• Arteries are thick walled and elastic to handle the pressurized flow.
• Veins are thinner walled because blood pressure is lower, and they have valves to help blood return to the heart.
• Blood returns to the heart through major veins; the superior vena cava and inferior vena cava.
• After leaving the capillaries, the blood is deoxgenated
• Blood is carried back to the heart through small venules which turn into larger veins.
Components of Blood
• Blood transports materials around the body.
• The average person has 5L of blood of which 55% is plasma, a straw coloured liquid containing dissolved minerals, and nutrients.
• The 40 to 50% of the blood volume is red blood cells (RBC) or erythrocytes
• 1% of blood volume is white blood cells (WBC) or leukocytes
• The remainder of blood is composed of platelets or thrombocytes.
• Red blood cells carry oxygen in a protein called hemoglobin. Hemoglobin is what causes RBC to appear red.
• The RBC lack nuclei, so they cannot reproduce, but they are made in bone marrow.
• White blood cells fight infection, and there are may types of WBC all of which are larger and more distinct looking than RBC
• Platelets are cell fragments without nuclei that work with blood clotting chemicals at the site of wounds
Problems with Circulatory System
• The most common causes of heart disease are hypertension (high blood pressure) and arteriosclerosis.
• If a clot breaks free, it may flow to a coronary artery and block a blood vessel, causing a heart attack.
• If the blood clot stops blood flow to the brain it is called a stroke.
• An angioplasty is shown.
• Arteriosclerosis is the thickening of the walls of the arteries.
• These can cause formation of a blood clot.
• Purpose: gas exchange. Bringing oxygen (O2) into the body, and removing carbon dioxide (CO2).
• The respiratory system is interconnected with the circulatory system.
• The main structure, the lungs are connected to the outside by passageways.
• Air enters through the mouth and nose, and travels down the trachea. The trachea separates into two branches called bronchi (singular bronchus)
• The lining of the trachea and bronchi produce mucus, and many of the epithelial cells have cilia (hairlike projections).
• The cilia and mucus filter out any foreign material that might enter the system.
• The trachea is supported by rings of cartilage, keeping it open.
• Each bronchus further splits into smaller branches called bronchioles, and these branches end in tiny air sacs called alveoli (singular alveolus).
• Oxygen enters the bloodstream in the lungs by diffusion, and carbon dioxide leaves in the same way.
• Alveoli have very thin walls, and are surrounded by a network of capillaries.
• Oxygen and carbon dioxide only have to diffuse through two thin walls.
• The blood that enters the lungs has little oxygen. As the blood flows through the lungs it picks up oxygen and the blood returns to the heart.
• At the same time, excess carbon dioxide diffuses out of the blood, into the airspaces of the alveoli.
• The respiratory system involves the process called breathing, which involves moving air into and out of the lungs.
• This process involves the muscles that move the ribs, making the ribcage expand and contract, and a large sheet of muscle under the lungs, called the diaphragm.
• Together the diaphragm and muscles of the ribs increase or decrease the volume of the lungs. As the volume changes, the pressure also changes. In this way fresh air flows into and out of the alveoli.
• Control over our breathing is involuntary; we do not generally have to think about breathing. We can override the involuntary system and stop breathing, but this control is only temporary.
• Control of breathing occurs in part of your brain and detects carbon dioxide levels in the blood.
• As the CO2 level increases the brain sends signals to increase breathing rate, and heart rate.
• This decreases the concentration of carbon dioxide in the blood, and also increases available oxygen.
• Purpose: To mechanically and chemically break down food to nutrient molecules that are absorbed and used throughout the body.
What are the major nutrients in our diet?
– Carbohydrates glucose
– Fats, lipids fatty acids
– Proteins amino acids
– *Nucleic acids nucleotides
• What are the micronutrients?
– Vitamins and minerals
• There are 4 main jobs within the digestive system:– Ingestion: taking in
– Digestion: mechanical and chemical breakdown
– Absorption: nutrients pass into bloodstream
– Elimination: removal of wastes.
• The four stages of food processing
Chemical digestion(enzymatic hydrolysis)
Nutrient moleculesenter body cells
INGESTION1 DIGESTION2 ELIMINATION4ABSORPTION3
Human Digestive System
• Human digestive system is basically one long tube, and various accessory glands that secrete digestive juices through ducts.
A schematic diagram of thehuman digestive system
Oral Cavity, Pharynx and Esophagus
• Digestion begins in the mouth with mechanical digestion by teeth which chew food into smaller particles.
• Salivary glands release saliva into the mouth to lubricate food. Saliva also contains an enzyme amylase, which chemically breaks down starch into sugars.
• The tongue shapes food into a bolus that is swallowed.
Pharynx and Esophagus
• As food is swallowed it makes its way to the pharynx, a junction that opens to both the esophagus and the trachea.
• The esophagus moves food from the pharynx down to the stomach by peristalsis.
• Peristalsis is the rhythmic movement of the smooth muscle surrounding the digestive tract.
• Swallowing causes the epiglottis to block entry to the trachea.
Glottis upand closed
• The stomach stores food and secretes gastric juice.
• Gastric juice is made up of hydrochloric acid and an enzyme called pepsin.
• The stomach also secretes mucus which protects the stomach lining from gastric juice.
• Coordinated contraction and relaxation of stomach muscle churn the stomach’s contents.
• Sphincters, rings of muscle, prevent materials from entering the esophagus, and regulate entry into the small intestine.
Small Intestine: first section
• The small intestine is the longest section of the digestive tract.
• It is the major organ of digestion and absorption.
• The small intestine is broken into three sections.
• In the first section, the acidic material from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and the small intestine itself.
• The pancreas produces enzymes that break apart carbohydrates, lipids and proteins.
• The pancreas also releases a basic solution to neutralize the acidic materials entering from the stomach.
Liver & Gallbladder
• In the small intestine, bile helps with the digestion of fats.
• Bile acts as an emulsifier that allows fats to better mix with the watery enzymes.
• Bile is made in the liver, and is stored until needed in the gallbladder.
Small intestine: second and third sections
• The second and third sections of the small intestine have a huge surface area due to villi and microvilli.
• This great amount of surface area increases the rate of nutrient absorption.
• Each villus contains a network of blood vessels.
• The capillaries and venules come together in the vein that leads to the liver, and then on to the heart.
Microvilli (brushborder) at apical(lumenal) surface
Vein carrying bloodto hepatic portal vein
• The colon or large intestine connects to the small intestine.
• A major function of the colon is to recover water that has entered the digestive tract.
• Wastes of the digestive tract, the feces, become more solid as they move through the colon.
• The colon contains many bacteria including E. coli, which produces some vitamins.
• Feces are stored in the rectum until they are eliminated through the anus.