Respiratory and Digestive System Test
Here’s a breakdown of each topic, simplified for easier understanding.
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### How We Breathe
Breathing, or respiration, happens because of changes in air pressure inside our chest. When we inhale, our diaphragm and intercostal muscles (muscles between ribs) contract. This makes the chest cavity larger, creating lower pressure inside our lungs than outside. Air flows in to fill the space. When we exhale, these muscles relax, making the chest cavity smaller and pushing air out.
### Starting Points for Digesting Nutrients
- Carbohydrates: Digestion starts in the mouth with an enzyme called amylase in saliva, which begins breaking down starches.
- Proteins: Digestion begins in the stomach, where the enzyme pepsin starts to break down proteins.
- Lipids (Fats): Digestion starts in the small intestine with help from bile (from the liver) and enzymes from the pancreas.
### Roles of Digestive Organs and Accessory Organs
- Mouth: Chews food (mechanical digestion) and starts breaking down carbs with saliva.
- Esophagus: Moves food from mouth to stomach via peristalsis (wave-like muscle contractions).
- Stomach: Mixes food and secretes acid and enzymes to digest proteins. Turns food into a liquid called chyme.
- Small Intestine: Main site for nutrient absorption. Enzymes from the pancreas and bile from the liver help digest food further.
- Large Intestine: Absorbs water and electrolytes, forming solid waste (feces).
- Liver: Produces bile, which helps digest fats.
- Pancreas: Releases digestive enzymes and bicarbonate to neutralize stomach acid in the small intestine.
- Gallbladder: Stores bile from the liver until it’s needed for fat digestion.
### Important Vocab
- Peristalsis: Muscle movements that push food through the digestive system.
- Chyme: Semi-liquid food mixture that leaves the stomach.
- Bile: A fluid produced by the liver that helps digest fats.
- Alveoli: Tiny air sacs in the lungs where gas exchange happens.
- Diaphragm: Main muscle involved in breathing.
### Breathing Muscles and Their Roles
- Diaphragm: Contracts to enlarge the chest cavity during inhalation.
- Intercostal Muscles: Help expand and contract the ribcage.
- Accessory Muscles (in neck and chest): Help with deep breathing or labored breathing.
### Gas Laws and Breathing
Boyle's Law explains breathing: when the volume of a space increases, pressure decreases, and vice versa. This is why air flows into the lungs when the chest expands (lower pressure) and out when the chest contracts (higher pressure).
### How Gas Exchange Occurs
Gas exchange happens in the alveoli, where oxygen moves from the air into the blood, and CO₂ moves from the blood to be exhaled. This is driven by partial pressure gradients: oxygen moves where there’s less oxygen, and CO₂ moves where there’s less CO₂.
### Chemical vs. Physical Digestion
- Physical (Mechanical) Digestion: Breaking food into smaller pieces without changing its chemical structure (e.g., chewing, stomach churning).
- Chemical Digestion: Breaking down food into simpler molecules with enzymes (e.g., proteins into amino acids, carbs into sugars).
### What Happens to Food Through the GI Tract
- Mouth: Chews and mixes food with saliva.
- Esophagus: Moves food to the stomach.
- Stomach: Secretes acid and enzymes to break down proteins.
- Small Intestine: Digests food with enzymes and bile; absorbs nutrients.
- Large Intestine: Absorbs water, forms feces, and hosts beneficial bacteria.
### Role of Carbohydrates in Nutrition
Carbohydrates are a primary energy source for the body. They’re broken down into glucose, which cells use to produce energy in a process called cellular respiration.
### Cellular Respiration - Produces Energy
Cellular respiration is the process that breaks down glucose to release energy in the form of ATP (the cell’s energy currency). It involves three main stages:
- Glycolysis: Happens in the cytoplasm; glucose is split into pyruvate, producing a small amount of ATP.
- Krebs Cycle: Takes place in the mitochondria; breaks down pyruvate into CO₂, releasing energy carriers.
- Electron Transport Chain (ETC): Also in mitochondria; uses energy carriers to produce most ATP, with oxygen as the final electron acceptor, producing water.
### Types of Nutrients
- Carbohydrates: Main energy source (sugars and starches).
- Proteins: Build and repair body tissues.
- Lipids (Fats): Energy storage, insulation, and cell structure.
- Vitamins and Minerals: Support various body functions (e.g., immune system, bone health).
### Summary of Cellular Respiration Stages
1. Glycolysis: Starts with glucose, produces ATP and pyruvate.
2. Krebs Cycle: Starts with pyruvate, releases CO₂, and produces energy carriers.
3. Electron Transport Chain: Uses energy carriers to produce ATP and water.
### Glycolysis
Glycolysis is a ten-step process that splits glucose into two pyruvate molecules, producing a small amount of ATP and some energy carriers.