Understanding the Circulatory System

The Circulatory System

• The circulatory system transports blood to deliver oxygen and vital nutrients to body cells
• It eliminates waste products
• It transports chemical messengers
• It helps maintain a constant body temperature
• Constant fresh blood flow is critical for cell and body survival

Components of the Circulatory System

• The heart acts as a pump
• Vessels (arteries, capillaries, and veins) carry fluid
• Blood is the fluid

Components of Blood

• Plasma includes 90% water, 10% dissolved salts, proteins, hormones, nutrients, waste products, and gases
• Red blood cells (erythrocytes) are the most abundant cells
  • They are manufactured in bone marrow and stored in the spleen
  • They carry oxygen
  • They lack nuclei or mitochondria
  • Red blood cells contain hemoglobin which has iron
  • They have a biconcave flexible shape
  • Iron gives blood its red color when exposed to oxygen
  • Iron is recycled in bone marrow and incorporated into new blood cells when the cell is destroyed
  • Oxygenated blood has oxygen bound to hemoglobin
  • Deoxygenated blood has given its oxygen to other cells
• White blood cells (leukocytes) are irregular in shape and made in bone marrow
  • They help fight infection by destroying and consuming bacteria and damaged cells
  • Pus mainly contains living and dead white blood cells with dead bacteria
  • A high white blood cell count indicates infection
• Platelets are cell fragments from special cells in bone marrow and help clot blood
  • Platelets break open and release chemical clotting factors into blood when damaged blood vessels are encountered
  • Factors help platelets stick together to form a plug
  • Biochemical reactions then take place to form strand-like molecules called fibrin
  • Fibrin forms a scaffold (a clot) so damage can be repaired
  • A scab contains blood cells, platelets, and fibrin

Separating Blood Components

• A centrifuge spun by density separates blood into its components
• Plasma makes up 55% of whole blood
• Leukocytes and platelets make up less than 1% of whole blood
• Erythrocytes makes up 45% of whole blood

The Process of Digestion

• Digestion is the physical and chemical breakdown of larger food particles into smaller ones
• Essential nutrients can then be absorbed into the bloodstream and lymph
• The gastrointestinal tract is the tube extending from the mouth to the anus where digestion occurs

Digestion in the Mouth

• Digestion begins physically through chewing and chemically through saliva secretion
• Enzymes are chemicals, proteins, produced by cells that speed up chemical reactions
• Saliva contains amylase, an enzyme that breaks down starch into smaller disaccharides which is chemical digestion
• Mucus dissolves and lubricates food to aid in swallowing

Swallowing

• Food is pushed from the mouth into the pharynx
• The larynx moves up, covering the glottis with the epiglottis, preventing food from entering the trachea
• Through involuntary smooth muscle contractions of the esophagus, peristalsis, food is pushed down through the esophagus and then into the stomach

Digestion in the Stomach

• Food enters from the esophagus via the gastroesophageal sphincter
• A sphincter is a circular muscle that contracts to close an opening in the body
• The stomach is a large J-shaped, four-layered section of the GI tract that physically and chemically breaks down food
  • Physical digestion occurs as muscles in the stomach contract to mix food with gastric juices to produce chyme which is semi-liquified
  • Chemical digestion occurs as nerves in the stomach detect when food is present and initiate the release of gastrin, a hormone that stimulates the release of hydrochloric acid and pepsinogen
• Gastric juice contains mostly mucus to protect stomach lining, hydrochloric acid (HCl), and pepsinogen
  • HCL lowers the pH value which activates pepsinogen, converting it into pepsin
  • Pepsin is an enzyme responsible for breaking down proteins
• Food can then enter the small intestine via the pyloric sphincter

Digestion in the Small Intestines

• The small intestines are small in diameter but long in length (7 m)
• The large intestine has a large diameter, but is only 1.5 m in length
• The small intestines are divided into three sections: the duodenum, the jejunum and the ileum
• The majority of nutrients are absorbed in the ileum

Structure of the Small Intestine

• The inner layer is folded to maximize surface area for nutrient absorption
• Within each fold are finger-like projections called villi, and microvilli
• Each villus contains a network of capillaries for absorption of carbs and proteins
• Fats are absorbed via lacteals

The Pancreas

• The pancreas is a long, flat gland in between the stomach and duodenum
• Digestive enzymes are secreted by the pancreas via the pancreatic duct and act on chyme that is expelled into the duodenum from the stomach

Digestive Secretions of the Duodenum and Pancreas

• Amylase continues digestion of starch
• Cholecystokinin (CCK) is secreted by the duodenum, and signals the pancreas to secrete various digestive enzymes.
• Secretin is secreted by the duodenum, and signals the pancreas to secrete bicarbonate ions (HCO3-) to neutralize acidic chyme and inactivates pepsin.
• Trypsinogen is produced by the pancreas
  • Once in the duodenum, it’s converted into trypsin by another enzyme called enterokinase
  • Trypsin breaks down any partially digested proteins into amino acids
• Lipases: Enzymes produced by the pancreas to break down lipids

The Liver and Gall Bladder

• The liver's main digestive function is to produce bile
• Bile is a substance that emulsifies fats into tiny droplets called micelles
  • This provides a greater surface area for lipases to act on
• Bile is continuously produced by the liver, but bile is stored in the gall bladder and excreted via the bile duct
• Before the blood from the intestines enters the systemic circuit, it passes through the liver where many toxins are removed, and nutrients are produced and stored

Absorption in the Large Intestines

• Food from the ileum makes its way to the cecum via the ileocecal valve
• Water, vitamins B, K and Na⁺ and Cl- are absorbed in the large intestine

Parts of the Large Intestine

• Cecum is a blind pouch at the upper end and contains the appendix
• Ascending colon and Transverse colon and Descending colon
• Rectum is where feces is stored
• Anus is an opening where feces are eliminated

The Mechanism of Egestion

• Nerves in the walls of the large intestine detect fecal movement into the rectum, initiating the 'defecation reflex'
• The external anal sphincter is made of skeletal muscle and can be controlled to hold in feces if necessary

Heart Rhythm

• The sinoatrial (SA) node, located in the right atrium, is the pacemaker
  • It generates an electrical signal to maintain heart rhythm
  • The SA node ‘leaks’ ions into the cells, starting depolarization, allowing cardiac muscle cells to contract without nerve stimuli
  • The electrical signals pass over the atria in a wave, causing the atria to contract
  • Then the signals reach a second mass of cells called the atrioventricular (AV) node
• The atrioventricular (AV) node in the lower right atrium delays and transmits signals from the SA node to the ventricles
  • Allows enough time for the atria to fully contract before ventricular contraction
• The Bundle of His receives the electrical signal from the AV node
  • It transmits it through the right and left bundle branches, running down the septum
  • Conducting fibers relay the signal to the Purkinje fibers, which spread throughout the ventricular walls
  • The electrical signal then triggers the ventricles to contract

Electrical Flow Through the Heart

• At rest, cardiac muscle cell membranes are polarized with more positive ions (mainly Na⁺ and Ca²⁺) outside than inside
  • This imbalance creates a negative resting membrane potential (around -80 to -90 mV)
• Ions move along the concentration gradient which is from high to low
• When charges balance out, it’s called depolarization
• The flow of charges (ions) generates an electric current in the heart, triggering contraction
• The 'leaky' SA node cells slowly depolarize to –40 mV, the threshold potential
  • At -40mV, the ion channels open, resulting in rapid depolarization
• As the SA node cells depolarize, positive ions (like Na⁺ and Ca²⁺) rapidly spread into neighboring atrial cells, causing their membrane potential to rise to threshold, then depolarize

Electrocardiogram (ECG or EKG)

• The flow of current can be detected using an electrocardiogram
• P wave: Atrial depolarization occurs as ions flow into the atrial cells which leads to depolarization
  • The electrical signal spreads from the SA node through the atria to the AV node, initiating atrial contraction
• QRS complex: Ventricular depolarization occurs as ions flow into the ventricular cells
  • The electrical signal moves from the AV node through the Bundle of His, the left and right bundle branches, and the Purkinje fibers to the ventricles initiating ventricular contraction
• T wave: Ventricular repolarization occurs as ions exit the ventricular cells, restoring the negative resting potential and preparing the heart for the next cycle
  • Represents the recovery phase of electrical activity in the ventricles

The Heart Cycle

• The heart cycle is a complete heartbeat of contraction and relaxation, taking ≈0.8s, and happens in two stages
• Systole is when the tricuspid and bicuspid valves close, ventricles contract, and blood is expelled into the arteries
  • Blood pressure is high at around 120 mm Hg
• Diastole is when the tricuspid and bicuspid valves open, ventricles relax and blood fills heart chambers
  • Blood pressure is low ≈80 mm Hg
• Blood pressure is measured using a sphygmomanometer and stethoscope

Heart Sounds

• “Lub” occurs when ventricles contract and atrioventricular valves snap shut
• “Dub” occurs when ventricles relax and semilunar valves snap shut
• A heart murmur (faulty heart valves) would not produce a clear ‘lub-dub’ sound

Cardiac Output

• Heart rate equals the number of heart beats per minute
• Stroke volume equals the volume of blood pumped by the left ventricle during each contraction
• Cardiac output equals the volume of blood pumped by the left ventricle per minute
• Cardiac output depends on stroke volume and heart rate and varies with activity level and fitness

Components of the Heart

• The heart has four chambers
  • Right atria and ventricles
  • Left atria and ventricles
  • Right and left side is separated by a muscular septum
• The right side receives deoxygenated blood while the left side receives oxygenated blood
• Valves direct blood flow

Tissues in the Heart

• Endocardium, epithelial tissue, lines chambers
• Myocardium, cardiac muscle, makes up the walls
• Pacemaker cells control heartbeat
• Nervous tissue responds to stimuli to increase or decrease heart rate
• Pericardium, connective tissue, encases the heart

Path of Blood Flow

• Blood flows through the pulmonary circuit: heart to lungs to heart
  • This is a low-pressure system
  • Deoxygenated blood picks up oxygen in the lungs
• Blood flows through the systemic circuit: heart to body to heart
  • This is a high-pressure system
  • Oxygenated blood from lungs gets delivered to body cells
• The coronary circulation delivers oxygenated blood to the heart muscle
  • The left coronary artery branches into left circumflex artery and left anterior descending artery

Blood Vessel Components

• Arteries carry blood away from the heart
  • They are thick-walled and elastic to resist high blood pressure
  • Inner wall contains epithelial cells, middle layer contains smooth muscle, outer layer contains connective tissue with elastic fibers
  • Arteries act like a rubber band to help propel blood to all body parts
• Arterioles branch from arteries with with smaller diameters, and are less elastic
• Capillaries are the narrowest vessels for gas exchange between blood and cells
  • Blood moves through cell by cell
  • They have a branching network that reaches all cells
• Veins carry blood towards the heart
  • Capillaries merge into venules, which merge into veins
  • Thin-walled, with large diameter and less muscular than arteries
  • Contain valves and skeletal muscle to help move blood back to heart (low pressure, against gravity)

Circulatory System Disorders

• Varicose Veins has veins near skin become dilated and knotted due to faulty valves and weakened vein walls causing backflow
  • Caused by prolonged standing, pregnancy, and heredity
  • Haemorrhoids are a varicose vein in the anal area
• Shock is when there is not enough blood to fill blood vessels which could be caused by haemorrhage, burn, nervous disturbance etc.
  • Not enough oxygen reaches the cells because blood pressure drops, so pulse rate increases and the person may pass out
  • Patients lie down with feet elevated and kept warm
• Anemia is when blood has too few red blood cells or not enough haemoglobin to carry oxygen
  • May cause fatigue, shortness of breath, paleness and rapid heart beat
  • Medication or a high iron diet helps
• Haemorrhage is an excessive loss of blood from an external wound or from an internal injury
  • Lowers blood pressure and causes shock
• Septal defect is when there is a hole between left and right atrium that mixes deoxygenated and oxygenated blood
  • Results in person easily becoming tired
  • If the hole is large, requires surgery
• Aneurysm is a blood-filled sac formed by the ballooning of an arterial wall that can occur in the brain or aorta
  • If it ruptures it is fatal because it results in huge blood loss, so it requires surgical removal
• Edema is when excess fluid accumulates causing swelling because lymph vessels similar to veins may not close properly
• Haemophilia is when people lack proper blood clotting proteins and bleed excessively, requiring synthetic proteins via injection
• Leukemia is a cancerous disease that damages white blood cells. causing them divide out of control and increase in numbers so the body can no longer properly fight off infections
• Angina is pain in heart muscle due to lack of oxygen; Dilating blood vessels can be treated with nitroglycerin
• Plaque is a sticky yellow substance composed of fatty deposits, calcium, etc, that is built up on the inside of arteries
• Arteriosclerosis is a group of disorders that cause the walls of blood vessels to thicken, harden and lose elasticity
• Atherosclerosis is a degeneration of the arteries cause by accumulation of plaque along the inner wall.
• Myocardial infarction/ Heart attack is the death of muscle tissue from blocked arteries
  • Muscle cells don’t receive enough oxygen and start to die, heart beat fails or stops
  • Symptoms: chest pain, shortness of breath, upper body pain, sweatiness and dizziness
• Stroke is a blockage of blood flow in the brain due to clogged arteries or brain haemorrhage, often causing brain damage
  • Symptoms: weakness, difficulty speaking and vision problems, headache and dizziness

Nutrients

• There are six essential nutrients to stay healthy: carbohydrates, lipids, proteins, water, minerals and vitamins
• Even at rest, cells need energy to stay alive
• Endothermic, warm blooded, organisms need more energy than ectothermic and cold blooded organisms, needing more food

Metabolism

• Metabolism refers to the set of chemical reactions that occur in an organism to stay alive
• Metabolism is a combination of catabolism and anabolism
• Catabolism is when reactions break down larger molecules into smaller ones, for example, the chemical and physical breakdown of nutrients in digestion
• Anabolism is when reactions produce larger molecules from smaller ones to build proteins for growth and repair
• Metabolic rate is the rate at which the body converts stored energy into useable energy, depending on: size, activity, sex, age and genetics
• Basal metabolic rate (BMR) is the minimum amount of energy that you need to stay alive

Carbohydrates

• Carbohydrates include sugars and starches
  • Examples: sugar, potatoes, rice, bread, pasta
• There are three types:
  • Monosaccharides are the simplest, also known as a simple sugar. Used directly by our cells to release energy, and taste sweet. Example glucose with the formula: C6H12O6
  • Disaccharides are two monosaccharide molecules bonded together. Example sucrose with the formula C12H22O11, also known as white table sugar
  • Polysaccharides are complex macromolecules made of hundreds or thousands of sugar molecules
    • Glycogen is a polymer of glucose, a storage carb in animal cells, mostly found in tissue in the muscle and liver
    • Starch is a storage carb found in plants and in starchy dishes
    • Cellulose is a polymer of glucose
      • Gives strength and structure to plant cells, but it is not digested by humans; also known as fiber

Protein

• Proteins are polymers of amino acids and have a variety of functions, for example controlling substances that enter and exit the cell, blood clotting, energy, and hair growth
  • Examples are hormones, enzymes, and membrane channel proteins
• Amino acids are the basic unit of a protein in which there are 20 different types; 12 are made by the body and 8 are obtained from food
• Amino acids combine to form many types of proteins
  • These are often called polypeptides
• Food high in protein includes meat, fish, dairy, beans, and tofu

Lipids

• Lipids are long-term energy storage molecules which include fats, oils, steroids and waxes
• Triglycerides are fats and oils composed of 3 fatty acids bonded to a glycerol molecule
  • Saturated fatty acids are molecules containing only single bonds between carbon and hydrogen
    • They come from animals and appear as solid at room temperature
    • Commonly linked to heart disease.
    • Examples include bacon fat and butter
  • Unsaturated fatty acids are molecules with one or more double bonds between carbon atoms from plants form and appear as liquid with examples like olive oil and canola oil.
    • They still can cause weight gain, but are less associated with health issues
• Phospholipids are a type of lipid with two fatty acids and a phosphate group that bond to a glycerol molecule. Examples are cell membranes
• Steroids contain four interconnected carbon rings that influence cellular activities like cholesterol, testosterone and estrogen.

Non-Energy Nutrients

• Water is required by the body for bodily processes, acting as a reactant for chemical reactions that take place in cells.
• Vitamins include organic molecules containing Carbon required by the body in small amounts
  • Regulate cell functions, growth and development for example,
    • Fat soluble vitamins, like Vitamins A, D, E and K that store and build up fat in the body
    • Water soluble vitamins, like Vitamins B and C that do not hold storage capabilities and excess amount is excreted through urine
• Minerals are elements that the body needs in small quantities
  • Used by metabolic activities and aids in building and repairing tissues like calcium and phosphorous.

Respiration

• Animals and plants both depend on oxygen for survival, drawing from food sources to energize their cells; This processes of obtaining energy in the cells is called cellular respiration
  • Aerobic cellular respiration basic chemical formula: C6H12O6 + 6O2 = 6CO2 + 6H20 + energy
  • From this reaction, the reactants originate from ingested nutrition, and photosynthesis
  • This process produces CO2 that evacuates when breathing occurs and water, that releases through perspiration, is called thermal waste to regulate body temperature ATP is an important element for cells because it has the important task of powering almost every energy-consuming requirement like forming movement, growing, and creating molecules

Differences in Aerobic Respiration

• Gas exchange is a term for the process where cells in the body acquire oxygen while also allowing out gases like carbon dioxide; where ventilation allows oxygen-rich air moving into lungs and letting carbon dioxide enriched air being carried away; All series of metabolic and chemical reaction that allow consumption of O2 to give energy to food tissues are known as Aerobic Cellular Respirtation

Human Respiratory System Structual Features

• A thin membrane allowing diffusion to occur,
• Surface level for gas exchange
• Healthy blood supply
• Respiration structures that move air that has oxygen to respiratory linings

Functionality

• Primary role: moving fresh air into the body while simultaneously extracting any waste material
• The nasal passages have natural safety functions which trap air particles using hair and mucus for defense against harmful foreign elements. The walls of the trachea also have their own linings with mucus-producing cells, in addition to other linings that specifically protect our lungs

Alveoli

• Alveoli act as ideal gas transfer structures considering that the membrane is already at one-cell thickness; the respiratory layers will transfer with ease considering that only has small distances between the lung and blood cells
• Respiratory structures that contribute in moving the air to other lung components are:
  • Nasal and oral cavities; responsible for bringing the air that passes through the mouth to the lungs
  • Pharynx aids in transfer that air and also supports digestive functions
  • Larynx keeps lung systems from taking in food
  • Trachea takes the air that will reach to different regions of the lungs and exhaling CO2
  • Epiglottis allows the air to reach to the larynx -Lungs that allows oxygen to come into the body
  • Bronchioles brings the air from small pockets called alveoli
  • Alveoli permits oxygen and carbon dioxide to pass into air sacs during breathing
  • Diaphragm functions by pulling the air into the lungs, causing a vacuum to engage -Pleural membranes help produce secretions that ensure free lung mobility
  • External intercostal Muscle aids in enlarging the rib cage for air flow for bringing O2 to the lungs -Internal Intercostal muscle forces the ribcage in a downwards motion

Exhalation Chart

• Negative air is pressured into the chest area in which the diaphragm shifts to cause air to enter the chamber; By the chamber, the atmosphere is moved as it flows around the area nearest to the nasal region
• Air that exists goes as negative when the diaphragm contracts in downward thrusts
• Air that exists goes as negative when the diaphragm contracts in downward thrusts

Lung Pressure

• The maximum Air which they can breath the lung for inhaling (Total Lung Capacity) and volume from an everyday inhale is the (Tidal Volume); The (Inspiratory & Expiratory Reserve Volume) regulates volume for inhalation by either breathing forcefully and the (Residual Volume) amount of the lungs after taking deep exhalations; (The Vital Capacity) regulates every amount when exhaling and taking deep intakes for breathing

Air Transfer

• Higher Elevation causes little increase as air elements have no density than levels by the sea;
• During physical fitness training at levels to increase red tissues as the body will give to increase tissue that is oxygen to the levels during ability; the breathing movement is a constant flow that is regulated using signals within the brain where movement the body can relax by the diaphragm and the center within the brain.