Physiology
6.11 Development of Blood Vessels and Foetal Circulation
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table of contents
  1. Cover
  2. Title Page
  3. Copyright
  4. Table Of Contents
  5. About the Authors
  6. Acknowledgments
  7. Preface
  8. Levels of Organisation, Homeostasis and Nomenclature
    1. 1.1 Overview of Anatomy and Physiology
    2. 1.2 Structural Organisation of the Human Body
    3. 1.3 Homeostasis
    4. 1.4 Anatomical Terminology
  9. Cells and Reproduction
    1. 2.1 Synthesis of Biological Macromolecules
    2. 2.2 Carbohydrates
    3. 2.3 Lipids
    4. 2.4 Protein
    5. 2.5 Nucleic Acid
    6. 2.6 The Cell Membrane
    7. 2.7 The Cytoplasm and Cellular Organelles
    8. 2.8 The Nucleus and DNA Replication
    9. 2.9 Protein Synthesis
    10. 2.10 Cell Growth and Division
    11. 2.11 Cellular Differentiation
  10. Tissues, Organs, Systems
    1. 3.1 Types of Tissues
    2. 3.2 Epithelial Tissue
    3. 3.3 Connective Tissue Supports and Protects
    4. 3.4 Muscle Tissue and Motion
    5. 3.5 Nervous Tissue Mediates Perception and Response
    6. 3.6 Tissue Injury and Ageing
  11. Integumentary System
    1. 4.1 Layers of the Skin
    2. 4.2 Accessory Structures of the Skin
    3. 4.3 Functions of the Integumentary System
    4. 4.4 Diseases, Disorders and Injuries of the Integumentary System
  12. Blood
    1. 5.1 An Overview of Blood
    2. 5.2 Production of the Formed Elements
    3. 5.3 Erythrocytes
    4. 5.4 Leukocytes and Platelets
    5. 5.5 Haemostasis
    6. 5.6 Blood Typing
  13. Cardiovascular System
    1. 6.1 Heart Anatomy
    2. 6.2 Cardiac Muscle and Electrical Activity
    3. 6.3 Cardiac Cycle
    4. 6.4 Cardiac Physiology
    5. 6.5 Development of the Heart
    6. 6.6 Structure and Function of Blood Vessels
    7. 6.7 Blood Flow, Blood Pressure and Resistance
    8. 6.8 Capillary Exchange
    9. 6.9 Homeostatic Regulation of the Vascular System
    10. 6.10 Circulatory Pathways
    11. 6.11 Development of Blood Vessels and Foetal Circulation
  14. Lymphatic System and Immunity
    1. 7.1 Anatomy of the Lymphatic and Immune Systems
    2. 7.2 Barrier Defences and the Innate Immune Response
    3. 7.3 The Adaptive Immune Response: T Lymphocytes and their Functional Types
    4. 7.4 The Adaptive Immune Response: B-Lymhocytes and Antibodies
    5. 7.5 The Immune Response Against Pathogens
    6. 7.6 Diseases Associated with Depressed or Overactive Immune Responses
    7. 7.7 Transplantation and Cancer Immunology
  15. Respiratory System
    1. 8.1 Organs and Structures of the Respiratory System
    2. 8.2 The Lungs
    3. 8.3 The Process of Breathing
    4. 8.4 Gas Exchange
    5. 8.5 Transport of Gases
    6. 8.6 Modifications in Respiratory Functions
    7. 8.7 Embryonic Development of the Respiratory System
  16. Muscle System
    1. 9.1 Overview of Muscle Tissues
    2. 9.2 Skeletal Muscle
    3. 9.3 Muscle Fibre Contraction and Relaxation
    4. 9.4 Nervous System Control of Muscle Tension
    5. 9.5 Types of Muscle Fibres
    6. 9.6 Exercise and Muscle Performance
    7. 9.7 Cardiac Muscle Tissue
    8. 9.8 Smooth Muscle
    9. 9.9 Development and Regeneration of Muscle Tissue
  17. Skeletal System
    1. 10.1 The Functions of the Skeletal System
    2. 10.2 Bone Classification
    3. 10.3 Bone Structure
    4. 10.4 Bone Formation and Development
    5. 10.5 Fractures: Bone Repair
    6. 10.6 Exercise, Nutrition, Hormones and Bone Tissue
    7. 10.7 Calcium Homeostasis: Interactions of the Skeletal System and Other Organ Systems
    8. 10.8 Divisions of the Skeletal System
    9. 10.9 The Skull
    10. 10.10 The Vertebral Column
    11. 10.11 The Thoracic Cage
    12. 10.12 Embryonic Development of the Axial Skeleton
  18. Musculoskeletal System
    1. 11.1 The Pectoral Girdle
    2. 11.2 Bones of the Upper Limb
    3. 11.3 The Pelvic Girdle and Pelvis
    4. 11.4 Bones of the Lower Limb
    5. 11.5 Development of the Appendicular Skeleton
    6. 11.6 Classification of Joints
    7. 11.7 Fibrous Joints
    8. 11.8 Cartilaginous Joints
    9. 11.9 Synovial Joints
    10. 11.10 Types of Body Movements
    11. 11.11 Anatomy of Selected Synovial Joints
    12. 11.12 Development of Joints
  19. Digestive System
    1. 12.1 Overview of the Digestive System
    2. 12.2 Digestive System Processes and Regulation
    3. 12.3 The Mouth, Pharynx and Oesophagus
    4. 12.4 The Stomach
    5. 12.5 The Small and Large Intestines
    6. 12.6 Accessory Organs in Digestion: the Liver, Pancreas and Gallbladder
    7. 12.7 Chemical Digestion and Absorption
  20. Nervous System
    1. 13.1 Basic Structure and Function of the Nervous System
    2. 13.2 Nervous Tissue
    3. 13.3 The Function of Nervous Tissue
    4. 13.4 The Action Potential
    5. 13.5 Communication between Neurons
    6. 13.6 The Embyrologic Perspective
    7. 13.7 The Central Nervous System
    8. 13.8 Circulation and the Central Nervous System
    9. 13.9 The Peripheral Nervous System
    10. 13.10 Sensory Perception
    11. 13.11 Central Processing
    12. 13.12 Motor Responses
  21. Endocrine System
    1. 14.1 An Overview of the Endocrine System
    2. 14.2 Hormones
    3. 14.3 The Pituitary Gland and Hypothalamus
    4. 14.4 The Thyroid Gland
    5. 14.5 The Parathyroid Glands
    6. 14.6 The Adrenal Glands
    7. 14.7 The Pineal Gland
    8. 14.8 Gonadal and Placental Hormones
    9. 14.9 The Endocrine Pancreas
    10. 14.10 Organs with Secondary Endocrine Functions
    11. 14.11 Development and Ageing of the Endocrine System
  22. Reproductive System
    1. 15.1 Anatomy and Physiology of the Male Reproductive System
    2. 15.2 Anatomy and Physiology of the Female Reproductive System
    3. 15.3 Development of the Male and Female Reproductive Systems
  23. Pregnancy and Human Development
    1. 16.1 Fertilisation
    2. 16.2 Embryonic Development
    3. 16.3 Foetal Development
  24. Urinary System
    1. 17.1 Physical Characteristics of Urine
    2. 17.2 Gross Anatomy of Urine Transport
    3. 17.3 Gross Anatomy of the Kidney
    4. 17.4 Microscopic Anatomy of the Kidney
    5. 17.5 Physiology of Urine Formation
    6. 17.6 Tubular Reabsorption
    7. 17.7 Regulation of Renal Blood Flow
    8. 17.8 Endocrine Regulation of Kidney Function
    9. 17.9 Regulation of Fluid Volume and Composition
    10. 17.10 The Urinary System and Homeostasis
    11. 17.11 Body Fluids and Fluid Compartments
    12. 17.12 Water Balance
    13. 17.13 Electrolyte Balance
    14. 17.14 Acid-Base Balance
    15. 17.15 Disorders of Acid-Base Balance
  25. Appendix A: Unit Measurements and Calculations
  26. Appendix B: Chemical Abbreviations
  27. Glossary
  28. Bibliography

6.11 Development of Blood Vessels and Foetal Circulation

Learning Objectives

By the end of this section, you will be able to:

  • Describe the development of blood vessels
  • Describe the foetal circulation

In a developing embryo, the heart has developed enough by day 21 post-fertilisation to begin beating. Circulation patterns are clearly established by the fourth week of embryonic life. It is critical to the survival of the developing human that the circulatory system forms early to supply the growing tissue with nutrients and gases, and to remove waste products. Blood cells and vessel production in structures outside the embryo proper called the yolk sac, chorion, and connecting stalk begin about 15 to 16 days following fertilisation. Development of these circulatory elements within the embryo itself begins approximately 2 days later. You will learn more about the formation and function of these early structures when you study the chapter on development. During those first few weeks, blood vessels begin to form from the embryonic mesoderm. The precursor cells are known as haemangioblasts. These in turn differentiate into angioblasts, which give rise to the blood vessels and pluripotent stem cells, which differentiate into the formed elements of blood. (Seek additional content for more detail on foetal development and circulation.) Together, these cells form masses known as blood islands scattered throughout the embryonic disc. Spaces appear on the blood islands that develop into vessel lumens. The endothelial lining of the vessels arise from the angioblasts within these islands. Surrounding mesenchymal cells give rise to the smooth muscle and connective tissue layers of the vessels. While the vessels are developing, the pluripotent stem cells begin to form the blood.

Vascular tubes also develop on the blood islands, and they eventually connect to one another as well as to the developing, tubular heart. Thus, the developmental pattern, rather than beginning from the formation of one central vessel and spreading outward, occurs in many regions simultaneously with vessels later joining together. This angiogenesis—the creation of new blood vessels from existing ones—continues as needed throughout life as we grow and develop.

Blood vessel development often follows the same pattern as nerve development and travels to the same target tissues and organs. This occurs because the many factors directing growth of nerves also stimulate blood vessels to follow a similar pattern. Whether a given vessel develops into an artery or a vein is dependent upon local concentrations of signalling proteins.

As the embryo grows within the mother’s uterus, its requirements for nutrients and gas exchange also grow. The placenta—a circulatory organ unique to pregnancy—develops jointly from the embryo and uterine wall structures to fill this need. Emerging from the placenta is the umbilical vein, which carries oxygen-rich blood from the mother to the foetal inferior vena cava via the ductus venosus to the heart that pumps it into foetal circulation. Two umbilical arteries carry oxygen-depleted foetal blood, including wastes and carbon dioxide, to the placenta. Remnants of the umbilical arteries remain in the adult.

There are three major shunts—alternate paths for blood flow—found in the circulatory system of the foetus. Two of these shunts divert blood from the pulmonary to the systemic circuit, whereas the third connects the umbilical vein to the inferior vena cava. The first two shunts are critical during foetal life, when the lungs are compressed, filled with amniotic fluid, and non-functional, and gas exchange is provided by the placenta. These shunts close shortly after birth, however, when the newborn begins to breathe. The third shunt persists a bit longer but becomes non-functional once the umbilical cord is severed. The three shunts are as follows (Figure 6.11.1).

The foramen ovale is an opening in the interatrial septum that allows blood to flow from the right atrium to the left atrium. A valve associated with this opening prevents backflow of blood during the foetal period. As the newborn begins to breathe and blood pressure in the atria increases, this shunt closes. The fossa ovalis remains in the interatrial septum after birth, marking the location of the former foramen ovale.

The ductus arteriosus is a short, muscular vessel that connects the pulmonary trunk to the aorta. Most of the blood pumped from the right ventricle into the pulmonary trunk is thereby diverted into the aorta. Only enough blood reaches the foetal lungs to maintain the developing lung tissue. When the newborn takes the first breath, pressure within the lungs drops dramatically, and both the lungs and the pulmonary vessels expand. As the amount of oxygen increases, the smooth muscles in the wall of the ductus arteriosus constrict, sealing off the passage. Eventually, the muscular and endothelial components of the ductus arteriosus degenerate, leaving only the connective tissue component of the ligamentum arteriosum.

The ductus venosus is a temporary blood vessel that branches from the umbilical vein, allowing much of the freshly oxygenated blood from the placenta—the organ of gas exchange between the mother and foetus—to bypass the foetal liver and go directly to the foetal heart. The ductus venosus closes slowly during the first weeks of infancy and degenerates to become the ligamentum venosum.

Foetal shunts
Figure 6.11.1. Foetal shunts. The foramen ovale in the interatrial septum allows blood to flow from the right atrium to the left atrium. The ductus arteriosus is a temporary vessel, connecting the aorta to the pulmonary trunk. The ductus venosus links the umbilical vein to the inferior vena cava largely through the liver.

Section Review

Blood vessels begin to form from the embryonic mesoderm. The precursor haemangioblasts differentiate into angioblasts, which give rise to the blood vessels and pluripotent stem cells that differentiate into the formed elements of the blood. Together, these cells form blood islands scattered throughout the embryo. Extensions known as vascular tubes eventually connect the vascular network. As the embryo grows within the mother’s womb, the placenta develops to supply blood rich in oxygen and nutrients via the umbilical vein and to remove wastes in oxygen-depleted blood via the umbilical arteries. Three major shunts found in the foetus are the foramen ovale and ductus arteriosus, which divert blood from the pulmonary to the systemic circuit, and the ductus venosus, which carries freshly oxygenated blood high in nutrients to the foetal heart.

Review Questions

An interactive H5P element has been excluded from this version of the text. You can view it online here:
https://usq.pressbooks.pub/anatomy/?p=526#h5p-147

Critical Thinking Questions

An interactive H5P element has been excluded from this version of the text. You can view it online here:
https://usq.pressbooks.pub/anatomy/?p=526#h5p-148

An interactive H5P element has been excluded from this version of the text. You can view it online here:
https://usq.pressbooks.pub/anatomy/?p=526#h5p-149

Click the drop down below to review the terms learned from this chapter.

An interactive H5P element has been excluded from this version of the text. You can view it online here:
https://usq.pressbooks.pub/anatomy/?p=526#h5p-150

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