Blood Components and Functions

Lecture 1 - Blood

• Albumins are important for colloid osmotic pressure
• Fibrinogen crucial for blood clotting
• Nutrients include glucose, lipids, amino acids, hormones, and dissolved gases like oxygen and carbon dioxide

Functions of Formed Elements

• Red blood cells transport oxygen and carbon dioxide, bound to hemoglobin
• White blood cells perform immune functions
• Platelets and fibrinogen interact for coagulation or clotting

White Blood Cells

• Neutrophils are phagocytic cells and the most numerous white blood cells, making up 50-70% in circulation
• Eosinophils fight parasitic worm infections, are somewhat phagocytic, and rare
• Basophils participate in inflammation and allergic responses, and are rare
• Macrophages are phagocytic cells residing in tissues to detect and consume invaders
• Monocytes are immature macrophages
• Lymphocytes are common in circulation, accounting for 20-35%
• B-lymphocytes and T-lymphocytes produce antibodies in antibody-mediated immune responses

Blood production

• Adult production happens in red bone marrow located in the pelvis, spine, ribs, cranium, and proximal ends of long bones

Components of Hemoglobin

• Hemoglobin consists of four globular polypeptide (protein) chains composed of alpha and beta globulin
• Each chain contains a heme molecule with central iron, which binds with oxygen, CO2 binds to chains
• Each hemoglobin can bind four oxygen or four carbon dioxide molecules
• Bilirubin is a breakdown product of heme

Blood Clotting

• Blood clotting occurs in four steps

• Vasoconstriction occurs when a vessel is damaged, and exposed collagen and damaged endothelial cells release paracrine cells to stimulate vessel smooth muscle to spasm

• Exposed collagen binds to platelets, which release chemicals and activate more platelets to form a soft plug

• The coagulation cascade involves tissue factor released by damaged endothelium and exposed collagen, triggering a complex series of reactions

• Thrombin converts inactive fibrinogen into fibrin to form a hard clot.

Blood Cell Production and Stimulators

• Erythropoietin stimulates red blood cell production
• Colony Stimulating Factor stimulates white blood cell production
• Thrombopoietin stimulates platelet production

Carbon Monoxide Risks

• Carbon monoxide binds to hemoglobin 300x more strongly than oxygen
• Carbon monoxide exposure causes hypoxia due to oxygen's inability to bind

Lecture 2 - Ventilation Ⅰ

• The order of air passage for oxygen is nose, pharynx, epiglottis, larynx, trachea, bronchi, bronchioles, and alveoli air spaces
• The order of air passage for carbon dioxide is alveoli air spaces, bronchioles, bronchi, trachea, larynx, epiglottis, pharynx, and nose

Nasal Structures

• The vestibule, lined with skin containing coarse hairs filters air
• Mucus membranes with capillary beds warm and moisten air

Additional Respiratory Structures

• The pharynx is a passageway for both air and food, leading to the trachea and esophagus
• The epiglottis prevents food and water from entering the trachea
• The larynx contains the vocal cords

Respiratory Epithelium Characteristics

• Mucus captures dust and particles
• Mucus contains antibodies that destroy some pathogens
• The mucociliary escalator moves trapped particles
• Cilia sweep trapped particles toward the pharynx to be expectorated or swallowed

Bronchi and Bronchioles

• The right primary bronchus is shorter, wider, and more vertical, increasing the likelihood of aspirated objects entering the right lung
• Bronchioles are small, collapsible pathways with smooth muscle walls
• Bronchoconstriction is caused by increased PSNS
• Bronchodilation is caused by increased SNS

Alveolar Epithelium

• Type 1 alveolar cells make up 97% of the alveolar surface
• Type 2 alveolar cells secrete pulmonary surfactant
• Macrophages consume debris and foreign bodies
• Fibroblasts produce elastic fibers for alveoli stretch and recoil

Fick's Law and Alveoli

• Gas exchange is optimized by increased surface area, concentration gradient, permeability and a thin membrane

Vocal Cord Pitch

• Pitch depends on tension
• Elongated vocal cords (high tension) produce higher notes
• Shortened vocal cords (low tension) produce lower notes
• Testosterone thickens vocal cords during puberty, resulting in deeper tones

Lecture 3 - Ventilation Ⅱ

• Inhalation: the diaphragm contracts, increasing the thoracic cavity volume, creating a vacuum, and causing the lungs to expand. Alveolar volume increases, intra-alveolar pressure decreases, and air flows in
• Exhalation: the diaphragm relaxes, decreasing the thoracic cavity volume and causing the lungs to recoil. Alveolar volume decreases, intra-alveolar pressure increases, and air flows out

Lung Compliance

• Compliance is the ease of lung expansion during inhalation
• Compliance depends on pulmonary surfactant and elastic fibers

Pulmonary Surfactant

• Pulmonary surfactant is a lipid and protein fluid secreted by type 2 alveolar cells to reduce surface tension and prevent alveolar collapse

Elastance

• Elastance is the ease of the lungs recoiling back to their original shape during exhalation and depends on elastic fibers made by fibroblasts

Autonomic Nervous System Influence on Bronchioles

• Increased PSNS and decreased SNS cause smooth muscle contraction, leading to narrowed radius (bronchoconstriction), higher resistance, and reduced airflow
• Decreased PSNS and increased SNS cause less smooth muscle contraction, resulting in widened radius (bronchodilation), lower resistance, and increased airflow
• During fight or flight, epinephrine causes severe bronchodilation, further reducing resistance and increasing airflow

Lung Volumes

• Tidal Volume (TV) is the volume of air entering/leaving during a normal breath
• Pulmonary Ventilation is the volume of air moving in and out of the lungs per minute, which is calculated as TV x Respiratory Rate
• Inspiratory Reserve Volume (IRV) is the extra volume can be moved in during inspiration
• Expiratory Reserve Volume (ERV) is the extra volume can be moved out during expiration
• Vital Capacity (VC) is equals TV + IRV + ERV
• Residual Volume is the air remains in the lungs after exhaling
• Total Lung Capacity is equals VC (TV+IRV+ERV) + RV

Premature Babies

• Premature babies are more likely to experience collapsed lungs
• Alveoli can collapse with each breath due to lack of surfactant, which is produced in late gestation
• Surfactant is delivered via an endotracheal tube, and alveoli are kept partially inflated with CPAP or a ventilator

Lecture 4 - Gas Exchange

• Oxygen moves from the atmosphere to alveoli to blood to tissues
• Carbon dioxide moves from tissues to blood to alveoli to the atmosphere

Alveolar Exchange Factors

• Alveolar ventilation, which includes the rate and depth of breathing, is a factor; depression of central nervous system reduces the rate and depth
• Airway resistance impacts alveolar exchange where reduced radius of bronchioles or other passages increases airflow resistance
• Lung compliance impacts alveolar exchange and the inability of lungs to expand reduces the rate
• Gas diffusion is impacted by surface area and diffusion distance
• Decreased surface area decreases diffusion rate
• Increased membrane thickness reduces diffusion rate

Gas Transport in Blood

• Only 2% of oxygen is dissolved in plasma while 98% is bound to hemoglobin inside red blood cells
• 7% carbon dioxide is dissolved in plasma while 23% is bound to hemoglobin inside red blood cells, and 70% is converted to bicarbonate ion

Oxygen Affinity Factors

• Oxygen affinity is affected by pH, temperature, and CO2
• In working tissues, increased acidity, and temperature, or CO2 decreases oxygen binding affinity

Hypoxia and Hypercapnia

• Hypoxia is lower-than-normal oxygen in blood and tissues, with symptoms like rapid breathing, cyanosis, poor coordination, lethargy, and visual impairment
• Hypercapnia is a higher-than-normal level of carbon dioxide in tissues or blood, with symptoms like rapid breathing, flushed skin, altered consciousness, confusion, and sweating

Carbon Dioxide in Blood

• Most carbon dioxide is carried by hemoglobin or as bicarbonate ion rather than in plasma
• If more than 7% of carbon dioxide was in plasma, blood would bubble like soda

Lecture 5 - Kidney Ⅰ

• The kidney filters blood and produces urine
• Ureters transport urine via peristalsis to the urinary bladder
• The urethra is tube for urine to leave the bladder

Bladder

• The bladder is made of smooth muscle called detrusor muscle, innervated by PSNS autonomic motor efferent neurons

Sphincters

• The internal sphincter is a continuation of the detrusor muscle and involuntary
• The external sphincter is skeletal muscle and voluntary

Urinary Bladder Wall

• The urinary bladder has stretch sensitive neurons that signal the spinal cord as it fills and pressure increases

Micturition Steps

• Micturition: increased pressure and stretch stimulates stretch sensitive neurons in the bladder wall
• Afferent path: sends action potentials to the spinal cord, which acts as the integrator
• Efferent paths: Somatic motor neurons cease action potentials, and PSNS autonomic motor neurons send action potentials
• Effectors include the skeletal muscle of external sphincter relaxing and smooth muscle contraction as internal sphincter opens, with Micturition

Kidney Functions

• Blood osmolarity regulation
• Maintenance of specific ion concentrations
• Blood pH regulation via H+ and HCO3- secretion and excretion
• Excretion of wastes like creatine, urea, and urobilinogen
• Gluconeogenesis during stress/starvation through conversion of amino acids

Kidney Structures

• Cortical nephrons: 80% with a small portion of loop of Henle in medulla
• Juxtamedullary nephrons are 20% with a loop of Henle extending deep into the medulla for making urine more or less concentrated

Sequence of Blood Flow

• The blood flows through blood vessels in the order of the renal artery, afferent arteriole, glomerular capillaries (glomerulus), efferent arteriole, peritubular or vasa recta capillaries, renal venules, and renal vein

Sequence of Filtrate Flow

• The filtrate flows through the order of Bowman’s capsule, proximal tubule, loop of Henle, distal tubule, collecting duct, renal pelvis, ureter, bladder, to the urethra

Capillaries

• Peritubular capillaries surround the loop of Henle in cortical nephrons
• Vasa recta capillaries surround the loop of Henle in juxtamedullary nephrons

UTIs

• Women have a higher susceptibility to urinary tract infections because their shorter, straight urethra allows bacteria to travel more easily up the tract

Lecture 6 - Kidney Ⅱ

• The four processes of the nephron are filtration, reabsorption, secretion, and excretion

Nephron Processes

• During Filtration, water and substances (filtrate) are filtered into the nephron's tubular elements from glomerular capillary blood at the glomerulus
• During Reabsorption, some filtrate is moved from tubular elements back into blood
• During Secretion, the substances are transported from the peritubular/vasa recta capillary blood into the tubular elements of the nephron everywhere except the glomerulus and Loop of Henle
• During Excretion, what is left in the tubular elements is eliminated as urine

Glomerular Pressures

• Net filtration pressure is determined by glomerular capillary blood pressure(favors filtration), colloid osmotic pressure(opposes filtration) and Bowman’s capsule hydrostatic pressure(opposes filtration)
• Glomerular capillary blood pressure can change in a healthy person

Autoregulation

• Increased Afferent Radius leads to Increased Glomerular Capillary Blood Pressure and Net Filtration Pressure, resulting in Increased Glomerular Filtration Rate and Urine Volume
• Decreased Afferent Radius leads to Decreased Glomerular Capillary Blood Pressure and Net Filtration Pressure, resulting in Decreased Glomerular Filtration Rate and Urine Volume
• Decreased Efferent Radius leads to Increased Glomerular Capillary Blood Pressure and Increased Net Filtration Pressure, resulting in Increased Glomerular Filtration Rate and Urine Volume
• Increased Efferent Radius leads to Decreased Glomerular Capillary Blood Pressure and Decreased Net Filtration Pressure, resulting in Decreased Glomerular Filtration Rate and decreased urine volume

Responses to Mean Arterial Blood Pressure

• Decreased Mean Arterial Blood Pressure with Decreased Efferent Radius and Increased Afferent Radius leads to Increased Glomerular Capillary Blood Pressure and Net Filtration Pressure, resulting in Increased Glomerular Filtration Rate and Urine Volume
• Increased Mean Arterial Blood Pressure with Increased Efferent Radius and Decreased Afferent Radius leads to Decreased Glomerular Capillary Blood Pressure and Net Filtration Pressure, resulting in Decreased Glomerular Filtration Rate and Urine Volume

Myogenic Mechanism:

• Increased blood pressure (MAP) leads to an Increased stretch of afferent arteriole
• This will trigger the Stretch sensitive ions channels open, opening Ca2+ channels
• Ca2+ binding will cause smooth muscle contractions, constricting afferent arteriole
• This will trigger a Reduced blood flow into glomerular capillaries
• It will Decrease GFR

Autonomic Nervous System Autoregulation:

• Severe drop in blood pressure (severe shock, hemorrhage, or severe dehydration)
• Cause the Cardiovascular center in the medulla to severely increase SNS activity
• This leads to Systemic vasoconstriction, and both the afferent and efferent arterioles will constrict, decreasing GFR and urine production
• The goal is to keep all fluid in the plasma, restoring blood volume and blood pressure

Squatting

• Avoid squatting contests
• Rhabdomyolysis is EXTREME exertion during exercise damages muscle tissue, releasing myoglobin into the blood
• Myoglobin has damaging effects on kidney filtration and can cause kidney damage
• This can lead to kidney failure and death

Lecture 7 - Kidney Ⅲ

• Sodium is absorbed through secondary active transport with other molecules from the tubule lumen into tubule cells
• Sodium is transported both from tubule cells into extracellular fluid with the sodium potassium pump

Loop of Henle

• The descending loop has water channels for water reabsorption
• The ascending loop features Na+/K+/Cl- co-transporters, enabling ion reabsorption and helping attract water from the osmosis

Vasopressin

• Vasopressin acts on the end of the distal tubule and collecting duct.
• Vasopressin also inserts more aquaporins in the collecting duct to reabsorb more water generating more concentrated urine
• Less vasopressin results in less = water absorption, less concentrated urine

Aldosterone

• Aldosterone acts on the distal tubule.
• Aldosterone also increases sodium potassium pumps to increase Na+ reabsorption
• Increased levels of aldosterone result in high sodium reabsorption and high potassium excretion
• Decreased levels of aldosterone result in low sodium reabsorption and low potassium excreation

Acid-Base Balance

• Basic (alkalosis): the kidneys secrete bicarbonate (HCO3-) and reabsorb hydrogen (H+), and brings acid into the blood to balance pH
• Acidic (acidosis): the kidneys secrete hydrogen (H+) and reabsorb bicarbonate (HCO3-), and Brings base into the blood to balance pH

Mild Diuretic

• Caffeine makes people pee due to it being a mild diuretic