Blood, Capillaries and Transport

• No cell is more than 2-3 cells away from a capillary bed.
• Blood transports nutrients, hormones, antibodies, waste products, and heat to and from cells.
• Diffusion takes time for transport within the body.

Types of Blood Vessels

• Arteries carry high-pressure blood away from the heart to the organs in pulses.
• Veins carry low-pressure blood from organs back to the heart.
• Capillaries facilitate the exchange of materials between the blood and the internal or external environment.

Artery Structure

• Composed of three layers: Tunica Externa, Tunica Media, and Tunica Intima.
• Tunica Externa consists of connective tissue with collagen.
• Tunica Media consists of smooth muscle and elastin.
• Tunica Intima consists of smooth endothelium.
• Elastin fibers store potential energy when stretched, recoiling to squeeze blood and reduce energy needs.
• Collagen fibers have high tensile strength.
• Elastin and collagen fibers allow arteries to withstand high and variable blood pressures.

Capillary Characteristics

• Thin and narrow in diameter.
• Branching structure provides a large total surface area.
• Permeable walls.
• Transports blood through almost all tissues in the body, except the eye lens and cornea.
• Consist of one layer of endothelium cells with a basement membrane of extracellular fibrous proteins
• Pores between endothelium cells allow some fluid to leak, enabling passage of small to medium-sized particles but not macromolecules.
• White blood cells can pass in certain places.
• Leaked fluid, similar to tissue fluid or plasma, contains oxygen and glucose.
• Fenestrated capillaries have large pores which speeds up exchange.
• Found in the kidney for urine production.

Vein Characteristics

• Have a much larger lumen compared to arteries.
• Thinner tunica media.
• Blood drains out of capillaries into veins continuously, without a pulse.
• Contain far less elastin and smooth muscle compared to arteries.
• Flexible and contain pocket valves to prevent backflow.
• Blood flow is assisted by gravity and adjacent tissues/muscle contractions.
• The average adult has 4-6 liters of blood.

Plasma Composition

• 55% of blood volume.
• Liquid matrix in which cells are suspended.
• 90% water
• pH 7.4
• Contains electrolytes to maintain osmotic balance.
• Contains plasma proteins for clotting and buffers.
• Contains escorts for lipids.

Red Blood Cells

• Known as erythrocytes.
• 99.8% of cells in blood.
• Biconcave shape increases the surface area to volume ratio.
• Transport oxygen using hemoglobin to bind oxygen.

White Blood Cells

• Larger than red blood cells.
• Phagocytes engulf foreign materials.
• Lymphocytes produce antibodies.
• Used for defense.

Platelets

• Cell fragments that aid in clotting.

Tissue Fluid Dynamics

• Exchange of substances between tissue fluid and cells involves glucose via sodium-glucose co-transportation.
• Amino acids move by active transport.
• Oxygen and carbon dioxide move by diffusion.
• Approximately 85% of tissue fluid released by capillaries goes back to the capillaries.
• Excess tissue fluid drains into lymph ducts to prevent edema and becomes lymph.
• Lymphatic vessels merge with subclavian veins.

Heart Functions

• Collects blood in atria and pumps blood out of ventricles.
• Valves prevent backflow of blood.
• Consists mostly of cardiac muscle.
• Thicker on the left side because it pumps blood to the entire body.

Atria Characteristics

• Thinner muscular walls.
• Pump blood to ventricles to ensure full ventricles and empty atria.

Ventricle Characteristics

• Strong muscular walls generate high pressure to pump blood out to arteries.

Heart Valves

• Atrioventricular (A.V.) valves close to prevent backflow when ventricles contract.
• Open to allow flow when ventricles relax.
• Semilunar valves close to prevent backflow when ventricles relax.
• Open to allow flow when ventricles contract.

Cardiac Muscle

• Myogenic, contracting without a signal from the nervous system.
• Branched cells with connections between adjacent plasma membranes.
• Electrical signals propagate throughout the heart wall.
• Respond and are efficient.

Sinoatrial (S.A.) Node

• Pacemaker of the heart.
• Initiates a rhythm and coordinates contractions.
• Cells have few proteins but extensive membranes.
• First to depolarize in each cardiac cycle.

Atrioventricular (AV) Node

• Relay point that delays the impulse so the atria empties before the ventricles contract.

Septum

• Prevents oxygenated blood on the left from mixing with deoxygenated blood on the right.

Aorta

• Largest artery rising from the heart.

Coronary Arteries

• Carry oxygen and glucose from the aorta to the heart wall.

Coronary Veins

• Carry carbon dioxide from the heart wall to the right atrium.

Xylem Role

• Used in plants to transport water.
• Water evaporates from stomata.
• Water adheres to cellulose in the xylem.
• Cohesion between water molecules leads to transpiration pull from the root.
• This is a passive process.

Xylem Adaptations

• Column of cells end to end form continuous tubes.
• No membranes or organelles.
• When mature, xylem cells are dead.
• Walls are thickened with lignin to withstand great pressures.

Plant Stem Anatomy

• Epidermis provides waterproofing and protection.
• Cortex provides support and photosynthesis.
• Pith bulks out the stem.
• Phloem transports sugars from leaves to roots (or vice versa).
• Xylem transports water from roots to leaves.
• Cambium produces more xylem and phloem.

Plant Root Anatomy

• Epidermis absorbs water using root hairs.
• Endodermis is the inner layer through which water must pass to reach the xylem.

Coronary Artery Occlusion

• Coronary arteries can become partially or completely blocked by fatty deposits called atheroma (plaque).
• Restriction of blood flow causes pain (angina) and shortness of breath.
• Calcium deposits can develop, and a rough surface can trigger blood clots.
• Restriction of oxygen causes a heart attack.

Coronary Heart Disease (CHD) Risk Factors

• Hypertension
• Smoking/Vaping
• Obesity
• Saturated fats/cholesterol
• Excessive salt
• Alcohol
• Sedentary lifestyle
• Genetic predisposition
• Old age
• Diabetes

Diabetes

• High blood glucose levels.
• Can lead to increased glucose in urine, tissue damage, and impacts water reabsorption in kidneys, leading to more water in urine.
• Symptoms include frequent urination, constant thirst, fatigue, and sugary drink cravings.

Type 1 Diabetes

• Insulin dependent/early onset.
• Auto-immune disorder where the immune system destroys beta-cells.
• Accounts for 10% of diabetics.
• Treatment involves insulin injections.

Type 2 Diabetes

• Non-insulin dependent.
• Failure of target cells to respond normally to insulin.
• Can have genetic components but is not solely genetic.
• Sugary/fatty diets increase risk.
• Accounts for 90% of diabetics.
• Treatment involves diet/exercise, sometimes requiring medication.
• Diet should consist of small, high-fiber meals.

Bionic Pancreas

• Tracks glucose levels continuously and automatically delivers insulin.

Homeostasis Definition

• Maintenance of a constant internal environment of an organism.
• Keeps temperature, pH, blood glucose levels, and blood osmotic concentration stable.
• Involves monitoring levels of a variable and correcting changes by feedback loops.

Feedback Loops

• Information about the outcome of a process is used to either amplify or inhibit that process.
• Positive feedback increases the gap between the original set point and new level.
• Negative feedback decreases the gap, so the original level is restored.
• Requires vast amounts of energy.
• Can involve the nervous system and/or endocrine system.

Thermoregulation

• Birds and mammals use both physiological and behavioral changes to regulate body temperature.
• Body temperature is monitored by thermoreceptors (free nerve endings of specialized sensory neurons).
• Cold receptors are stimulated by low temperatures.
• Warm receptors are stimulated by high temperatures.
• Peripheral receptors are in the skin and influenced by external temperatures.
• Central receptors are in the core of the body, including the hypothalamus.

Responses to Heat

• Vasodilation widens the lumen, increases blood flow to skin, and increases heat loss.
• Sweating cools the blood flowing through the skin as the sweat evaporates.

Responses to Cold

• Vasoconstriction narrows the lumen, reduces blood flow to skin, and reduces heat loss.
• Shivering generates heat through small, rapid muscle contractions.
• Hair erection (goose-bumps) traps air to insulate, though ineffectual in humans.
• Uncoupled respiration in brown adipose tissue generates heat, not ATP, especially important in babies.
• When body temperature drops, thyroxine increases the metabolic rate of cells, releasing heat.

Thyroxine

• Lack of thyroxine can cause depression and could even be deadly in children.
• Main targets are liver, muscle, and brain cells.

Blood Glucose Regulation

• Islets of Langerhans in the pancreas contain alpha and beta cells.
• Alpha cells produce glucagon when low blood glucose levels are detected.
• Glucagon causes glycogen in the liver to be converted to glucose.
• As blood glucose levels increase, the production of glucagon decreases.
• Beta cells produce insulin when high blood glucose levels are detected.
• Insulin stimulates the uptake of glucose, and muscles store glucose as glycogen.
• Set point for glucose is about 5 mmol/L.

Explore the functions of blood, capillaries, and transport mechanisms in the body. This includes understanding the role of plasma proteins, red blood cells and arterial structures. Learn about the transport of amino acids and glucose.