biology part 2

Multicellular organisms

Made up of many different specialized cells (ex

Unicellular organisms

Single-celled organisms (ex

Cells

The simplest units that can carry out all life processes.

Tissues

Collections of similar cells that perform a particular, but limited, function.

Epithelial tissue (epithelium)

Thin sheet of tightly packed cells that covers body surfaces and lines internal organs and body cavities (ex

Connective tissue

Specialized tissue that provides support and protection for various parts of the body (ex

Muscle tissue

Specialized tissue containing proteins that can contract and enable the body to move (ex

Nerve tissue

Specialized tissue that conducts electrical signals from one part of the body to another (ex

Organs

Structures composed of different tissues working together to perform a complex body function.

Organ systems

Systems of one or more organs and structures that work together to perform a major, vital body function.

Cellular differentiation

As cells divide, they develop differences in shape, contents, and function and become specialized.

DNA (genetic information)

Cellular differentiation is directed by genetic information in a cell’s DNA, passed from parent to offspring.

Stem cells

Undifferentiated cells that can divide to form specialized cells; what they become depends on which parts of DNA are switched on.

Embryonic stem cells (pluripotent)

Stem cells that can differentiate into any kind of cell; come from embryos.

Tissue stem cells (multipotent)

Stem cells in specialized tissue (sometimes called adult stem cells) that can only become certain cell types depending on where they are located.

Bone marrow tissue stem cells

Can differentiate into white blood cells, red blood cells, or platelets.

Stem cell treatment for leukemia

Bone marrow stem cells from a matched donor are injected into a leukemia patient’s bone marrow to regenerate healthy, cancer-free blood cells after chemotherapy.

Tissue regeneration with stem cells

Because some cells (ex

Digestive system

Organ system that takes in food, digests it, absorbs nutrients, and excretes remaining waste; made of the digestive tract and accessory organs.

Digestive tract

The pathway food follows

Mechanical digestion

Physical breakdown of food.

Chemical digestion

Breakdown of food by enzymes and chemicals.

Teeth

Incisors, canines, premolars, and molars tear, grind, and crush solid food masses (mechanical digestion).

Tongue

Manipulates food during chewing and pushes it back to the molars.

Salivary glands

Located on the sides of the mouth; produce amylase (enzyme) and help moisten food.

Amylase

Chemical enzyme in saliva that breaks down starch.

Bolus

Moistened, ball-like mass of food formed in the mouth that moves into the digestive tract.

Pharynx

Passage the bolus moves through on the way from the mouth toward the esophagus.

Epiglottis

“Trap door” that prevents food from entering the trachea.

Esophagus

Muscular tube (~2 cm diameter) connecting the mouth to the stomach.

Cardiac sphincter

Point of connection between the esophagus and stomach; prevents reflux of food from stomach to esophagus.

Peristalsis

Series of muscle contractions in the digestive tract; in the esophagus it moves the bolus down into the stomach.

Stomach

J-shaped organ used to store and digest food; both mechanical and chemical digestion occur here.

Stomach mechanical digestion

Smooth muscle tissue contracts and churns the bolus.

Stomach chemical digestion

Enzymes and acids (“digestive juices”) chemically break down food particles for absorption.

Chyme

Liquefied paste produced after stomach digestion.

Pyloric sphincter

Controls the release of chyme from the stomach into the small intestine.

Small intestine

Major site of digestion and absorption into the bloodstream.

Small intestine parts

Duodenum, jejunum, ileum.

Small intestine length

Approximately 6 m long; called “small” because of its diameter.

Accessory organs (digestive)

Liver and pancreas help digestion by supplying digestive enzymes.

Liver

Produces bile.

Bile

Fluid that breaks down large fat molecules into smaller molecules; secreted into the duodenum.

Pancreas

Secretes pancreatic juice containing digestive enzymes that further break down carbohydrates, proteins, and fats in the duodenum.

Insulin

Hormone produced by the pancreas that regulates blood glucose concentration.

Diabetes

Develops when there isn’t enough insulin in the bloodstream or the body cannot properly use insulin; without insulin, glucose can’t enter cells and blood glucose can rise to life-threatening levels.

Large intestine (colon)

Main function is reabsorbing water and vitamins; about 1.5 m long and larger in diameter than the small intestine.

Rectum

Last part of the large intestine where undigested matter and toxins are stored.

Feces

Remaining solid matter that is excreted from the anus.

Circulatory system

Provides the force and channels to distribute blood, which carries food and oxygen to cells and removes wastes.

Coronary circuit

Circulation within the heart.

Pulmonary circuit

Circulation that pumps blood to the lungs.

Systemic circuit

Circulation that pumps blood to the body.

Double pump

Blood passes through the heart twice each circuit; right side pumps deoxygenated blood to lungs, left side pumps oxygenated blood to body tissues.

Closed circulatory system

Blood is always enclosed in blood vessels and does not directly contact body tissue cells; vessels are found almost everywhere to allow exchange.

Arteries

Thick-walled elastic muscle tubes that expand with pressure; carry blood away from the heart; branch into arterioles; aorta is the principal artery from the heart.

Veins

Thin-walled tubes that carry blood back to the heart; contain valves to prevent backflow due to low pressure; small veins are venules; vena cava is the principal vein into the heart.

Capillaries

Fine network of thin-walled (one cell layer) tubes around tissues; allow diffusion quickly; oxygen/nutrients move into cells and CO₂/wastes move into capillaries.

Aneurysm

Bulging blood vessel that can rupture and cause stroke, internal bleeding, and death.

Varicose veins

Valve failure causes backflow of blood; enlarges superficial veins in legs or rectum (hemorrhoids).

Blood volume

A 70 kg person has about 5 L of blood.

Blood (fluid tissue)

Blood is a “fluid” tissue, meaning individual cells work together for a common purpose.

Importance of blood

Transports gases, wastes, nutrients/hormones; fights disease and infection; enables blood clotting.

Red blood cells (erythrocytes)

Most numerous blood cells; contain hemoglobin to carry oxygen; produced in bone marrow; lifespan ~120 days; lack a nucleus; body can stimulate RBC growth when oxygen is reduced (ex

Hemoglobin (circulatory)

Iron-containing molecule in red blood cells that carries oxygen to body cells.

White blood cells (leukocytes)

Fight germs and foreign harmful cells; lifespan from a few days to a few weeks; contain a nucleus.

Platelets

Small particles that initiate blood clotting when there is a cut in the skin.

Plasma

The fluid of blood; contains dissolved substances important to maintain body functions.

Anemia

Insufficient hemoglobin in red blood cells reduces oxygen-carrying capacity; causes tiredness/low energy; iron supplements often help.

Leukemia

Cancer of the blood; increased number of white blood cells in circulation; these white blood cells are immature and can’t fight disease.

Heart (cardiac muscle)

Composed of cardiac muscle that beats involuntarily; averages ~72 beats/min; two sides separated by septum.

Septum

Muscular wall that separates the two sides of the heart.

Systole

Contraction of the heart muscle.

Diastole

Relaxation of the heart muscle.

Atrium

Thin-walled heart chamber that receives blood from veins.

Ventricle

Muscular, thick-walled heart chamber that delivers blood to arteries.

Heart chambers

Four chambers total (right atrium, right ventricle, left atrium, left ventricle); blood flows atrium → ventricle.

Coronary artery disease

Coronary arteries supply heart muscle; arteries can become partially blocked with plaque (fat, cholesterol, calcium, other substances); symptoms include tiredness, dizziness, pain/burning in arms or chest; diagnosed with an angiogram.

Heart attack

Coronary artery can be completely blocked by plaque or a blood clot; heart muscle cells stop receiving oxygen/nutrients, pumping stops, and tissue starts to die; symptoms include chest pain/pressure, shortness of breath, nausea, anxiety, sweating, dizziness; diagnosed with blood test and ECG; life-threatening.

Respiratory system (daily breathing)

You take about 17,000 to 29,000 breaths per day; a deep breath captures about 3–4 L of air; breathing is too important to be left to conscious control.

Trachea

Tube that takes air from the back of the throat down to the lungs; supported by cartilage rings to keep it open; lined with mucus-producing cells and cilia.

Larynx

Voice box located before the trachea.

Bronchi

Two tubes formed when the trachea splits near the lungs; one bronchus leads to each lung.

Alveoli

Tiny air sacs surrounded by blood vessels; lungs contain millions; where gas exchange occurs.

Pathway of air

Nose/mouth → pharynx/larynx → trachea → bronchi → bronchioles → alveoli.

Mucus (trachea)

Secreted by mucus-producing cells to trap dust and other airborne particles.

Cilia (trachea)

Sweep trapped material out of the trachea (wave-like motion) so it can be swallowed or expelled by coughing/sneezing.

Gas exchange (alveoli)

Alveoli fill with air to allow diffusion; many alveoli provide large surface area; walls are a thin single layer of flattened cells; surrounded by dense capillary network to remove CO₂ and transport O₂.

Hemoglobin (respiratory)

Protein in red blood cells that picks up O₂ from the alveoli and transports it to the rest of the body.

How we breathe (muscles)

Uses diaphragm (large dome-shaped muscle under lungs) and muscles between ribs; breathing is involuntary but can be overridden temporarily while talking.

Breathing control (CO₂)

Controlled by a part of the brain that detects blood CO₂; if CO₂ rises, the brain signals the diaphragm and heart to increase breathing rate and heart rate, decreasing CO₂ and increasing O₂.

Inhalation

Air entering lungs; diaphragm contracts (moves downward) and ribcage expands outward.

Exhalation

Air exiting lungs; diaphragm relaxes (moves upward) and ribcage moves inward.

Tuberculosis (TB)

Infectious disease caused by bacteria; symptoms include fever, cough, weight loss, tiredness, chest pain; diagnosed using chest X-ray and examination of stomach or lung secretions.

SARS

Severe Acute Respiratory Syndrome; spread from a region of China to 37 countries; Canada identified 438 cases and 44 deaths; symptoms include flu-like illness, high fever, shortness of breath, dry cough, sore throat, headache, muscle pain, exhaustion; diagnosed using chest X-ray showing pneumonia and positive lab results of cell samples.

Respiratory system cancers

Caused mostly by tobacco smoke (first- or second-hand); carcinogens contribute to cancers of the mouth, lungs, larynx, pancreas, esophagus, and bladder.

COPD (Chronic Obstructive Pulmonary Disease)

About 90% caused by smoking; chronic, progressive disease involving obstructive bronchitis and emphysema.

Obstructive bronchitis

Long-term cough, inflammation, and mucus (similar to asthma).

Emphysema

Permanent damage to alveoli; they lose elasticity and shape, decreasing surface area for gas exchange.

COPD cure status

No cure; damage to alveoli is permanent.