REVISED BIO 245 Exam 2 Prep

What is the lymphatic system composed of

Lymph vessels and lymphoid structures

What is lymph

Interstitial fluid that has entered lymphatic capillaries

How is interstitial fluid moved into lymphatic capillaries

Hydrostatic pressure drives fluid through intercellular openings (flaps) between endothelial cells

What happens to endothelial flaps when lymphatic capillary fills

Increased pressure closes flaps preventing backflow

Components of lymph

Water, dissolved solutes (ions), small proteins, cellular debris, pathogens, cancer cells

What is the direction of lymph flow

One-way toward the heart

Does the lymphatic system have a pump

No, it relies on external forces

Mechanisms that move lymph

Skeletal muscle pump, respiratory pump, arterial pulsation, rhythmic smooth muscle contraction

Structure of lymphatic vessels

Three tunics (intima, media, externa) and valves to prevent backflow

Relationship between lymphatic vessels and blood vessels

Located adjacent to arteries and veins

What is the function of lymphatic system in cardiovascular support

Returns excess interstitial fluid to venous circulation to maintain blood volume and pressure

What are primary lymphoid structures

Sites of lymphocyte production and development

Primary lymphoid structures

Red bone marrow and thymus

Where do all lymphocytes develop

Red bone marrow

Where do B lymphocytes mature

Red bone marrow

Where do T lymphocytes mature

Thymus

What are secondary lymphoid structures

Sites where immune responses are initiated and mature lymphocytes reside

Examples of secondary lymphoid structures

Lymph nodes, spleen, tonsils, MALT

Function of lymph nodes

Filter lymph, remove debris, activate immune cells

Afferent vs efferent lymphatic vessels

Afferent vessels carry lymph into node; efferent vessels carry lymph out

Why lymph flow slows in lymph nodes

Allows time for cleansing and immune activation

Cells involved in lymph node function

Lymphocytes, macrophages, dendritic cells

Structure of lymph node cortex

Contains lymphatic nodules with germinal centers and mantle zones

Structure of lymph node medulla

Contains medullary sinuses and medullary cords leading to hilum

What causes swollen lymph nodes

Proliferation of lymphocytes during immune response

Major lymphatic trunks and regions drained

Jugular (head/neck), subclavian (upper limbs), bronchomediastinal (thorax), lumbar (lower body), intestinal (abdomen)

Which trunk is unpaired

Intestinal trunk

Where do lymphatic trunks drain

Into lymphatic ducts

Right lymphatic duct drains

Right side of head, neck, thorax, and right arm

Thoracic duct drains

Rest of the body

What is cisterna chyli

Enlarged region of thoracic duct collecting lipid-rich lymph from GI tract

Where lymph is returned to circulation

Junction of subclavian and internal jugular veins

Compare pulmonary circulation

Right heart to lungs and back to left heart for gas exchange

Compare systemic circulation

Left heart to body tissues and back to right heart

Compare coronary circulation

Blood supply to heart muscle via coronary arteries and veins

What causes myocardial infarction

Loss of blood flow due to coronary artery blockage (thrombosis)

Structure of pericardium

Fibrous pericardium + serous pericardium (parietal and visceral layers)

Function of fibrous pericardium

Mechanical protection and anchoring heart

Function of serous pericardium

Reduces friction via serous fluid

What is pericarditis

Inflammation causing fluid accumulation and impaired heart filling

Pulmonary trunk carries

Deoxygenated blood from right ventricle to lungs

Aorta carries

Oxygenated blood from left ventricle to body

Pulmonary veins carry

Oxygenated blood to left atrium

Vena cavae carry

Deoxygenated blood to right atrium

Right atrium receives blood from

SVC, IVC, coronary sinus

Left atrium receives blood from

Pulmonary veins

Right ventricle pumps blood to

Pulmonary trunk

Left ventricle pumps blood to

Aorta

Which chamber has thickest wall

Left ventricle

What are pectinate muscles

Ridges in atria walls

What are papillary muscles

Anchor chordae tendineae in ventricles

Function of chordae tendineae

Prevent AV valve prolapse

AV valves location

Between atria and ventricles

Semilunar valves location

Between ventricles and arteries

Function of cardiac skeleton

Structural support, valve attachment, electrical insulation

Layers of heart wall

Epicardium, myocardium, endocardium

What are intercalated discs

Cell junctions connecting cardiac muscle cells

Function of gap junctions

Allow electrical signals to pass between cells

Function of desmosomes

Prevent cells from pulling apart

SA node function

Initiates action potential (pacemaker)

AV node function

Delays signal before passing to ventricles

Purkinje fibers function

Distribute action potential through ventricles

What is pacemaker potential

Gradual depolarization due to Na+ influx

Threshold of nodal cells

Approximately -40 mV

Depolarization in nodal cells

Ca2+ influx

Repolarization in nodal cells

K+ efflux

Depolarization in cardiac muscle cells

Fast Na+ influx

Plateau phase

Ca2+ influx balances K+ efflux

Repolarization

K+ efflux

Why plateau phase is important

Prevents tetany and allows sustained contraction

Role of T-tubules

Carry action potentials into cell interior

Role of sarcoplasmic reticulum

Releases Ca2+ for contraction

Five phases of cardiac cycle

Atrial systole, isovolumetric contraction, ventricular ejection, isovolumetric relaxation, ventricular filling

What is EDV

End diastolic volume (max filling)

What is ESV

End systolic volume (remaining blood)

Stroke volume equation

SV (stroke volume) = EDV (end-diastolic volume) - ESV (end-systolic volume)

Cardiac output equation

CO = HR × SV

What is heart rate

Beats per minute

What is stroke volume

Blood ejected per beat

Positive chronotropic agents

Increase heart rate (sympathetic stimulation, EPI/NE)

Negative chronotropic agents

Decrease heart rate (parasympathetic, beta-blockers)

Three factors affecting stroke volume

Venous return, afterload, contractility

What is venous return

Blood returning to heart

Effect of increased venous return

Increases EDV and stroke volume

What is afterload

Resistance to ejection of blood

Effect of increased afterload

Decreases stroke volume

Positive inotropic agents

Increase contractility via increased Ca2+

Negative inotropic agents

Decrease contractility via reduced Ca2+

Compare arteries

High pressure, thick walls, large tunica media, carry blood away from heart

Compare veins

Low pressure, valves, large lumen, act as blood reservoir

Compare capillaries

Smallest vessels, thin walls, site of exchange

Three types of capillaries

Continuous, fenestrated, sinusoid

Continuous capillaries

Least permeable, found in skin, muscles, CNS

Fenestrated capillaries

Moderately permeable, found in kidneys and endocrine organs

Sinusoid capillaries

Most permeable, found in liver, spleen, bone marrow

Structure of capillary bed

Metarteriole, true capillaries, thoroughfare channel, venule

What controls blood flow in capillary beds

Precapillary sphincters

What is vasomotion

Cyclic contraction/relaxation of sphincters

What percentage of capillaries open at once

About 25%

Simple pathway

Artery → capillary → vein