Animal Physiology: Circulatory System

ANP102 Course Details

• The lecturers for ANP102 are Dr. M. O. Abioja (Course Coordinator), Dr. O. F. Smith, and Prof. O. M. Onagbesan.
• The course schedule includes topics from the nature of living things to reproductive systems in mammals and birds.
• A continuous assessment test is scheduled for week 11.

Animal Physiology

• Animal physiology covers physiological systems in mammals and birds, the nature and activities of living things.

Circulatory System Overview

• All living organisms need to transport nutrients, wastes, and gases.
• Single-celled organisms facilitate this via the cell surface, while multicellular organisms use specialized transport and circulatory systems.
• Sponges, the simplest animals, possess a transport system.
• Simple animals, such as hydra and planaria, lack specialized organs, using their skin for transportation.
• Larger organisms need specialized organs and organ systems to fulfill these requirements.

Circulatory System Components

• The circulatory system comprises of blood, the heart, and blood vessels.
• Blood constitutes a connective tissue of liquid plasma and cells.
• The heart acts as a muscular pump to transport blood.
• Blood vessels, including arteries, capillaries, and veins, deliver blood to all tissues
• Multicellular organisms do not have most of their cells in contact with the external environment.

Types of Circulatory Systems

• Open circulatory systems are common in molluscs and arthropods, with evolution in insects, mollusks, and invertebrates.
• Blood, pumped into a hemocoel, diffuses back to the circulatory system between cells.
• The heart pumps blood into body cavities, where tissues are surrounded by it with sluggish blood flow.
• Closed circulatory systems appear in vertebrates and some invertebrates.
• In closed systems, blood remains within the vessels of varying sizes and wall thicknesses.
• A heart pumps blood through vessels, not filling body cavities and enabling fast blood flow.
• The human closed circulatory system is generally known as the cardiovascular system.
• The lymphatic circulation represents a secondary circulatory system that gathers fluid and cells, returning them to the cardiovascular system.

Vertebrate Cardiovascular Systems

• This comprises a heart able to propel blood through arteries and back via veins.
• The atrium, the heart's upper chamber, receives blood.
• Passing though a valve, blood enters the ventricle, the lower chamber.
• Ventricle contraction forces blood into an artery, with heart muscle being composed of cardiac muscle cells.
• Arteries transport blood away from the heart and have walls able to expand and contract.
• Arteries have three thick walls with strong smooth muscle and elastic connective tissue, which can carry blood under high pressure.

Arteries

• The aorta serves as the main artery leaving the heart.
• The pulmonary artery is unique as it carries oxygen-poor blood.
• It conveys deoxygenated blood to the lungs, where gas exchange takes place, with carbon dioxide diffusing out and oxygen diffusing in.
• Arterioles act as small arteries connecting larger arteries with capillaries.
• Arterioles branch into capillary beds.

Capillaries

• Capillaries represent thin walled blood vessels to facilitate gas exchange.
• The capillary wall is one cell layer thick and are part of dense capillary beds.
• Small pores exist between the capillary wall, allowing material and white blood cell passage.
• Blood flow is regulated in capillary beds by nerve-controlled sphincters.
• Blood pressure fluctuates across all vessels of the circulatory system.
• Nutrients, wastes, and hormones are exchanged across the thin capillary walls.
• Capillaries function at a microscopic size.

Circulatory System Functions and Exchange

• The system delivers oxygen, nutrients, molecules, and hormones, removing carbon dioxide, ammonia, and metabolic waste.
• Capillaries facilitate the point of exchange between blood and surrounding tissues.
• Materials move in and out of capillaries by passing through or between the cells.
• An extensive capillary network exists, with an estimation of 50,000 to 60,000 miles long in the human body.
• Blood can bypass capillary beds using thoroughface channels.
• Muscles control channels causing them to open and close which regulates blood flood.

Veins and Venules

• Blood flows from capillary beds into progressively larger venules, which join to form veins.
• Veins transport blood from capillaries to the heart.
• With the exception of the pulmonary veins, venous blood usually has low oxygen.
• Pulmonary veins carry oxygenated flood and move it away from the lungs towards the heart.
• Venules are smaller veins that gather blood from capillary beds into veins.
• Low pressure is found in veins, so movement depends on nearby muscular contractions.
• Valves also exist in veins which prevents the back-flow of blood.

Blood Pressure

• Ventricular contraction propels blood into arteries under great pressure.
• Blood pressure is measured in mm of mercury.
• For healthy young adults ventricular systole is at 120mm, and 80 mm at ventricular diastole.
• High blood pressure (human 120/80 ) signifies higher speed in blood circulation (20 seconds in humans).
• Pressure lessens as blood moves further away.
• Each ventricle contraction causes pressure through the arteries.
• Elasticity in the lungs helps keep pulmonary pressures low.
• Systemic pressure is sensed by receptors in the arteries and atria.
• Nerve impulses communicate to the medulla region of the brain.
• Signals the medulla which regulates blood pressure .

Vertebrate Vascular Systems Diversity

• Humans, birds, and mammals share a four-chambered heart which separates oxygen-rich and oxygen-depleted blood fully.
• Fish have a two-chambered heart.
• Amphibians have a three-chambered heart with two atria and one ventricle.
• The disadvantage of having their chambered hearts is they mix the oxygenated and deoxygenated blood together .
• Some reptiles have the partial separation of a ventricle.
• Many reptiles + all birds and mammals have a four-chambered heart, for complete separation of both systemic and pulmonary circuits.

The Heart - A Muscular Pump

• It acts as a muscular pump that contracts and the forms vary.
• Forms may include chambered hearts seen in mollusks/vertebrates and tubular hearts of arthropods.
• It may also have Aortic arches of annelids.
• Insects have accessory hearts that supplement the main heart via pumping.
• Amphibians + reptiles, have lymph hearts, this assists in pushing lymph back into veins.
• The vertebrate heart, e.g. in fish, has chambers such as an auricle and one ventricle.
• Auricles recieves blood.
• Ventricles pumps blood that gets to it from the auricle out through a valve towards gills through an artery.
• Amphibians have two atria which leads to a single common ventrical forming a three-chambered hearts.
• A partial separation occurs in some the ventricle to lessen any mixing between oxygenated/deoxygenated blood.
• Two-sided or two chambered hearts permit pumping at higher pressures.
• Addition of a the pulmonary loop to support movement of blood to the lungs and permits lower pressure.

Heart and Visceral Organs

• The heart's relation to major visceral organs is essential for cardiovascular performance.

The Heart's Work

• Four-chambered hearts supporting pulmonary and systemic circuits allow for more metabolic rate needing for being warm-blooded.
• It has atrioventricular (AV) valves that split an auricle away from it's ventrical.
• They include semilunar (or arterial) valves, this separates every ventricle from the connecting artery.
• Normal heart beat = 70BPM.
• It also supports the cardiac cycle.
• Humans will undergo over 3 billion contraction cycles.
• Cardiac cycle has two-parts: systole (heart muscle contraction) and diastole (relaxation of the heart muscle).
• Atria contracts while ventricles relax.
• Pulses is a wave action resulting from the initial heart contractions.
• All heart valves open and close as needed during its activity.

Heart sounds

• Heart muscle experiences continual contraction via nodal tissue localized within the heart region.
• This initiates the heartbeat (SA node sinoatrial node ).
• This is aided through AV node (atrioventricular node or pacemaker) and heartbeats that also utilize messages derived autonomic nervous system functions.
• Heart valve also regulates unilateral floods/one way floods that support atrial ventricular contraction cycle.

What is blood?

• It's a special component within our body that goes back + forth and aids normal cardiac process.
• Cardiac cycle (every beat) occurs for up to 0.8 seconds .
• Deoxygenated blood goes from the body to vena cava and reaches your right atria , while also taking in the oxygenated blood away from lungs.
• Muscles in both regions (atria) are also pushing blood thru every AV valve into all of the ventricles during its activity/pumping.
• Diastole = filling ventricles byblood at all times for every heart rotation .
• Ventricular systole = SL valves opening from the heart + then blood going outwards , by pulmonary + aorta movements.
• We can also observe how sound from every heart muscles functions + the valves supporting the "lub-dub" sounds.
• "Lub" describes closure between AV valvues, meanwhile "dub" marks the closure coming out of the SL valves.
• Near the right atria, the heartbeats comes with sinoatrial nodes (SA nodes ) nearby and muscles also contract as needed.
• They send some signal for other components to trigger or contract to perform task as scheduled in all parts .
• Bundle of His fibres + Purkinjie fibers are stimulated before hearts perform its functions and perform signals in the ventricles.

Coordinated Action

• Coordinated heart cell contractions synch up to beat as one.

Heart and Cardiovascular System Diseases

• Cardiac muscle cells in order to carry oxygenated flood uses of arteries.
• With exercises, these arteries deliver greater/higher than x5 the normal flood from the system .
• blocked coronary artery = heart muscle being non-functional.
• Usually its the buildup of fatty-acids+ cholesterol inside lumen the coronary system.
• Chest aches can results periods that have extra stress/exertion.
• We call this is angina pectoralis.
• Since heart muscles do not divide, the cells that die is not replaced..

Controllable Disease

• Hypertension: blood with the pressure exceeding 140/90.
• If undiagnosed or under control it may cause stress/genetical risks factors/alcohol & obesity ,etc.
• Its usually very manageable if its taken care of by licensed physicians.

Circulation

• The system has 2 main flows, known to the pulmonary, and the systemic route that has oxygenated cells in the body.
• Through coronary arteries the nutrients and other cells reach those functional areas ,which makes for the portal design in the system.

Blood Components

• Liquid and cell fragmentation happen inside of the red region (where fragments and molecules flow out together.)

What is Plasma?

• It makes 60% of the flood by volume. it also contains + releases components
• Including hormones ions fluids carbohydrates, some of these can acts just normal or can be affected by its surroundings).
• So proteins and cholesterol can move more freely within the blood cells.

What is Blood? (Cells Overview)

• It makes up parts that are small from blood (such erythrocytes and rbc's).
• Its typically in all components where they are created in bone.
• Bone skull pelvis ribs, and sometimes also the vertebral regions .
• Its lasts within 120 day, that later gets discharged after utilization .
• Iron components that is removed are reused + heme regions of liver is functional as a way to separate, and create bile after.
• Usually x2 million + every seconds for new replacement by similar or replacement cell compounds.

What is Blood? (What about lack haemoglobin?

• Leukocyctes assist the blood system for immune functions purposes
• They make 1% in total, usually is located at the stem region of our bones
• There is mainly neutrophils to the cells that are used with fluid, or they will absorb any substance if needed.
• It takes the macro size regions to increase all cell functions that makes WBC or create B-cells.
• There is various other kinds such as the T group and B group.
• While antibodies are functional with macrophage (white blood cells that squeeze thru vessels for fighting conditions.

What is Blood? What about the Blood Platelets?

• blood clot is made from fragmented regions that has several essential pieces
• including but are not always just cells by the damaged tissue.
• For approximately half-month+ the platelets will restore the cells again later on,.
• While they do so we can observe adherence occurs or when blood release more substance within vessels.
• Blood is not always capable in haemophilaic.

Lymphatic System Overview

• Fluids are forced in, such intercellular spaces, (as blood floods out from vessels
• Transports cell matters.
• It can support in secondary circuits as needed