Circulatory System: Pulmonary vs. Systemic Circulation

Circulatory System: Pulmonary vs. Systemic Circulation

• Pulmonary arteries transport oxygen-poor blood to the lungs.
• Pulmonary veins transport oxygen-rich blood to the heart.
• Blood flows from the lungs to the left atrium, then the left ventricle, and finally the aorta, which distributes blood to the body.
• Capillaries facilitate the movement of oxygen and nutrients into cells, while carbon dioxide and waste move into the blood.
• Oxygen-poor blood returns through the superior vena cava (from the upper body) and the inferior vena cava (from the lower body).
• Blood flows from the right atrium to the right ventricle, then to the pulmonary arteries, reaching the lungs, and oxygenated blood returns to the left atrium via the pulmonary veins.

Full Blood Flow Pathway

• The complete blood flow pathway is: Superior/Inferior Vena Cava → Right Atrium → Tricuspid Valve → Right Ventricle → Pulmonary Valve → Pulmonary Arteries → Lungs (gas exchange) → Pulmonary Veins → Left Atrium → Bicuspid Valve → Left Ventricle → Aortic Valve → Aorta → Arterioles → Capillaries (gas exchange) → Venules → Veins → Vena Cava.

Heart's Own Blood Supply

• The heart gets its oxygen and nutrients from the coronary arteries, which branch off from the aorta and not from the blood inside it.

Regulation of the Heartbeat: Basics

• The heart beats approximately 100,000 times a day, at a rate of 60–100 bpm (beats per minute).
• Heartbeat is affected by factors such as age, fitness level, and emotional state.

Pacemaker: SA Node

• The sinoatrial (SA) node is located in the right atrium.
• The SA node sends electrical signals to stimulate heart muscle contraction.

Electrical Impulse Pathway

• The SA node initiates the impulse, causing both atria to contract.
• The atrioventricular (AV) node delays the impulse, allowing blood to fill the ventricles.
• The impulse travels to the Purkinje fibers, causing both ventricles to contract.

ECG Waves

• The P wave on an ECG indicates atrial contraction.
• The QRS wave indicates ventricular contraction.
• The T wave indicates ventricular relaxation.

Control of Heart Rate

• Intrinsic control means the heart beats on its own due to myogenic muscle.
• Extrinsic control involves the nervous system: sympathetic nerves increase heart rate, while parasympathetic nerves decrease it.
• Hormones like noradrenaline (from the brain) and adrenaline (from the adrenal glands) increase heart rate.

Measuring Blood Pressure

• A sphygmomanometer (pressure cuff) is used to measure blood pressure.
• Systolic pressure is the pressure when ventricles contract.
• Diastolic pressure is the pressure when ventricles relax.
• Normal blood pressure is 120/80 mmHg.

What Affects Blood Pressure

• Blood pressure depends on cardiac output (blood pumped per minute) and artery resistance (elasticity).
• Factors like height, weight, fitness, time of day, hydration, and activity level influence blood pressure.
• Smoking and a fatty diet cause stiff arteries, leading to high blood pressure.

Respiratory System: Why We Breathe

• Cellular respiration occurs in mitochondria, requiring oxygen and producing carbon dioxide.
• Gases move via diffusion.

Three Main Steps of Respiration

• Breathing
• Transport of gases
• Gas exchange in cells

Gas Exchange Surfaces

• Gas exchange surfaces must be thin, moist, large, and permeable to gases.

Gas Exchange in Terrestrial Animals

• Air contains more oxygen and is easier to move than water.
• Moisture loss is the primary challenge in terrestrial gas exchange.
• Internal surfaces (trachea, lungs) are used to reduce moisture loss.

Lungs

• Air enters the lungs where oxygen diffuses into the blood, and carbon dioxide diffuses out.
• Blood transports oxygen to body cells.

Human Respiratory System

• Air Pathway: Nose/Mouth → Pharynx → Larynx (voice box) → Trachea → Bronchi → Bronchioles → Alveoli (air sacs) → capillaries

Respiratory System: Structures

• The trachea is supported by cartilage rings.
• Alveoli are millions of tiny, moist sacs that provide a large surface area for gas exchange.

Respiratory System: Lining

• Epithelial tissue, with mucus and cilia, trap and remove particles.
• Mucus traps particles.
• Cilia sweeps particles toward the throat.

Breathing Process

• Inhalation involves the diaphragm and rib muscles contracting, which expands the chest, increases lung volume, decreases pressure, and allows air to flow in.
• Exhalation involves the muscles relaxing, which decreases lung volume, increases pressure, and forces air out.

Gas Exchange at Alveoli

• Oxygen dissolves in the moisture of the alveoli.
• Oxygen diffuses into capillaries and binds to hemoglobin.
• Oxygen creates a diffusion gradient (alveoli → blood).
• Carbon dioxide from cells diffuses in reverse: from blood → alveoli → exhaled.

Breathing Control

• Breathing is mostly involuntary, controlled by the medulla oblongata in the brain.
• The brain monitors carbon dioxide (CO2) levels.
• More CO2 leads to lower blood pH and faster breathing to remove CO2.

Cell Theory

• All living things are made of cells.
• Cells are the basic structural and functional units of life.
• All cells come from pre-existing cells.
• Eukaryotic cells have a nucleus (e.g., muscle cells).
• Prokaryotic cells lack a nucleus (e.g., most bacteria).

Levels of Organization

• Cells are the basic unit of life.

Tissues

• Tissues are similar cells with a common function.
• Epithelial tissue provides protection and lining.
• Connective tissue supports and binds (e.g., bone, fat, blood).
• Muscle tissue enables movement.
• Nervous tissue facilitates communication.

Organs and Systems

• Organs are groups of tissues (e.g., heart, stomach).
• An organ system consists of related organs working together.
• An organism is a complete living system of organs.

Homeostasis

• Homeostasis maintains stable internal conditions despite external changes.

Normal Range

• The body can tolerate small changes within a normal range.
• Conditions outside this range may indicate illness.

Negative Feedback

• Negative feedback is a system that reverses changes to return to normal.
• For example, high blood sugar stimulates insulin release, which lowers blood sugar.
• If the body temperature lowers to < 36.2°C, blood flow to the skin reduces, shivering starts, and the heart rate increases.
• If the body temperature increases to > 37.2°C, more blood flows to the skin, and sweating and muscle relaxation occur.

10.1 Nutrition & Digestion: Nutrients

• Nutrients are substances in food that support body functions.
• Macronutrients include carbs, proteins, fats, and water.
• Micronutrients include vitamins and minerals.

Food Processing

• Food processing involves breaking down large food molecules into smaller ones for energy and building.
• It also involves building new molecules to maintain cells.

Carbohydrates

• Carbohydrates are made of carbon, hydrogen, and oxygen.
• Carbohydrates are the main energy source (e.g., glucose).

Carbohydrates: Types

• Simple carbs include sugars (e.g., fruit, honey, milk).
• Complex carbs include starches (e.g., bread, rice, potatoes).
• Fibre (cellulose) aids digestion but is not broken down.

Proteins

• Proteins are made of 20 amino acids.
• Proteins are used for structure, messaging, and immune response.
• Enzymes are special proteins that speed up reactions.
• Nine essential amino acids must come from the diet, with sources like meat, milk, rice, and lentils.

Fats (Lipids)

• Fats are made from fatty acids and glycerol.
• Fats store energy and help absorb fat-soluble vitamins.

Fats (Lipids): Types

• Saturated fats come from animals (e.g., butter) and can clog arteries.
• Unsaturated fats come from plants and fish (e.g., olive oil) and are healthier.
• Trans fats are processed, unhealthy, and have a long shelf life.

Vitamins & Minerals

• Vitamins are organic and needed in small amounts.
  • Water-soluble vitamins (C, B) are not stored.
  • Fat-soluble vitamins (A, D, E, K) are stored.
• Minerals are inorganic (e.g., calcium, sodium).
• Probiotics are healthy bacteria.
• Antibiotics kill bacteria.

Digestive System: 4 Stages

• Ingestion is eating.
• Digestion:
  • Mechanical digestion is chewing.
  • Chemical digestion involves enzymes + water (hydrolysis).
• Absorption is the process of nutrients entering the blood (mostly in the small intestine).
• Elimination is the removal of undigested material (feces).

Digestive Tube (Alimentary Canal)

• The digestive tube is a long tube that goes from the mouth to the anus.
• Digestion and absorption occur here.

Organs of the Alimentary Canal: Mouth

• Mechanical digestion is carried out by the teeth and tongue.
• Saliva contains amylase, which breaks starch down to sugar.
• Mucus in saliva helps with swallowing.

Pharynx

• The bolus (chewed food) enters the throat.
• The epiglottis covers the trachea during swallowing.

Esophagus

• The bolus moves via peristalsis (muscle waves).
• The esophageal sphincter prevents stomach acid backflow, preventing heartburn.

Stomach

• The stomach is an elastic sac that holds about 2 liters.
• Chemical digestion involves gastric juice, which contains acid + enzymes (pepsin) + mucus, kills bacteria, and breaks down protein.
• Mechanical digestion involves churning food into chyme.
• The pyloric sphincter controls the flow into the small intestine.

Small Intestine (6m)

• The small intestine has three parts: duodenum, jejunum, and ileum.
• The duodenum is where digestion occurs with help from the liver and pancreas.
• Bile (from the liver, stored in the gallbladder) breaks up fat.
• Lipase (from the pancreas) digests fat.
• Pancreatic juice neutralizes acid and digests all nutrients.
• The jejunum and ileum are where nutrient absorption occurs.
  • Villi & microvilli increase the surface area.
  • Nutrients go to the liver for processing/detox.

Large Intestine (Colon)

• The large intestine is shorter but wider (1.5m x 5cm).
• The large intestine absorbs water from undigested food resulting in waste becoming feces.
• Bacteria produce vitamins (K, B).
• The rectum stores feces.
• The anus is controlled by two sphincters.

Diagnosing Digestive Disorders

• Common issues include:
  • Gas: swallowed air or bacteria digestion.
  • Diarrhea: not enough water absorbed.
  • Constipation: too much water absorbed.

Diagnostic Tools

• Endoscopy involves inserting a camera tube via the throat.
• Colonoscopy involves inserting a camera via the rectum.
• Biopsy involves taking a sample of tissue under a microscope.
• Pill camera is a less invasive internal view.