1. Fetal Circulation UNIT B lungs are not functional in the fetus.
Chapter 10: Circulatory System and Lymphatic System
Section 10.5
Fetal Circulation
lungs are not functional in the fetus.
Blood passes directly from the right atrium to the left atrium through the foramen ovale between the atria.
Any blood that does not enter the right ventricle and is pumped into the pulmonary trunk is shunted into the aorta by the ductus arteriosus.
Umbilical arteries take fetal blood to the placenta, where the exchange of gases and nutrients between maternal blood and fetal blood takes place.
The umbilical vein then carries the nutrient and O2-rich blood to the fetus.
foramen ovale: the flap dividing the left atrium from the right atrium of the heart
ductus arteriosus: provides a pathway for returning any blood that enters the right ventricle back to the aorta, bypassing lungs
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2. 5. Ductus Venosus (venous duct) – an extra vessel which connects the umbilical vein to the posterior vena cava, bypassing fetal liver

3. UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.5
Figure Fetal circulation. The lungs are not functional in the fetus, and the blood passes directly from the right atrium to the left atrium or from the right ventricle to the aorta. The umbilical arteries take fetal blood to the placenta, and the umbilical vein returns fetal blood from the placenta.
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4. Structure and Function of the Placenta
UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.5
Structure and Function of the Placenta
The placenta is attached to the uterine wall by the allantois and chorionic villi.
Functions only before birth; becomes part of the afterbirth when child is born
Involved in gas, nutrient, and waste exchange between the fetal and maternal circulatory systems
Umbilical cord contains the umbilical arteries and vein, which transport waste to the placenta, and take oxygen and nutrients to the fetal circulatory system
placenta: an organ that functions in gas, nutrient, and waste exchange between the embryonic (later fetal) and maternal circulatory systems
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5. UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.5
Figure The Placenta. At the placenta, an exchange of molecules between fetal and maternal blood takes place across the walls of the chorionic villi. Oxygen and nutrient molecules diffuse into the fetal blood, and carbon dioxide and urea diffuse out of the fetal blood.
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6. The Lymphatic System UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.6
The Lymphatic System
The lymphatic system consists of lymphatic vessels and the lymphoid organs. It is closely associated with the circulatory system.
The lymphatic system has three main functions:
Lymphatic capillaries absorb excess tissue fluid and return it to the bloodstream
Lymphatic capillaries absorb fats from the digestive tract and transport them to the bloodstream
Lymphoid organs defend the body against disease
lymphatic system: a type of organ system consisting of lymphatic vessels, lymph nodes, and other lymphatic organs; transports lymphs and lipids, and aids the immune system
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7. UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.6
Figure Lymphatic system. Lymphatic vessels drain excess fluid from the tissues and return it to the circulatory system. Lymphatic vessels, like circulatory veins, have valves to prevent backward flow.
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8. Lymphatic Vessels UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.6
Lymphatic Vessels
Lymphatic vessels form a one-way system that begins with the lymphatic capillaries.
Lymphatic capillaries (tiny, closed-ended vessels) absorb excess tissue fluid called lymph.
Tissue fluid contains water, solutes (nutrients, electrolytes, oxygen), and cellular products (hormones, enzymes, wastes)
lymphatic vessels: a one-way system that carries lymph
lymphatic capillaries: collect excess tissue fluid called lymph
lymph: tissue fluid contained within lymphatic vessels
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9. Compare Lymphatic Capillaries to Blood Capillaries
have valves,
are slightly larger in diameter,
have closed ends (unlike the loop structure of blood capillaries).
Unique structure permits interstitial fluid to flow in but not out.
The ends of the endothelial cells that make up the wall of a lymphatic capillary overlap.
Both have valves

10. Movement of Lymph in Lymphatic Vessels
UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.6
Movement of Lymph in Lymphatic Vessels
The lymphatic capillaries join to form lymphatic vessels that merge before entering one of two ducts:
Thoracic duct: returns lymph collected from the left side of the body into the left subclavian vein
Right lymphatic duct: returns lymph collected from the right side of the body into the right subclavian vein
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11. Movement of Lymph in Lymphatic Vessels
UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.6
Movement of Lymph in Lymphatic Vessels
Movement of lymph in the lymphatic capillaries is dependent on skeletal muscle contraction
One-way valves in the vessels prevent lymph from flowing backward
Lymph percolates through various lymph nodes, where foreign material can be recognized by the immune system
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12. UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.6
Edema
Edema is localized swelling caused by the accumulation of tissue fluid that has not been collected by the lymphatic system.
Occurs if too much tissue fluid is made and/or if not enough is drained away
Can lead to tissue damage and death
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13. UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.6
Lymphoid Organs
Lymphoid organs contain large numbers of lymphocytes (white blood cells involved in adaptive immunity).
There are two types of lymphoid organs:
Primary lymphoid organs: red bone marrow and thymus, where lymphocytes develop and mature
Secondary lymphoid organs: lymph nodes and spleen, where lymphocytes become activated
lymphoid organs: organs that contain large number of lymphocytes; can be primary or secondary lymphoid organs
lymphocytes: have two major types: B lymphocytes produce antibodies, T lymphocytes can either regulate the responses of other cells or can kill other cells
primary lymphoid organs: organs where lymphocytes develop and mature; includes red bone marrow and thymus
secondary lymphoid organs: organs in which some lymphocytes become activated; includes lymph nodes and spleen
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14. UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.6
Figure The lymphoid organs. The thymus (a) and red bone marrow (b) are the primary lymphoid organs. Blood cells, including lymphocytes, are produced in red bone marrow. B cells mature in the bone marrow. T cells mature in the thymus. The lymph nodes (c) and the spleen (d) are secondary lymphoid organs. Lymph is cleansed in the nodes, and blood is cleansed in the spleen.
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15. Primary Lymphoid Organs
UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.6
Primary Lymphoid Organs
Red bone marrow
Contains a network of connective
tissue fibres, along with stem cells
that can divide and produce blood cells
Lymphocytes begin development in the
bone marrow
B lymphocytes (B cells) begin in bone marrow and then migrate to secondary lymphoid organs to mature
T lymphocytes (T cells) in bone marrow and then migrate to the thymus, where they mature and differentiate
red bone marrow: a primary lymphoid organ where lymphocytes begin their development; contains a network of connective tissue fibres, along with stem cells that are able to divide and produce blood cells
B cells: lymphocytes that remain in bone marrow until mature; also called B lymphocytes
T cells: lymphocytes that migrate from bone marrow to the thymus where they mature and differentiate
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16. Primary Lymphoid Organs
UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.6
Primary Lymphoid Organs
Thymus
lobules, filled with T cells and supporting cells
Lobules are lined with epithelial cells that secrete hormones called thymosins, which are involved in the differentiation of T cells
T cells that react to the body’s own cells undergo apoptosis (programmed cell death)
T cells that leave the thymus can react to foreign molecules
thymus: a primary lymphoid organ that secretes the hormone thymosins, which aids in the differentiation of T cells
Thymus
Connective tissue divides the thymus into lobules, which are filled with T cells and supporting cells
Lobules are lined with epithelial cells that secrete hormones called thymosins, which are involved in the differentiation of T cells
T cells that react to the body’s own cells undergo apoptosis (programmed cell death)
T cells that leave the thymus can react to foreign molecules
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17. Secondary Lymphoid Organs
UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.6
Secondary Lymphoid Organs
Spleen
Cleanses blood
Thin capsule surrounding white (filters debris and bacteria) and red pulp ( macrophages filter worn out RBC)
May be surgically removed due to trauma or disease, however the body becomes more susceptible to certain types of infections
spleen: a secondary lymphoid organ that removes old and defective blood cells, as well as reacts to foreign invaders
Thin capsule can burst from injury. Surgical removal may lead to susceptibility to infections
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18. Secondary Lymphoid Organs
UNIT B
Chapter 10: Circulatory System and Lymphatic System
Section 10.6
Secondary Lymphoid Organs
Lymph nodes
Cleanse lymph
Occur along lymphatic vessels
Connective tissue divides nodes into nodules, each of which contain B cells, T cells, and a sinus
As lymph passes through the sinuses, macrophages engulf pathogens.
Cancer cells can enter the lymph nodes and lymphatic vessels and move through to other regions of the body, where they produce secondary tumours (metastasis)
lymph nodes: masses of lymphatic tissue located along the course of a lymphatic vessel
pathogens: disease-causing agents such as viruses and bacteria
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