B3.2 Transport

Structure of capillary wall

One layer of endothelium cells with extracellular proteins that form the basement membrane. There are also pores between the endothelium cells, making it permeable to tissue fluid.

Tissue fluid

Substances in blood plasma except large protein molecules, including oxygen, glucose, ions, etc.

Function of tissue fluid

Tissue fluid flows between cells in a tissue, letting cells absorb useful substances and accumulating their waste products, before re-entering capillary network.

Lumen

Internal space of a tubular structure

Function of ateries

Carry high-pressure blood from the heart to organs

Structure of Arteries

• Thick wall

• Narrow Lumen

• Circular

• Visible fibres

Function of veins

Carry low pressure blood from organs to heart

Structure of veins

• Thin wall

• Wide lumen

• circular or flattened

• Little to no visible fibres

Layers of arterial walls

Tunica externa, tunica media, tunica intima

Tunica externa

Tough outer layer of connective tissue with collagen fibres

Tunica media

Thick layer containing smooth muscle and elastic fibers

Tunica intima

Smooth endothelium forming the lining of the artery

How can pulse be measured?

Counting manually or using a pulse oximeter

Pocket valves

Maintain circulation and prevent backflow of blood in veins

Adaptation of thin walls in veins

Allows muscle contraction to squeeze veins, which improves blood flow

Coronary arteries

Supply oxygenated blood from aorta to the heart wall

Occlusion

Blockage of coronary arteries by fatty deposits

Thrombosis

Formation of a blood clot, due to restricted blood flow and hardening of the artery

Xylem function

Transports water from roots to leaves in plants

Structure of xylem vessels

Cellulose mesh that forms hydrogen bonds with water → adhesion between water and cellulose of xylem vessels

Transpiration pull

Tension generated from cell walls drawing out water from xylem used to move water upwards

Adaptations of xylem vessels for water transport

• Long continuous tubes with minimal resistance

• Non-living vessels

• Lignified walls → have gaps for water to enter/exit

Phloem function

Transport of sugars from leaves to roots, transports carbon compounds bidirectionally

Cambium function

Production of xylem and phloem

Pith function

Stores nutrients and bulks out the stem

Cortex function

Stores food reserves, provides support, and does photosynthesis

Materials that move from tissue fluid into cells

• oxygen absorbed by diffusion

• Glucose absorbed by sodium-glucose cotransporters

• Amino acids by active transport

Materials that move from cells into tissue fluid

• Carbon dioxide by diffusion

• Waste products of metabolism

Role of Lymph ducts

Excess tissue fluid drains into lymph ducts to prevent tissue swelling

Structure of lymphatic vessels

• Narrow

• Permeable walls to tissue fluid

• Join up repeatedly to form wider vessels

Movement of lymph

Lymphatic vessels → merge with subclavian veins → vena cava → right side of the heart

Mammalian double circulation

Blood passes through the heart twice to make a full circuit

Systemic circulation

High pressure blood to organs except lungs

Pulmonary circulation

Low pressure blood to lungs

Single circulation of Fish

• Blood pumped to gills to be oxygenated

• Oxygen diffuses from water to blood

• Blood moves to other organs

• Deoxygenated blood returns to heart

Ventricles

Chambers with a strong muscular wall that generates high blood pressure when it contracts

Function of ventricles

Pumps blood into arteries

Atria

Chambers with thinner muscular wall that collect blood from veins

Function of atria

Pumps blood into ventricles

Atrioventricular (AV) valves

Valves between the atria and ventricles

Role of AV Valve

• close to prevent backflow of blood to the atria when ventricles contract

• open to allow blood flow from atria to ventricle

Semilunar valve

valves between the ventricle and the artery

Role of semilunar valve

• close to prevent backflow of blood to the ventricle when they relax

• open to allow blood flow from ventricles to the arteries when ventricles contract

Cardiac muscle

specialized muscle tissue that forms the wall of ventricles and atria

• branched → propagation of electric signal

SA Node (pacemaker)

Sends electrical signal into the atria, the interval of signals determines the heart rate (located in the right atrium)

AV node

Relays SA node signal to ventricle (stimulating contraction) through conducting fibers

Septum

wall of the heart between the left and right ventricles and between left and right atria

Role of septum

Prevents oxygenated and deoxygenated blood from mixing

Coronary vein

collect deoxygenated blood from heart wall and return to right atrium

Stages of the cardiac cycle

Atrial systole, ventricular systole, ventricular diastole

Atrial systole

• Atrium contracts, pressure increases, pumps blood from atrium to ventricle

• AV valve open

• Arterial pressure drops

Ventricular systole

• Ventricle contracts

• Pressure build-up → AV valve closes

• Ventricular pressure rises above arterial pressure → Semilunar valve opens

• Blood pumped from ventricle to artery

Ventricular diastole

• Ventricle stops contracting

• Ventricular pressure below arterial pressure → semilunar valve closes

• Ventricle pressure below atrial pressure → AV valve opens

• Blood flow from veins to atrium

Generation of root pressure in xylem

• Plant transpiration → tension draws water out of root cells to xylem vessels

• Active transport → xylem becomes hypertonic to cytoplasm → water moves into xylem by osmosis

Phloem tissue structure

• Sieve tubes provide channels for transport

• Adjacent cells connected by sieve plates

• Lack cellular content → rely on companion cells

Companion cells

Contain many mitochondria, provide ATP and sucrose to sieve tubes

What chamber of the heart is the vena cava connected to?

Right atrium

What chamber of the heart is the aorta connected to?

Left ventricle

What chamber of the heart is the pulmonary artery connected to?

Right ventricle

What chamber of the heart is the pulmonary vein connected to?

Left atrium

Blood flow through the heart

Vena cava → right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle

Types of AV valves

Tricuspid valve and bicuspid (mitral) valve

On which side of the heart is the tricuspid valve?

The right, separating the right atrium/ventricle

On which side of the heart is the bicuspid (mitral) valve?

The left, separating the left atrium/ventricle

Epidermis (stem)

Prevents water loss

Epidermis (roots)

Grows root hairs that increase surface area for water uptake