lesson 4 midterm ( circulatory system) Flashcards
Circulates blood throughout the body.
- Components: Arteries, veins, capillaries, and the heart.
Blood Vascular System
- Key Feature: Driven by the heart, a muscular pump that keeps blood flowing in a closed loop.
*Purpose: Delivers oxygen and nutrients to tissues; removes carbon dioxide and waste.
Blood Vascular System
`*Function: Returns excess fluid from tissues back to the bloodstream.
*Components: Lymphatic vessels, lymph, lymph nodes.
Lymph Vascular System
- Key Feature: Collects lymph (fluid that leaks out of blood capillaries).
- Purpose: Maintains fluid balance and filters pathogens via lymph nodes for immune defense.
Lymph Vascular System
4 components of Blood Vascular System
- Heart
- Arteries
- Capillaries
- Veins
Also called: Endothelium, Provides a smooth surface for blood flow and regulates vessel tone and permeability.
Tunica Intima (Inner Layer)
- Lined by a single layer of endothelial cells.
- Supported by a subendothelial layer of loose connective
Tunica Intima (Inner Layer)
May contain occasional smooth muscle cells.
Tunica Intima (Inner Layer)
*Primarily made up of smooth muscle cells.
*Arranged in helical (spiral) layers.
Tunica Media (Middle Layer)
- Controls vasoconstriction and vasodilation (changes in vessel diameter).
- Maintains blood pressure and blood flow.
Tunica Media (Middle Layer)
*Composed mainly of type I collagen and elastic fibers.
*May contain small blood vessels (vasa vasorum) that supply the vessel wall itself.
Tunica Adventitia (or Externa) (Outer Layer)
- Provides structural support and protection.
- Anchors the vessel to surrounding tissues.
Tunica Adventitia (or Externa) (Outer Layer)
Cone-shaped: apex (pointed, bottom part), base (broad, top part).
heart
THE HEART:
Anterior surface: Just behind the sternum and ribs.
Inferior surface: Rests mostly on the diaphragm.
Right surface: Faces the right lung.
Left surface: Faces the left lung and extends to the apex (the pointed tip of the heart pointing downward and leftward).
THE HEART:
Anterior surface: Just behind the sternum and ribs.
Inferior surface: Rests mostly on the diaphragm.
Right surface: Faces the right lung.
Left surface: Faces the left lung and extends to the apex (the pointed tip of the heart pointing downward and leftward).
surrounds and protects the heart, anchoring it securely within the mediastinum.
pericardium
Two Main Parts of the Pericardium:
- Fibrous Pericardium (Outer Layer):
- Serous Pericardium (Inner Double Layer):
Tough, inelastic dense irregular connective tissue. Prevents overstretching of the heart. Protects and anchors the heart.
Fibrous Pericardium (Outer Layer):
Thin, delicate membrane.
Serous Pericardium
Serous Pericardium Forms two layers:
Parietal Layer
Visceral Layer (Epicardium) –
fused to the fibrous pericardium.
Parietal Layer
directly on the heart’s surface (also part of heart wall).
Visceral Layer (Epicardium)
Layers of the Heart:
Epicardium
Myocardium
Endocardium
Outer layer of the heart
Made of mesothelium and fatty connective tissue
Epicardium
Provides a smooth protective surface
Also called visceral layer of the serous pericardium
Epicardium
Middle and thickest layer
Made of cardiac muscle tissue
Myocardium
Makes up 95% of heart wall
Muscle fibers are striated and involuntary
Myocardium
Responsible for pumping action
Myocardium
Innermost layer
Composed of endothelium and connective tissue
Endocardium
Lines heart chambers and valves
Smooth surface reduces blood flow friction
Endocardium
Continuous with blood vessel lining
Endocardium
The heart has 4 chambers:
- atria (receive blood)
- ventricles (pump blood)
Forms the right surface of the heart
*
Right Atrium
Right Atrium Receives blood from:
➢Superior vena cava
➢Inferior vena cava
➢Coronary sinus
Increase force of contraction without
thickening the w
Pectinate muscles (in anterior wall &
auricle):
Remnant of fetal foramen ovale
Fossa ovalis:
Forms most of the anterior surface of the heart
*
Right Ventricle
Prevent walls
from sticking during contraction; Aid in conduction
system
Trabeculae carneae (muscle ridges)
Prevent valve cusps from
inverting
Chordae tendineae:
Anchor chordae tendineae;
Contract to keep valves closed during systole
Papillary muscles:
Pumps blood through ____ into _____ → lungs
pulmonary valve, pulmonary
trunk
Forms most of the base of the heart
*
Left Atrium
Left Atrium Receives oxygenated blood from:
4 pulmonary veins
Contains pectinate muscles
Auricle
Promotes efficient blood
flow
Smooth inner wall:
Thickest heart chamber
Forms the apex of the heart
Left Ventricle
Prevent suction between walls;
Support powerful contraction
Trabeculae carneae:
: Same function
as in right ventricle
Chordae tendineae & papillary muscles:
Pumps blood through aortic valve → aorta → whole
body
Left Ventricle
as the name
suggests located between atria and
ventricles
Atrioventricular (AV) Valves
- 3 cusps (leaflets)
- Between right atrium & right
ventricle
❑Right AV valve → Tricuspid Valve
- 2 cusps
- Between left atrium & left ventricle
Left AV valve → Bicuspid (Mitral) Valve
Located between
ventricles and major arteries
Semilunar Valves
Between right ventricle & pulmonary trunk
Pulmonary Valve
Between left ventricle & aorta
Aortic Valve
Pathway:
Heart → Lungs → Heart
oxygen level: Carries deoxygenated blood to lungs, returns oxygenated blood to heart
Pulmonary Circulation
Pathway:Heart → Body (tissues/organs) → Heart
Oxygen Level: Carries oxygenated blood to body; returns deoxygenated blood to heart
Systemic Circulation
Deliver oxygenated blood to the myocardium (heart muscle).
Coronary Arteries:
Branches into anterior interventricular artery and circumflex artery. Supplies left side of the heart.
Left Coronary Artery
Supplies right atrium and most of the right ventricle. Branches into marginal and posterior interventricular arteries
Right Coronary Artery
Drain deoxygenated blood from the myocardium.
Coronary Veins
Collects blood from cardiac veins and empties into the right atrium.
Coronary Sinus:
Delays impulse to allow atria to fully contract before ventricles.
Atrioventricular (AV) Node
Acts as the natural pacemaker; initiates electrical impulses.
Sinoatrial (SA) Node
Stimulate ventricular muscle contraction, enabling powerful pumping
Purkinje Fibers
Conduct impulses through the septum to the apex of the heart.
Right & Left Bundle Branches
Transmits impulses from AV node to the ventricles.
AV Bundle (Bundle of His)
Carries oxygenated blood from the heart to all parts of the body.
walls are thick, muscular, and elastic to withstand high pressure and help regulate blood flow.
Arterial System:
Refers to the smallest and most delicate blood vessels in the body, which are essential for exchanging gases,
Microcirculation / Microvasculature
Responsible for returning deoxygenated blood back to the heart.
Venous System
acts as a blood reservoir, containing the majority of the body’s blood volume
Venous System
Largest arteries
dominated by elastic fibers
act as pressure reservoirs
Elastic Arteries
also known as distributing arteries
allows vasoconstriction and vasodilation
dominated by smooth muscle
Muscular Arteries
Also called resistance vessels because they regulate blood pressure and control blood flow into capillary beds.
Contain precapillary sphincters and Regulate resistance
Arterioles/ resistance vessels
Distribute blood to organs
Muscular Arteries
Arises from the left ventricle
Ascending Aorta
supplies right atrium, right ventricle, part of left ventricle, and conduction system
Right coronary artery
branches into:
*
Anterior interventricular (LAD) artery
*
Circumflex artery
Left coronary artery
Extend laterally to become axillary arteries
Subclavian Arteries
ascends to brain via transverse foramina of cervical vertebrae
Vertebral artery
anterior chest wall
Internal thoracic artery
thyroid gland, neck muscles
Thyrocervical trunk
deep neck and upper intercostal spaces
Costocervical trunk
the level of C3–C4 into:
❑
Internal carotid artery → brain
❑
External carotid artery → face, scalp, jaw
Continues from the aortic arch
Descending Aorta
Abdominal aorta (starts at T12 after passing through diaphragm)
gives off:
*Celiac trunk → liver, stomach, spleen
* Superior mesenteric artery → small intestine, part of large intestine
* Renal arteries → kidneys
* Gonadal arteries → testes or ovaries
* Inferior mesenteric artery → distal colon
Occurs around L4 vertebral level
Terminal Branches of the Abdominal Aorta
continues as femoral artery into lower limb
External iliac artery
are the primary vessels in microcirculation—extremely thin-walled and interconnected to form networks where this exchange occurs.
Capillaries
most common; uninterrupted lining, found in muscle, skin, lungs, and the CNS.
Continuous Capillaries
have pores (fenestrations) for increased permeability; found in kidneys, endocrine glands, and intestines
Fenestrated Capillaries
large gaps in the endothelium and basement membrane; found in liver, spleen, and bone marrow.
Discontinuous (Sinusoidal) Capillaries
collect blood from capillaries and unite to form larger veins.
Venules
They operate under low pressure, have thin walls, and can store large volumes of blood, acting as a reservoir.
Veins
are present, especially in the limbs, to prevent backflow and assist blood flow toward the heart.
Valves
Smooth lining; forms valves to prevent backflow
Tunica Intima
Middle layer of smooth muscle
Tunica Media
Outer layer of collagen and elastic fibers
Tunica Externa
Folds of tunica intima
Valves
- Mostly water (90%)
- Contains proteins (albumin, globulin, fibrinogen), electrolytes, nutrients, hormones, and waste products.
Plasma (55%)
- Red Blood Cells (RBCs) – transport oxygen.
- White Blood Cells (WBCs) – immune defense.
*Platelets (Thrombocytes) – clot formation.
Formed Elements (45%)
- Red Blood Cells (RBCs) – transport oxygen.
- White Blood Cells (WBCs) – immune defense.
*Platelets (Thrombocytes) – clot formation.
Filled with hemoglobin to carry oxygen and carbon dioxide.
Red Blood Cells (RBCs)
- Function: Transport oxygen from lungs to tissues and return CO₂ to lungs.
- Lifespan: ~120 days.
Red Blood Cells (RBCs)
- Based on presence/absence of A and B antigens on RBCs.
*Types: A, B, AB, and O.
ABO System
- Based on Rh factor (D antigen).
- Rh⁺ (positive): antigen present.
- Rh⁻ (negative): antigen absent.
Rh System:
First responders, phagocytosis of bacteria
Neutrophils
Combat parasites, modulateallergicresponse
Eosinophils
Release histamine and heparin,
Basophils
Cell fragments from megakaryocytes
Platelets
adhere to damaged vessel walls, aggregate, and form plugs.
hemostasis
is a network of threadlike protein fibers,
blood clot
, that traps blood cells, platelets, and fluid.
fibrin
The formation of a blood clot depends on a number of proteins, called _____found within plasma.
clotting factors, or coagulation factors,
Clear fluid derived from interstitial fluid; contains lymphocytes, waste products, and sometimes pathogens.
Lymph
Small, thin-walled vessels in tissues that absorb interstitial fluid.
Lymphatic Capillaries
Larger vessels with valves that transport lymph toward the heart.
Lymphatic Vessels
Small, bean-shaped organs along lymph vessels; filter lymph and house immune cells.
Lymph Nodes
Larger collecting vessels that drain regions of the body.
Lymphatic Trunks
Drains most of the body into the left subclavian vein
Thoracic Duct
Drains right upper quadrant into the right subclavian vein.
Right Lymphatic Duct
Include tonsils, spleen, thymus, and Peyer’s patches
Lymphoid Organs
Site of hematopoiesis (formation of blood cells). Produces all lymphocytes; B cells mature here.
Bone Marrow
Site where T lymphocytes (T cells) mature
Thymus
Filter lymph and trap foreign substances. Sites of immune cell activation
Lymph Nodes
Filters blood, removes old RBCs, stores platelets, and initiates immune responses.
Spleen
Protect against inhaled or ingested pathogens
Tonsils
Monitor intestinal bacteria and prevent growth of pathogenic microbes.
Peyer’s Patches
Prevents tissue swelling (edema).
Drain Excess Interstitial Fluid –
Lacteals (specialized lymphatic capillaries in the intestine) absorb fats and transport them to the bloodstream.
Transport Dietary Fats
Lymph nodes and other lymphoid organs detect and respond to pathogens
Immune Surveillance and Response
Recovers proteins that escape blood capillaries.
Return Proteins to Bloodstream
Outer layer containing lymphoid follicles with germinal centers
Cortex
Deep to cortex, rich in T cells
Paracortex
Inner region with medullary cords and sinuses
Medulla
Vessels that bring lymph into the lymph node
Vessels that carry lymph out of the node (exit at hilum)
Afferent lymphatic vessels
Efferent lymphatic vessels
Largest lymphoid organ;
Spleen
___- (lymphatic tissue) and ____ (blood-filled sinuses).
white pulp , red pulp
*
Filters blood, not lymph.
*
Removes old or damaged red blood cells.
*
Stores platelets and acts as a blood reservoir.
*
Initiates immune responses to blood-borne antigens.
Spleen
Bi-lobed organ in the mediastinum, behind the sternum. Prominent in children, shrinks after puberty.
Thymus
Site of T lymphocyte maturation.
Thymus
last part of the small intestine)
ileum
Initiate immune responses to antigens in the gut, contributing to gut-associated lymphoid tissue (GALT).
Peyer’s Patches
is a network of thin-walled, endothelial-lined vessels that help maintain fluid balance in the body
lymphatic vascular system
It collects excess interstitial fluid (now called lymph) from tissue spaces
Lymphatic Vascular System
*Structure: Begin as small, closed-ended tubes in tissue spaces.
Lymphatic Capillaries
*
Function: Absorb excess fluid, proteins, and waste products from the interstitial space.
*
Lymphatic Capillaries
*
Special Features: More permeable than blood capillaries, allowing uptake of larger molecules like lipids and immune cells.
Lymphatic Vascular System
empties into the left subclavian vein
Entire left side of bo
Thoracic duct
Drains into the right subclavian vein
Right lymphatic duct
