The Digestive System

• The digestive system consists of seven steps: ingestion, mechanical breakdown, chemical breakdown, swallowing, peristalsis, digestion in the stomach and small intestine, absorption in both intestines, egestion.

Mechanical and Chemical Breakdown

• Mechanical breakdown happens through the teeth.
• Chemical breakdown involves enzymes to break down food materials.
• Amylase is an enzyme that breaks down carbohydrates into glucose.

Peristalsis

• Peristalsis uses muscle contractions to propel food downwards to form a bolus.

Digestion in the Stomach

• Chemical digestion of proteins occurs using hydrochloric acid and pepsin to break proteins into amino acids forming gastric juices.
• Muscular contractions allows for mechanical digestion.

Digestion in the Small Intestine

• The small intestine consists of the duodenum, jejunum (absorption), and ileum (absorption).
• The duodenum connects to the liver and pancreas and receives bile (from the liver) and pancreatic juice (from the pancreas).
• The gallbladder stores bile that that breaks down fats.
• The liver produces bile to break down fats, neutralize stomach acid, and get rid of toxins.
• The pancreas produces protease (breaks down polypeptides into amino acids), lipase (breaks down lipids into glycerol and fatty acids), amylase, and pancreatic juices.

Absorption

• Absorption involves digested food substances, minerals and vitamins from the small intestine to be transported throughout the body.
• Intestinal walls are lined with villi to increase surface area for improved absorption of nutrients.
• Digested food is absorbed, then assimilated by the cells to be utilized.
• The large intestine allows for the final state of absorption of water, vitamins, and minerals.
• Undigested food materials are converted into waste product.

Egestion

• Feces are temporarily stored in the rectum, before emptying through the anus.

Components of the Digestive System

• The main components are the mouth (with tongue and salivary glands), esophagus, liver, bile duct, gallbladder, stomach, pancreas, small intestine, large intestine, rectum, and anus.

Breakdown of Food Molecules

• Proteins are broken down into amino acids by pepsin and protease to build other proteins.
• Carbohydrates are broken down into glucose by amylase for energy.
• Lipids (fats) are broken down into glycerol and fatty acids by lipase for energy and insulation.

Circulatory System

Components

• The circulatory system's three major components are blood, the heart, and blood vessels.

Functions

• Transports oxygen & CO2.
• Distributes nutrients & transports water.
• Maintains body temperature.
• Circulates hormones.

Types of Circulation

• Systemic circulation carries blood from the heart to the organs and tissues in the body, and back to the heart.
• Pulmonary circulation carries blood to and from the lungs.
• Blood moves from the lungs where it absorbs oxygen and releases CO2 before returning to the heart

Heart Beats and Blood Pressure

• Normal blood pressure is 120/80.
• Low blood pressure reduces the capacity to transport blood.
• High blood pressure can weaken arteries, which can result in rupture.
• Diastole is when the heart relaxes (80).
• Systole is when the heart contracts (120).

Cardiac Cycle

• Cardiac diastole occurs when all chambers are relaxed & blood flows into the heart.
• Atrial systole consists of the atria contracting, pushing blood into ventricles.
• Ventricular systole occurs after atria relax, ventricles contract, pushing blood out of heart.

Components of Blood

• Plasma is the fluid component composed of 90% water, and 10% proteins.
• Red blood cells (erythrocytes) are responsible for oxygen & CO2 binding.
• They’re red because of the protein hemoglobin, contains iron which binds oxygen to it.
• Hemoglobin is a polypeptide chain (protein chain).
• Hemoglobin + oxygen = oxyhemoglobin.
• White blood cells help the immune system fight infection
  • There are 2 types: Lymphocytes (responsible for antibody production, and cell-mediated killing of virus-infected/tumor cells) and Neutrophils (ingest bacteria/virus and release enzymes that kill them).
• Platelets help with blood clotting to prevent bleeding and repair tissue.

Heart Parts

• Superior vena cava carries blood from head/neck/arms/chest and returns deoxygenated blood to the heart from head and arms.
• The pulmonary valve allows blood flow from the right ventricle to the pulmonary artery, helping oxygen-poor blood reach the lungs where it gains oxygen and loses CO2.
• Pulmonary veins carry oxygen-rich blood from lungs to heart.
• The right atrium receives oxygen-poor blood & empties it into the right ventricle.
• The tricuspid valve ensures blood flows from right atrium into right ventricle.
• The right ventricle accepts venous blood and propelling it to the lungs where it gains oxygen and loses CO2.
• Inferior vena cava carries oxygen-depleted blood back to the heart from the lower part of the body.
• The septum helps keep oxygen-rich blood from the lungs from mixing with oxygen-poor from the body.
• The left ventricle pumps oxygenated blood to the body.
• The bicuspid valve prevents blood from flowing back from the aorta into the heart when the pumping chamber relaxes.
• The left atrium receives oxygenated blood from lungs via pulmonary veins and delivers it to the left ventricle.
• Pulmonary arteries carry oxygen-poor blood from heart to the lungs.
• The aorta transports oxygen-rich blood from heart to the rest of the body.

Types of Capillaries

• Fenestrated capillaries have perforations, apertures or transparent areas.
• Sinusoid capillaries are irregularly shaped blood vessels found in certain organs, especially the liver.
• Continuous capillaries are tiny blood vessels that deliver blood, nutrients and oxygen to cells.

Arteries

• Arteries send blood away from the heart.
• They have high pressure due to blood having to be pumped to the entire rest of the body.
• The lumen diameter is narrow (because walls are thick).
• Walls are thick to withstand high blood pressure to prevent rupturing.
• Walls have three layers: tunica adventitia, tunica media, and tunica intima
• Contains a large amount of muscle & elastic fibers that allow walls to stretch/expand with each pulse of blood through the lumen; elastic recoil: when artery returns back to normal size that pressure is exerted on arterial wall which pushes the blood.
• Arteries have no valves.

Veins

• Veins send blood to the heart.
• They have low pressure.
• The lumen diameter is wide.
• Walls are thin.
• Walls have three layers: tunica adventitia, tunica media, and tunica intima.
• Contains a small amount of muscle & elastic fibers, where contractions of skeletal muscles surrounding veins help force blood upwards against gravity.
• Veins have valves to prevent backflow of blood.

Capillaries

• Capillaries allow for material exchange with tissue
• They have a low pressure.
• The lumen diameter is very narrow.
• Walls are extremely narrow and consist of one: tunica intima.
• No muscle & elastic fibers present.
• Capillaries do not have valves

Respiratory System

Components

• Nasal cavity
• Pharynx
• Larynx
• Trachea
• Lungs
• Bronchi
• Bronchioles
• Alveoli
• Diaphragm

Ventilation and Gas Exchange

• Ventilation includes the movement of air into and out of the lungs consisting of inspiration & expiration (controlled by movement of the diaphragm and the intercostal muscles).
• Gas exchange includes the diffusion of oxygen and CO2 that occurs in the alveoli of the lungs and tissues.
• Gases move from area of high concentration to low concentration.
• Breathing brings oxygen, as well as increase the concentration of oxygen between the alveoli and blood and allows oxygen will diffuse into blood.
• Breathing out removes CO2, as well as increasing the concentration gradient of CO2 between blood and alveoli, allowing CO2 will diffuse into alveoli.

Alveolar Adaptations for Gas Exchange

• Thin wall: small distance for diffusion
• Rich capillary network: efficient amount of gas exchange
• Large surface area: efficient gas exchange
• Moist: prevent alveoli from collapsing

Learn about the intricate process of the digestive system, including mechanical and chemical breakdown, peristalsis, and digestion in the stomach and small intestine. Understand the roles of enzymes like amylase, hydrochloric acid, and pepsin in breaking down food materials into absorbable nutrients.