Animal Transport system: Circulatory and respiratory

Circulatory Systems

Essential for linking exchange surfaces with cells throughout the body, facilitating the transport of nutrients, gases, and waste.

Diffusion

The process by which small molecules move between cells and their surroundings, effective only over short distances due to the time it takes to diffuse being proportional to the square of the distance.

Open Circulatory Systems

Found in insects and some mollusks, utilize hemolymph that bathes organs directly, allowing for lower energy expenditure.

Closed Circulatory Systems

Present in annelids, cephalopods, and vertebrates, confine blood to vessels, enabling more efficient transport of oxygen and nutrients.

Components of Circulatory Systems

Consists of a circulatory fluid (blood or hemolymph), a set of interconnecting vessels, and a muscular pump (the heart).

Cardiovascular System

In vertebrates, includes arteries, veins, and capillaries, with blood flowing unidirectionally through these vessels.

Arteries

Carry blood away from the heart, branching into arterioles and eventually leading to capillary beds where exchange occurs.

Vertebrate Hearts

Typically have two or more chambers, with blood entering through atria and exiting through ventricles.

Single Circulation

Seen in fish, involves blood passing through two capillary beds before returning to the heart.

Double Circulation

Found in amphibians, reptiles, and mammals, separates oxygen-rich and oxygen-poor blood into distinct circuits.

Three-Chambered Heart

Possessed by frogs, directs blood flow based on oxygen needs, with a ridge in the ventricle separating oxygen-rich and oxygen-poor blood.

Four-Chambered Heart

Found in mammals and birds, ensuring complete separation of oxygenated and deoxygenated blood, crucial for high metabolic demands.

Advantages of Closed Circulatory Systems

Support larger body sizes and more active lifestyles by providing efficient oxygen and nutrient delivery.

Blood Flow in Mammals

Involves a systematic flow from the right ventricle to the lungs via pulmonary arteries, where gas exchange occurs.

Aorta

Branches into various arteries, supplying oxygen to different body regions, including the coronary arteries that nourish the heart.

Capillary Beds

Sites of gas exchange, where oxygen diffuses from blood to tissues, and carbon dioxide diffuses from tissues to blood.

Structure of Capillaries

Being one cell thick, facilitates efficient diffusion of gases and nutrients.

Venules

Collect blood after passing through capillaries, which converge into veins returning to the heart.

Human heart

Approximately the size of a clenched fist, primarily composed of cardiac muscle, which is specialized for continuous contraction and relaxation.

Chambers of the heart

The heart consists of four chambers: two atria and two ventricles.

Atria

Have thinner walls and function as collection chambers for blood returning from the body and lungs.

Ventricles

Have thicker muscular walls, enabling them to contract forcefully and pump blood out of the heart into the systemic and pulmonary circuits.

Cardiac cycle

Consists of two main phases: systole (contraction) and diastole (relaxation).

Systole

The phase during which the heart pumps blood.

Diastole

The phase during which the heart fills with blood.

Cardiac output

The volume of blood pumped per minute, determined by heart rate (beats per minute) and stroke volume (amount of blood pumped per contraction).

Heart valves

Four valves (atrioventricular and semilunar) that prevent backflow of blood, ensuring unidirectional flow through the heart chambers.

Heart sounds

The characteristic 'lub-dup' sound of the heartbeat produced by the closure of the atrioventricular valves (lub) and the semilunar valves (dup).

Heart murmur

An abnormal sound that can occur due to backflow of blood through defective valves, indicating potential heart issues.

Autorhythmicity

Some cardiac muscle cells can contract independently of nervous system signals, allowing for a consistent heart rhythm.

Sinoatrial (SA) node

Known as the pacemaker, it initiates impulses that set the heart rate and timing of contractions.

Atrioventricular (AV) node

Where impulses from the SA node are briefly delayed before being transmitted to the ventricles via Purkinje fibers.

Purkinje fibers

Fibers that ensure coordinated contraction by transmitting impulses to the ventricles.

Autonomic nervous system

Influences the heart's pacemaker activity; the sympathetic division increases heart rate, while the parasympathetic division decreases it.

Electrocardiogram (ECG)

The electrical impulses generated during the cardiac cycle can be recorded as an ECG, providing insights into heart health and rhythm.

Blood vessels

All blood vessels consist of a central lumen lined with a smooth epithelial layer (endothelium) that minimizes resistance to blood flow.

Arteries

Have thick, elastic walls to withstand high pressure from blood pumped from the heart.

Veins

Have thinner walls and contain valves to prevent backflow.

Blood flow velocity

Decreases as blood moves from arteries to arterioles to capillaries due to increased resistance and total cross-sectional area.

Blood pressure

The force exerted by circulating blood on the walls of blood vessels, with systolic pressure being the highest during ventricular contraction and diastolic pressure being the lowest during relaxation.

Regulation of blood pressure

Regulated through homeostatic mechanisms that alter the diameter of arterioles, with vasoconstriction increasing pressure and vasodilation decreasing it.

Nitric oxide (NO)

Induces vasodilation.

Endothelin

A potent vasoconstrictor.

Capillary exchange

Capillaries are the sites of material exchange between blood and interstitial fluid, facilitated by their thin walls composed of endothelium and basal lamina.

Lymphatic system

Plays a crucial role in returning fluid lost from capillaries back to the bloodstream, with lymph being the fluid that leaks out.

Lymph nodes

Filter lymph and are integral to the immune response, often swelling during infections as they produce more immune cells.

Edema

Swelling caused by disruptions in lymphatic flow or imbalances in fluid exchange, leading to excess fluid accumulation in tissues.

Open circulatory systems

Have fluid that is continuous with the surrounding interstitial fluid, allowing for direct exchange of materials with body cells.

Closed circulatory systems

Contain blood, a specialized fluid that circulates within vessels, providing efficient transport of nutrients, gases, and waste.

Blood

A connective tissue composed of cells suspended in a liquid matrix known as plasma, which constitutes about 55% of blood volume.

Cellular components of blood

Include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets, which together occupy approximately 45% of blood volume.

Plasma

Contains dissolved inorganic salts (electrolytes) that help maintain osmotic balance and blood pH.

Plasma proteins

Play crucial roles in lipid transport, immune responses, and blood clotting, with a higher protein concentration compared to interstitial fluid.

Erythrocytes

Responsible for oxygen transport, containing hemoglobin that binds up to four O2 molecules per protein.

Leukocytes

Involved in immune defense, with five major types that either phagocytize pathogens or mount immune responses.

Platelets

Cell fragments essential for blood clotting, preventing excessive bleeding.

Sickle-cell disease

Results from abnormal hemoglobin, causing red blood cells to deform into a sickle shape, leading to blockages and reduced oxygen transport.

Coagulation

The process of forming a solid clot from liquid blood, initiated by a cascade of reactions converting fibrinogen to fibrin.

Thrombus

A blood clot that forms within a blood vessel, potentially obstructing blood flow and leading to serious health issues.

Cardiovascular diseases

Encompass a range of disorders affecting the heart and blood vessels, from minor issues to life-threatening conditions.

Atherosclerosis

Involves the buildup of plaque in arteries, leading to inflammation and potential heart attacks or strokes.

Low-density lipoprotein (LDL) cholesterol

High levels increase the risk of heart disease.

High-density lipoprotein (HDL)

Helps remove excess cholesterol.

Gas exchange

Refers to the uptake of O2 and the discharge of CO2, essential for cellular respiration.

Partial pressure gradients

Drive the movement of gases, with O2 being less soluble in water than in air, necessitating efficient respiratory systems in aquatic animals.

Respiratory surfaces

Gas exchange occurs across specialized respiratory surfaces, which vary among animals and include skin, gills, tracheae, and lungs.

Gills

Specialized structures that provide a large surface area for gas exchange, utilizing a countercurrent exchange system to maximize O2 uptake.

Countercurrent exchange system

In fish, blood flows in the opposite direction to water, ensuring that blood is always less saturated with O2 than the water, allowing for efficient gas exchange.

Ventilation

Crucial for maintaining the partial pressure gradients necessary for gas exchange, achieved by moving water over gills or air into lungs.

Gas Exchange in Aquatic Animals

Fish gills are specialized structures for gas exchange in water, allowing oxygen to diffuse from water into the blood and carbon dioxide to diffuse out.

Gills

Composed of thin filaments and lamellae, increasing the surface area for gas exchange.

Countercurrent exchange mechanism

Maximizes oxygen uptake; water flows over gills in the opposite direction to blood flow, maintaining a gradient for diffusion.

Salmon gill function

Can adapt their gill function based on the oxygen levels in their environment.

Tracheal System in Insects

Consists of a network of branching tubes that deliver oxygen directly to body cells, bypassing the circulatory system.

Active ventilation in larger insects

Must actively ventilate their tracheal system to meet higher oxygen demands, using abdominal movements to push air in and out.

Efficient gas exchange in tracheal systems

Oxygen diffuses directly to tissues without the need for a circulatory intermediary.

Grasshopper ventilation

Exhibit rapid ventilation during flight to meet increased metabolic demands.

Lungs

Infoldings of the body surface that facilitate gas exchange in terrestrial animals.

Circulatory system's role in gas exchange

Transports gases between the lungs and the rest of the body, ensuring efficient oxygen delivery.

Human lung structure

Includes bronchi, bronchioles, and alveoli, optimizing surface area for gas exchange.

Mammalian respiratory mechanics

Air enters through the nostrils, where it is filtered, warmed, and humidified before reaching the lungs.

Pharynx

Serves as a pathway for air to the lungs and food to the stomach, with the epiglottis preventing food from entering the trachea.

Gas exchange in alveoli

Occurs where oxygen diffuses into the blood and carbon dioxide diffuses out.

Mucus escalator mechanism

Helps clear debris from the respiratory tract, maintaining lung health.

Positive pressure breathing

Used by amphibians like frogs, forcing air into the lungs by compressing the mouth cavity.

Bird respiratory system

Possesses air sacs that allow for unidirectional airflow, enhancing oxygen extraction efficiency.

Bird ventilation cycle

Requires two cycles of inhalation and exhalation, ensuring a constant supply of fresh air through the lungs.

Mammalian negative pressure breathing

Where the diaphragm and rib muscles contract to expand lung volume and draw air in.

Inhalation and exhalation in mammals

Inhalation is an active process, while exhalation is typically passive due to elastic recoil of lung tissues.

Tidal volume

Refers to the amount of air inhaled with each breath.

Vital capacity

The maximum amount of air that can be exhaled after a deep inhalation.

Residual volume

Remains in the lungs after exhalation, ensuring that gas exchange can continue even between breaths.

Control of breathing in humans

Regulated by the medulla oblongata, which adjusts the rate and depth of breathing based on pH levels in the cerebrospinal fluid.

Sensors in the medulla

Monitor oxygen and carbon dioxide levels, providing feedback to the respiratory centers.

Role of pons in breathing

Plays a role in modulating breathing patterns, ensuring a coordinated respiratory response.

Breathing during exercise

Increased carbon dioxide levels trigger faster breathing to enhance oxygen intake.

Respiratory pigments

Proteins that transport oxygen in the blood, such as hemoglobin.

Hemoglobin

A respiratory pigment that binds oxygen cooperatively, increasing the affinity of remaining sites for oxygen.

Bohr shift

Describes how increased carbon dioxide levels lower blood pH, reducing hemoglobin's affinity for oxygen, promoting oxygen release where it is needed most.

High-altitude adaptations

Adaptations in hemoglobin that allow for better oxygen uptake despite lower atmospheric oxygen levels.