B3.2 Transport Flashcards
From where do capillaries receive their blood from?
They receive their blood from the smallest arteries called arterioles. Within body tissues and arteriole branches into what is called a capillary bed
What is a capillary bed?
This is a network of capillaries that all receive blood from the same arteriole. There are millions of arterioles and capillary beds in your body.
Draw a capillary bed, including the venule + arteriole
Where will the capillary bed drain it’s blood to?
It will drain its blood into the smallest of veins, called a venule
What is the lumen of a capillary?
The lumen is the inside diameter of a capillary, which is only large enough to accommodate one blood cell at a time
What is the structure of a capillary?
A capillary consists of a single-cell-thick inner tissue and a single-cell-thick outer tissue, making it highly permeable
Why are capillaries highly permeable?
Their thin, single-cell layers allow substances to pass through the membranes or between the membrane layers
What is highly vascular tissue?
Tissue that is enriched with capillary beds, often found in metabolically active parts of the body
What is the function of capillaries in tissues?
They exchange molecules between the blood and surrounding tissues. They also function like this in the lungs and gills
What are fenestrated capillaries?
These are capillaries with small slits or openings (fenestrations) that allow for increased permeability to larger molecules
Where are fenestrated capillaries commonly found?
In the kidneys + intestines, where rapid movement of molecules is necessary
How are capillaries adapted to their function?
- Having a small inside diameter
- Being thin walled
- Being permeable
- having a large surface area
- having fenestrations (in some)
How are arteries and veins identified?
They are identifies according to whether the vessel receives blood from the heart and takes that blood to a capillary bed (artery) or receives blood from a capillary bed and takes that blood back to the heart (vein)
Why are arteries lined with a thick layer of smooth muscle and elastic fibres?
This is because arteries receive blood directly from the heart and the blood is under relatively high pressure
Why are veins thin walled with a large lumen?
The lumen or arteries is relatively small compared to veins. Veins receive low pressure blood from capillary beds. They have this structure, with a large lumen to carry the slow-moving blood
What are arteries adapted to do?
This is to transport high pressure blood away from the heart.
How does the heart contribute to blood movement in arteries?
The heart contracts and relaxes rhythmically, sending surges of blood into arteries
What type of muscle is found in the walls of arteries?
Arteries contain a thick layer of smooth muscle
What controls the smooth muscle in arteries?
The autonomic nervous system (ANS) which regulates involuntary body functions. ANS = a part of nervous system that controls involuntary body functions, such as heart rate, blood pressure, digestion, and respiratory rate. It regulates smooth muscle, cardiac muscle, and glands without conscious control
How does smooth muscle in arteries help regulate blood pressure?
It changes the lumen diameter of arteries, controlling blood flow and pressure
Which proteins contribute to arterial elasticity?
Elastic and collagen
How do elastin and collagen help arteries withstand blood pressure?
They allow arteries to stretch when blood is pumped in and recoil after the surge, maintaining continuous blood movement
Why do arteries need to maintain high pressure?
High pressure ensures continuous blood flow between heartbeats
Where can you measure your own heartbeat?
- The carotid artery -> this is on either side of your trachea in your neck
- The radial artery -> this is on your wrist
What is pulse rate, and how is it felt in an artery?
Pulse (heart) rate is the number of heartbeats per minute. It is felt as a surge of pressure in an artery each time the heart contracts and pumps blood
What are veins?
Veins are blood vessels that return blood back to the heart after the blood has passed through a capillary bed.
What do veins do to account for the pressen and velocity blood loses in the capillary bed?
Blood loses a great deal of pressure and velocity in capillary beds. To account for this, veins have thin walls and a larger internal diameter. The unidirectional flow of the relatively slow-moving blood in veins is aided by internal valves that help prevent backflow of the blood. In addition, the thin walls of veins are easily compressed by surrounding muscles.
Which arteries supply blood to cardiac muscles?
The arteries that supply blood to cardiac muscle are called coronary arteries
What is a plaque, and how does it affect blood flow?
Plaque is a buildup of cholesterol and other substances in the lumen of arteries, leading to occlusion (restricted blood flow). Over time, this can significantly reduce blood flow and, if it occurs in a coronary artery, may cause a heart attack due to oxygen deprivation in the heart muscle
How do plants transport water and dissolved minerals without a heart?
Plants rely on tension force generated by transpiration to pull water and minerals upward from the roots
What is transpiration in plants?
Transpiration is the evaporation of water from leaves through open stomata, which creates tension that pulls water up the xylem
Where does transcribed water in leaves come from?
Water evaporates from the spongy mesophyll layer, moving into the air spaces and out through stomata
How does transpiration create movement of water in the xylem?
The loss of water by transpiration generates tension (negative pressure), pulling water from the xylem of nearby tissues by capillary action
What role does cohesion play in water movement in plants?
Cohesion allows water molecules to stick together, forming a continuous column that moves upward in the xylem
What is the cohesion-tension theory?
It explains how transpiration-driven tension and cohesion between water molecules enable water to move from roots to leaves in plants.
Describe formation of xylem tubes
Imagine many cylinder-shaped plant cells stacked upon eachother to make a long tube. When alive these cells would have have had complete cell walls. plasma membranes and typical plant organelles. Now, imagine that all of these cells die leaving behind only their thick cylinder-shaped cell walls. Even the end walls where the cells were joined to eachother in the tube completely or partially degenerate.
What does lignin provide?
The dead xylem tubes have cell walls protected with lignin for strength. The lignin provides resistance to collapse of the tubes because of the tension created by transpiration.
How does the structure of xylem help in water support?
The partial or total lack of cell walls between adjoining xylem cells allows for unobstructed upward water flow
What are pits in the xylem, and what is their function?
Pits are microscopic holes in the xylem’s sidewalls that allow water to move in and out as needed
Why is the absence of certain cell walls in xylem important?
It enables continuous water movement without resistance, facilitating efficient transpiration-driven transports
5 tissues in dicotyledonous stem + their functions
epidermis;prevents water loss and provides protection from microorganisms
cortex; an unspecialized cell layer that sometimes stores food reserves
Xylem; transport tubes that bring water up from the roots
phloem; transports carbohydrates, usually from leaves to other parts of the plant
vascular bundle; contains multiple vessels of both xylem and phloem
5 tissues in dicotyledonous root, and their functions
Epidermis; grows root hairs that increase the surface area for water uptake
Cortex; an unspecialized cell layer that stores food reserves
Xylem; transport tubes for water and minerals, starting in the roots
Phloem; transport tubes that receive sugars from leaves
vascular bundle; the area in the centre of the root containing xylem and phloem
What is tissue fluid, and why is it important?
Tissue fluid is the fluid that surrounds cells, allowing the exchange of substances between blood and cells. It helps transport oxygen, nutrients, and waste products
How is tissue fluid formed?
Tissue fluid is formed by pressure filtration at the arteriole end of a capillary bed, where high blood pressure forces plasma and small molecules out of the capillary walls
What is pressure filtration, and where does it occur?
Pressure filtration occurs at the arteriole end of the capillary bed, where high blood pressure forces plasma and dissolved nutrients through the capillary walls, forming tissue fluid
What happens to the tissue fluid after it has bathed the cell?
Most tissue fluid returns to the capillary at the venule end due to lower pressure, while some excess tissue fluid enters the lymphatic capillaries
What is the role of the lymphatic system in tissue fluid regulation?
The lymphatic capillaries collect excess tissue fluid that does not return to the blood and eventually return it to the circulatory system
How does blood pressure change across the capillary bed?
Blood pressure is high at the arteriole end, causing fluid to leave the capillaries, and low at the venule end, allowing tissue fluid to re-enter
Process of tissue fluid formation and reabsorption
- Blood enters the capillary bed from an arteriole with high pressure due to heart contractions
- Pressure filtration occurs at the arteriole end, where high blood pressure forces plasma (minus proteins and cells) though capillary walls, forming tissue fluid
- Tissue fluid surrounds nearby cells, allowing oxygen and nutrients to diffuse into the cells while carbon dioxide and waste diffuse out
- At the venule end of the capillary bed, blood pressure is lower and osmotic pressure pulls most of the tissue fluid back into the capillaries
- excess tissue fluid enters the lymphatic capillaries, where it is eventually returned to the circulatory system to maintain fluid balance
what is the circulatory system?
This is the body’s transport system responsible for moving blood, oxygen, nutrients, hormones, and waste products throughout the body. It consists of the heart, blood vessels (arteries, veins, capillaries), and blood
What are the main components of the circulatory system?
- heart; pumps blood throughout the body
- arteries; carry oxygen-rich blood away from the heart to tissues
- veins; carry oxygen-poor blood back to the heart
- capillaries - tiny blood vessels where exchange of gases, nutrients, and waste occurs between blood and tissues
- blood; the fluid that carries oxygen, nutrients, hormones and waste
What are the different types of circulation in the body?
- Systemic circulation; sends oxygenated blood from the heart to the body and returns deoxygenated blood back to the heart
- Pulmonary circulation; carries deoxygenated blood from the heart to the lungs for oxygenation and returns oxygenated blood to the heart
Lymphatic circulation; Works alongside blood circulation, returning excess tissue fluid (lymph) to the bloodstream
How are blood plasma and tissue fluid similar in composition?
Blood plasma and tissue fluid have a similar chemical makeup because capillary membranes are highly porous, allowing substances like water, nutrients, oxygen, and waste products to pass freely between the blood and surrounding tissues
Why do red blood cells and large proteins remain in the bloodstream?
Red blood cells and large plasma proteins cannot pass through capillary walls because they are too large to fit though the small pores in the capillary membranes. This keeps them inside the blood vessels
Can white blood cells pass into the tissue fluid?
Yes, some white blood cells can squeeze through capillary walls and enter tissue fluid, allowing them to fight infections and defend against pathogens in body tissues
What role does capillary pressure play in tissue fluid formation?
The high pressure at the arteriole end of the capillary bed forces plama (minus cells + large proteins) out, forming tissue fluid that surrounds body cells for nutrient and waste exchange
Why do blood cells need a constant supply of oxygen and nutrients?
Cells require oxygen and nutrients for energy production and metabolic processes. They also produce waste products like carbon dioxide and urea, which must be removed
What is facilitated diffusion, and how does it work?
Facilitated diffusion is the passive movement of molecules across a cell membrane through protein channels, following their concentration gradient. This occurs for substances like glucose and oxygen
How do capillary membranes differ from plasma membranes of body cells?
Capillary membranes are very porous, allowing substances to pass freely, whereas cell membranes regulate ion movement using active transport mechanisms
What role does ATP play in ion transport?
ATP powers active transport mechanisms to maintain high potassium inside cells and high sodium cells, keeping ion concentrations balanced
What happens to tissue fluid that does not re-enter the capillary bed?
It enters the lymphatic capillaries, small thin-walled tubes that collect excess tissue fluid and prevent fluid buildup around body cellst
What is lymph, and how is it formed?
Lymph is the fluid that enters lymphatic capillaries from the surrounding tissue. It consists of excess tissue fluid, containing water, solutes, and some immune cells
How are lymphatic capillaries adapted for fluid movement ?
they have thin walls with gaps between adjoining cells, allowing easy movement of water and solutes into the lymphatic system
How are lymph vessels similar to veins?
They contain internal one-way valves to keep fluid moving in one direction. They rely on skeletal muscle contractions to help move fluid through the system. They merge into larger lymph ducts, eventually returning fluid to the bloodstream
What is the main difference between single circulation and double circulation?
Single circulation passes blood through the heart once per cycle, while double circulation passes blood through the heart twice per cycle, maintaining high pressure
How does the circulatory system of fish work?
-Fish ahve a 2-chambered heart (one atrium, one ventricle)
blood is pumped from the heart to the gills for oxygenation. oxygenated blood then moves to body organs, where it delivers oxygen. Deoxygenated blood returns directly to the heart, completing one circuit
What is the main limitation of the fish circulatory system?
Blood loses pressure after passing through the gills, leading to slower circulation and less efficient oxygen delivery to organs
How does the double circulatory system in mammals work?
Mammals have a four-chambered heart, which separates oxygenated and deoxygenated blood, ensuring efficient circulation:
Pulmonary circulation – Deoxygenated blood is pumped to the lungs via the pulmonary artery, where it is oxygenated.
Systemic circulation – Oxygenated blood returns to the heart via the pulmonary vein and is pumped to body organs through the aorta.
Deoxygenated blood returns via the vena cava, completing the cycle.
Why is double circulation more efficient than single circulation?
The heart restores blood pressure after passing through the lungs, allowing faster oxygen delivery.
Blood is pumped separately to the lungs and body, preventing oxygenated and deoxygenated blood from mixing.
Mammals require higher energy for movement and metabolism, making efficient circulation essential.
What are the two major routes of blood circulation in the mammalian heart?
Pulmonary circulation – The right side of the heart pumps deoxygenated blood to the lungs for oxygenation and then back to the heart.
Systemic circulation – The left side of the heart pumps oxygenated blood to body tissues and returns deoxygenated blood to the heart.
What is the advantage of the double circulation system in mammals?
It ensures that both lung capillaries and body capillaries receive blood at a high enough pressure for efficient exchange of oxygen, nutrients, and waste. This also allows pressure filtration to occur in all capillaries.
Adaptations for efficient blood flow
- Cardiac muscle; a highly vascular tissue making up the heart muscle. This muscle is especially thick in the ventricles of the heart. The muscle making up the wall of the left ventricle is the thickest, as it pumps blood out to locatios in the entire body
- A pacemaker; known as sinoatrial node. An area of specialized cells in the right atrium generate a spontaneous electrical impulse to start each heartbeat.
-Atria; thin muscular chambers of the heart designed to receive low pressure blood from the capillaries of the longs or body tissues by way of large veins entering the heart. The atria send blood to the ventricles. - Ventricles; thick muscular chambers that pump blood out under pressure to the lungs or body tissues
- Atrioventricular valves; valves located between the atria and ventricles that close each heart cycle to prevent any backflow of blood into the atria
- Semilunar valves; valves that close after the surge of blood into the pulmonary artery or aorta, to prevent backflow of blood intro the ventricles
- Septum; a wall of muscular and fibrous tissue that seperates the right sides of the heart from the left side
-Coronary vessels; blood vessels that provide oxygenated blood to the heart muscle
What is the cardiac cycle?
the cardiac cycle is a series of events in one heartbeat, including contraction (systole) and relaxation (diastole) if the heart chamber
How is the heart rate related to the cardiac cycle?
The heart rate is the number of cardiac cycles per minute. For example, a heart rate of 72 beats per minute means 72 cardiac cycles occur per minute.
What is systole, and what happens during it?
Systole is the contraction phase of the heart, where pressure increases, and blood is pushed out of the chamber.
What is diastole, and what happens during it?
Diastole is the relaxation phase of the heart, where the chambers fill with blood, and the cardiac muscle is relaxed.
How does the SA node control heart contractions?
The SA node spontaneously generates action potentials that spread through the atria, causing them to contract (atrial systole).
What is the atrioventricular (AV) node), and what does it do?
The AV node, located in the right atrium, receives impulses from the SA node and transmits them to the ventricles, ensuring a coordinated contraction.
How does the heart generate its own electrical impulses?
The heart is myogenic, meaning it generates its own electrical activity without needing nervous system stimulation.
What is the difference between atrial systole and ventricular systole?
-Atrial systole: Both atria contract first, pushing blood into the ventricles.
Ventricular systole: Both ventricles contract shortly after, pumping blood to the lungs and body.
What role does the AV node play in the cardiac cycle?
The AV node receives the electrical impulse from the SA node and delays it by 0.1 seconds before sending action potentials to the ventricles, ensuring proper timing of heart contractions.
Why does the AV node delay the electrical impulse?
The 0.1-second delay allows the atria to fully contract and empty blood into the ventricles before ventricular contraction begins.
How does the AV node ensure efficient contraction of the ventricles?
The AV node sends impulses through conducting fibers that travel down the septum and branch out into the ventricular walls, ensuring that both ventricles contract (systole) simultaneously.
Why do ventricles require a specialized conduction system?
The ventricular walls are thicker than the atrial walls, requiring an efficient system of conducting fibers to rapidly transmit impulses and ensure coordinated contraction.
What is an electrocardiogram?
this is a graph plotted in real time, with electrical activity (from SA+AV nodes) plotted on the y-axis and time on the x-axis. Electrical leads are placed in a variety of places on the skin in order to measure small voltage given off by these two nodes of the heart. Every repeating pattern on an ECG is a representation of one cardiac cycle.
How can plants move water into their roots even when transpiration is not occurring?
Plants can absorb water through their roots in early spring (before leaves grow) or in humid conditions, suggesting an alternative mechanism to transpiration-driven movement.
What is osmosis, and how does it help water uptake in roots?
Osmosis is the movement of water from high to low water potential through a membrane. Root cells actively transport mineral ions, creating a low water potential that draws water into the root hairs.
How do mineral ions aid in water movement in the root?
Mineral ions are actively transported into root cells, reducing water potential and causing water to enter via osmosis. This process creates positive fluid pressure that pushes water upward.
What tissues do water and minerals pass through to reach the xylem?
Water and dissolved minerals pass through the epidermis, cortex, and into the xylem tissue in the center of the root.
What is phloem, and what does it transport?
Phloem is vascular tissue that transports sugar-rich sap from one part of the plant to another.
What is the source-to-sink movement in phloem?
Sugars move from a source (sugar producer, e.g., leaves) to a sink (sugar consumer or storage, e.g., roots, buds, fruits).
What adaptations do phloem sieve tubes have for translocation?
- Sieve plates allow efficient flow of sap.
Reduced cytoplasm & no nucleus to minimize resistance.
Companion cells with mitochondria provide ATP for active transport.
Plasmodesmata connect sieve tubes for easy exchange.
Can plant structures act as both a source and a sink?
Yes. For example, potatoes act as sinks in summer (storing sugar) and as sources in spring (breaking down stored sugar).
What are the two main types of cells in phloem?
Sieve tube elements (which transport sap) and companion cells (which support sieve tubes by providing ATP and proteins).
What is the function of sieve tube elements?
They form a tube-like structure for sap transport. They lack a nucleus and most organelles to reduce resistance to fluid movement.
Why do sieve tube elements rely on companion cells?
Sieve tube elements lack a nucleus and major organelles, so companion cells provide them with ATP, proteins, and metabolic support.
What is the role of plasmodesmata in phloem cells?
Plasmodesmata are small channels connecting companion cells and sieve tubes, allowing sugars and molecules to pass between them.
What is translocation, and why is it important?
Translocation is the movement of sugars (sap) in phloem from a source (sugar-producing organ) to a sink (sugar-storing/using organ).
How do companion cells load sugars into sieve tube elements?
Companion cells actively transport sugars into sieve tubes, creating an area of low water potential inside the sieve tube.
How does water help in phloem translocation?
Water enters the sieve tube from xylem by osmosis, increasing pressure inside the tube and pushing the sugar-rich sap along the phloem.
What happens at the sink in phloem transport?
Sugars are unloaded from the sieve tubes at the sink, where they are either used (e.g., in respiration) or stored (e.g., as starch).
How does water move within the sieve tube elements of the phloem?
Water moves toward the area of lowest pressure, which is where sugars are being unloaded at the sink.
What happens to sugars when they reach the sink in phloem transport?
Sugars are unloaded from the sieve tube elements into companion cells and then into surrounding tissues where they are used for energy or stored.
How does water return to the xylem from the phloem?
At the sink, solutes (sugars) are removed, creating a high water potential inside the phloem. Water then moves back into the xylem by osmosis.
