Topic 14: Circulatory System

circulatory system

consists of a heart, vessels, and fluid (blood) that move cells and important molecules (i.e oxygen, nutrients hormones, CO2, and other wastes) from 1 tissue another ly

both macrophages and dendrites have….

have an MCH class 2

lymphatic system

an accessory system of vessels and organs that helps balance the fluid content of the blood and surrounding tissues and participates in the body’s defenses against invading disease organisms

How do very small or very thin animals move molecules?

simple diffusion 

How to larger animals move molecules?

use circulatory systems to bring fluids close to cells so that gases and nutrients can be exchanged

Do sponges, cnidarians, and flatworms use a circulatory system?

no, they use simple diffusion

What do cnidarians have that moves molecules?

a central gastrovascular cavity with a mouth through which water enters and leaves

fluid

a specialized medium that carries cells, oxygen, nutrients, CO2, and wastes, and plays a major role in homeostasis

heart

the muscle that pumps fluid through the circulatory system

vessels

tubular vessels distribute the fluid pumped by the heart

open circulatory system 

vessels leaving the heart release bloodlike fluid (hemolymph) directly into body spaces (sinuses) that surrounds organs, the hemolymph reenters the heart through valves in the heart wall 

close circulatory system

the fluid (blood) is confined to blood vessels and is distinct from the interstitial fluid, substances are exchanges between blood and interstitial fluid, and then between interstitial fluid and cells 

What type of circulatory system do arthropods and mollusks have? why”

open circulatory system with one or more muscular hearts because these animals are sedentary, or their tissues don’t need a lot of oxygen and nutrients

What type of circulatory system does annelids, cephalopod mollusks, and all vertebrates have?

close circulatory systems

• arteries conduct blood away from the heart (at high pressure) 

• nutrients and wastes are exchanges between the blood and body tissues by diffusion across the thin walls of capillaries 

• blood returns to the heart through veins (at low pressure) 

atria

receive blood returning to the heart

ventricles

pump blood from the heart

How many atria and ventricles are do sharks and bony fishes have?

one atrium and one ventricle

• the ventricle pumps blood → the capillaries of the gills where blood releases CO2 and picks up O2

• oxygenated blood is delivered to capillary networks in other body tissues, where it delivers CO2 and drops off CO2

• deoxygenated blood returns to the atrium in veins

How many atria and ventricles do amphibians have?

two atria and one ventricle

• oxygenated blood from the lungs and skin enters the left atrium

• deoxygenated blood from the body enters the right atrium

• the ventricle pumps mostly oxygenated blood into a systemic circuit, which supplies most tissues of the body

• mostly deoxygenated blood is pumped to pulmocutaneous circuit, which leads to the lungs and skin

How many atria and ventricles to turtles, lizards, and snakes have?

2 atria and 1 ventricle

• a flap of tissue in the ventricle (incomplete or deviated septum) keeps oxygenated and deoxygenated blood almost completely separate 

• the systemic circuit carries oxygenated blood to body tissues 

• the pulmonary circuit carries deoxygenated blood to the lungs 

How many atria and ventricles do crocodilians, birds, and mammals have?

two atria and two ventricles (double heart)

• each ½ of the heart operates as a separate pump, restricting the blood circulation to completely separate pulmonary and systemic circuits 

• blood is pumped by a ventricle in each circuit, so both operate at a relatively high pressure 

What is human blood made of?

cells (erythrocytes, leukocytes, and platelets) suspended in a clear liquid matrix called plasma 

What do blood transport cells and molecules do?

stabilize pH and salt composition of body fluids, regulate body temperature by transferring heat

How much blood does the average human has? What are the percentages of its components?

4-5 L

• liquid plasma makes up 55-58% 

• the remaining solid (cellular) components make up the hematocrit 

In humans, where do blood cells develop?

in red bone marrow, primarily in vertebrae, sternum, ribs, and pelvis

Where do blood cells originate from?

from pluripotent stem cells, which retain the embryonic capacity to divide

What are the that cell types that pluripotent stem cells differentiate into?

• myeloid progenitors (stem cells)

• lymphoid progenitors (stem cells)

myeloid progenitors (stem cells)

gives rise to erythrocytes, platelets, neutrophils, basophils, eosinophils, and monocytes

lymphoid progenitor (stem cells)

give rise to B lymphocytes and T lymphocytes, which function in the immune system

What are the components of blood plasma?

• water (91%-92%) 

• glucose and other sugars 

• amino acids 

• plasma proteins 

• dissolved gasses (mostly O2, CO2, and N)

• ions 

• lipids 

• vitamins 

• hormones and other signal molecules

• metabolic wastes (urea and uric acid) 

plasma proteins include:

• albumin

• globulins

• fibrinogen

albumin

• important for osmotic balance and pH buffering

• also transport hormones, therapeutic drugs, and metabolic wastes through the circulatory system

globulins

transports lipids and fat-soluble vitamins

• the immunoglobulins- constitute antibodies and other immune system molecules

• some are also enzymes

fibrinogen 

essential in blood clotting 

Where are most plasma proteins synthesized?

the liver, immunoglobins are synthesized by B and T lymphocytes 

What ions are in plasma?

Na+, Cl- (the 2 most abundant), Ca 2+, HCO3- (bicarbonate)

erythrocytes 

red blood cells, disc-like cells containing large quantities of the oxygen carrying protein Hb

What do mammalian erythrocytes lose? What effect does this have?

nucleus, cytoplasmic organelles. and ribosomes which limits life span

How many erythrocytes are produced om the average human per second?

2-3 million

What is the life span of an erythrocyte?

120 days, after which they are engulfed and destroyed by macrophages in the spleen, liver, and bone marrow

What type of mechanism controls the number of erythrocytes?

negative feedback mechanisms

What happens if there is a low oxygen content in the body?

the kidneys will release erythropoietin (EPO) which stimulates bone marrow stem cells to increase erythrocyte production 

What are human blood groups determined by?

by antigens on the surfaces of erythrocytes

amenia

a disorder of erythrocytes where there are too few or malfunctioning erythrocytes, preventing oxygen from reaching body tissues in sufficient amounts 

leukocytes

white blood cells, eliminate dead or dying cells from the body, remove cellular debris and defend against invading organisms, some have specific function within the immune system 

What do leukocytes retain as they mature and are fully functioning?

nucleus, cytoplasmic organelles, and ribosomes

platelets

• (thrombocytes or fragments of megakaryocytes) small vesicles that contain enzymes and other factors that take part in blood clotting

• aggregating the releases cytokines, which attract more

What happens when blood vessels are damaged?

• platelets in the leaking blood stick to collagen fibers and release signaling molecules that induce additional platelets to stick to them, forming a plug 

• platelets release other factors that convert soluble fibrinogen into insoluble fibrin 

fibrin

forms a mesh like network that traps blood cells and platelets, forming a blood clot

atrioventricular valves (AV)

between the atria and ventricles, keeps blood from moving backward 

semilunar (SL) valves

between the ventricles and arteries leaving the heart, keep blood from moving backwards

pulmonary circuit 

brings deoxygenated blood to the lungs to get oxygenated, then blood is returned to the heart (right side of the heart)

systemic circuit 

delivers oxygenated blood to the body tissues, then the deoxygenated blood is returned to the heart (left side of the heart)

coronary circulation 

oxygenated blood leaving the heart (through the aorta) and supplying the cardiac muscle cells, empties back into the right atrium and the pulmonary circuit 

septum

separation of oxygenated and deoxygenated blood, leads to the capability of double circulation

What does each heartbeat represent?

one cardiac cycle

systole

ventricular contraction and emptying (high pressure)

diastole

relaxation, filling between contractions (low pressure)

What do the first and second sounds of the “lub-dub” heartbeat the heart valves make?

first: atrioventricular node (AV node)

second: sinoatrial node (SA node)

heart murmur

abnormal sounds produced by turbulence in blood when one or more valves fail to open or close completely and blood flows backwards

neurogenic

the heart beast under the control of signals from the nervous system (crustaceans)

myogenic

heart regulates their own contraction rhythm autonomously (insects and vertebrate), using pacemaker cells

What is the contraction of the cardiac muscle cells triggered by?

by action potentials that spread along the muscle cell membranes, sent through intercalated discs in cardiac muscle cells

sinoatrial node (SA node)

coordinates contractions of individual cardiac muscle cells, consists of pacemaker cells

pacemaker cells

• specialized cells in the upper wall of the right atrium

• ion channels in these cells open and close in a cyclic pattern that depolarizes and repolarizes their plasma membranes (causes contractions and relaxations) 

atrioventricular node (AV node)

• located in the heart wall between the right atrium and the right ventricle 

• cells in this node are excited by the atrial wave of contraction

• generate a signal that travels to the bottom of the heart via Purkinje fibers 

What does the short delay in transmission from the AV node to the ventricles allows?

allows the atria to finish contraction before the ventricles contract

electrocardiogram (ECG or EKG)

a machine used to detect electrical signals in the heart by attaching electrodes to different points on the surface of the body

blood pressure

the hydrostatic pressure exerted by the blood in vessels against the walls of the vessels

What is bp determined by?

• the force and amount of blood pumped by the heart

• the size and flexibility of the arteries 

Where is bp the highest in the body?

in arteries leaving the heart, it drops as blood passes from arteries to capillaries 

What is bp measured with?

sphygmomanometer

systolic blood pressure

the pulse, the peak of the increasing pressure as the ventricles contract

diastolic blood pressure

between ventricular contractions, arterial blood pressure reaches a low point

What is the normal range for systolic and diastolic bp?

• systolic bp: 90-120 mmHg 

• diastolic bp: 60-80 mmHg 

hypertension

• high blood pressure, a medical condition in which blood pressure is chronically elevated above normal values (at least 140/90)

• can damage arteries and lead to a heart attack or a stroke

What is the progression from arteries to veins?

arteries → arterioles → capillaries → venules → veins → vena cavas

What are the 3 major tissue layers of the artery walls?

1. outer layer: connective tissue containing collagen and elastic fibers that give the artery its recoil ability (keeps blood moving during diastole)

2. middle layer: thick layer of vascular smooth muscle cells, also mixed with elastin fibers

3. inner layer: endothelium- flattened cells

What are capillaries walls made of? What does it allow?

made up of a single layer of endothelial cells, allows for the exchange of gases, nutrients, and wastes with interstitial fluid 

What is blood flow through the capillaries controlled by?

by the contraction of smooth muscle in arterioles 

precapillary sphincter

a small ring of smooth muscle at the junction between an arteriole and a capillary that works to control the amount of blood flow to the capillaries 

What does the slow rate of blood flow in the capillaries allow for?

maximum time for the exchange of substances between blood and tissues

What do the narrow spaces between capillary endothelial cells allow to pass through? What doesn’t is allow?

water, ions, and other small molecules like glucose, doesn’t allow erythrocytes, platelets and plasma proteins to pass through, leukocytes can squeeze through 

blood brain barrier

capillary endothelial cells in the brain are tightly sealed together, which limits the exchange between capillaries and brain tissues

What are the two major mechanisms that drive capillary exchange?

1. diffusion along concentration gradients (gases)

2. bulk flow (water, ions, molecules, glucose)

Where is the concentration gradient for diffusion the greatest?

near the arterioles

What is bulk flow driven by?

blood pressure, which is higher than interstitial fluid pressure

Where is bulk flow the greatest why?

near arterioles because the pressure difference between bp and interstitial fluid pressures is the greatest 

What do the walls of venules and veins consist of?

• thinner than arterioles and arteries, less elastin as well

• have interior flaps of connective tissues that form one-way valves (keeps blood flowing to the heart)

• its thin walls can expand and contract over a relatively wide 

What does the expansion and contraction of the thins walls of veins and venules allows?

allows veins and venules to acts as blood reservoirs

How is the volume of the veins and venules adjusted?

by skeletal muscle contraction and valves in response to metabolic conditions and signal molecules

deep vein thrombosis

blood clots due to a lack of skeletal muscle activity 

atherosclerosis

plaques that form along artery walls, which reduce the vessel diameter and limits blood flow, leading to more issues 

What does atherosclerosis in the coronary arteries cause?

limited blood flow to cardiac muscle cells, leading to a heart attack

stroke

the blockage of arteries in the brain, leading to reduced blood flow to the brain

What are the 3 mechanisms for controlling bp?

• cardiac output

• degree of contraction of blood vessels (mainly arteries)

• total blood volume

baroreceptors

located in the walls of the blood vessels (cardiac muscle, aorta, and carotid arteries), where regulation of the heartbeat strength and rate starts, constantly provides info about bp 

What happens after the baroreceptors signal the medulla in the brain stem?

the brain stem sends signals via the autonomic nervous system that adjust the rate and the force of the force of the heartbeat

chemoreceptors

located in the aorta and carotid arteries, detect O2 content in the blood and influences cardiac output

How does a low and high O2 content in the blood affect the cardiac output?

• low O2 content = higher cardiac output 

• high O2 content = lower cardiac output