We love our bodies, don’t we? It’s just so nice to understand what’s going on inside of all of this skin.
Basic Human Body Science
The eleven systems of the human body: Skeletal system, respiratory system, muscular system, nervous system, digestive system, reproductive system, circulatory system, endocrine system, lymphatic/immune system, integumentary system, urinary system
Skeletal system: The framework of bones and cartilage that supports the body and provides hard surfaces for the muscles to contract on
The four types of bones: Flat (example: ribs), long (example: legs), irregular (example: spine), short (example: fingers)
Important bones: Cranium (skull), mandible (jawbone), scapula (shoulder blades), clavicle (collar bone), sternum (breastbone), humerus (upper arm), rib, vertebral column (spine, made of vertebrae), radius (lower arm on top), ulna (lower arm underneath), carpals (wrist bones), metacarpals (finger bones), pelvis (hip bones, including the pelvis), coccyx (butt bone), femur (high leg bone), patella (kneecap), tibia (top shinbone), fibula (bone under fibia) metatarsals (foot bones), tarsals (ankle bones), phelanges (finger and toe/digit bones)
Joint: The places where bones meet. Most joints are movable.
Bone marrow: The store of fat inside the bone cavity
Cartilage: The alternative to bone that’s more flexible. Most baby bones are actually cartilage and slowly turn into bone later.
Muscular system: The system that enables the body to move using muscles
Muscles: Stretchy tissues all over the body that allow for movement. Some pairs work together with one contracting as the other relaxes. They can only contract and relax, not push.
Muscle contraction: The movement that occurs when muscles become shorter and harder and may bulge
Muscle relaxation: The movement that occurs when muscles become longer and softer
Types of muscles: Muscles are either voluntary (requiring conscious movement, such as the quads) or involuntary (such as the heart). They are also either skeletal (located on the skeletal system), cardiac (the heart and related muscles) or visceral (the intestines).
Nervous system: The system that collects and processes information from the senses via nerves and the brain and tells the muscles to contract to cause physical actions. It is made up of the sensory organs, the brain, the spinal cord and the nerves. The nervous system coordinates both voluntary and involuntary body movements.
Peripheral nervous system: The whole network of nerves throughout the body
Neurons: Nerve cells. They include sensory, association and motor nerves cells.
Nerves: Cords that contain bundles of nerve fibers. Can be sensory, motor and mixed (both).
Spinal cord: The thick bundle of nerves that joins the brain to the rest of the body. It is located inside a tunnel in the backbone.
Nerve impulse: An action of a neuron
Neurotransmitters: Various chemicals such as serotonin and epinephrin that allow neurons to communicate with each other. These are sometimes called “chemical messengers.”
Neurotransmission: The communication that takes place between neural networks
Reflex action/reflex: An involuntary and nearly instantaneous movement in response to a stimulus
Brain: The organ under the skull that is made up of millions of neurons and cerebrospinal fluid. There are electrical impulses going on between nerve cells in brain all the time. Brain waves (patterns of impulses) can be measured.
Left brain hemisphere:
Right brain hemisphere:
The three main parts of the brain:
Brain stem: Controls automatic functions like heartbeat and breathing. It contains two hemispheres: right and left.
Cerebrum: (for physical activities and thinking),
Cerebellum: (for muscle movement and balance)
Diencephalon: (with thalamus, which sorts and directs incoming impulses) and hypothalamus
Hypothalamus: (which controls hunger, thirst, body temperature, release of hormones from pituitary gland).
The lymbic system:
REM sleep: Rapid eye movement sleep (REM sleep, REMS) is a unique phase of sleep in mammals and birds, distinguishable by random/rapid movement of the eyes, accompanied with low muscle tone throughout the body, and the propensity of the sleeper to dream vividly.
Sensory organs: Organs that send nerve impulses (signals) to the brain along nerves
Motor nerves: Nerves that receive signals from the brain to the muscles to move
How eyes work: Light enters the pupil through the clear cornea and lens. These bend the light rays so they form an image on the retina and back of eye. (Turns image upside down.) Rods and cones convert the image to nerve impulses which take the optic nerve to the brain. The brain interprets and turns the image right side up.
Stereoscopic vision: Perception of depth and 3-dimensional structure obtained on the basis of visual information deriving from two eyes
Ear: The hearing organ. It contains an outer, middle and inner part.
How ears work: The ear flap funnels sound waves to the ear canal, then to the eardrum. The eardrum vibrates. These vibrations pass through bones and holes to the cochlea, then to fluid chambers. Tiny nerve cells in the fluid convert vibrations into nerve impulses, which go along the auditory nerve to the brain. Ears also help keep you balanced through the vestibular system. This works by sensing movement of fluid in ducts and sending that info to the brain. Since you have two ears you can tell which direction sound is coming from.
Chemoreceptors: Small organs in the nose and tongue that detect smells and tastes, which are chemicals, and send this information to the brain.
Nasal cavity: The large air filled space above and behind the nose in the middle of the face
Digestive system: The system responsible for the mechanical and chemical processes that provide nutrients via the mouth, esophagus, stomach and intestines and eliminates waste from the body.
Liver: The organ that allows us to go between meals without eating by storing food energy. It is the largest organ by mass. Extra energy beyond the liver capacity is stored as fat. The liver also processes waste materials we encounter in our environment.
Circulatory system: The system that circulates blood around the body via the heart, arteries and veins, delivering oxygen and nutrients to organs and cells and carrying their waste products away. It also equalizes the temperature in the body. It includes blood, blood vessels and the heart.
Parts of the heart: Four chambers (two atria and two ventricles), valves to keep blood moving the right direction through the heart (each time one snaps shut there’s a heartbeat), veins and arteries that carry blood from heart to lungs, upper body and lower body and others for the opposite direction.
Arteries: Move blood away from the heart
Integumentary system: Skin, hair, nails, sweat and other exocrine glands
Skin: The soft outer tissue covering of vertebrates. It contains the epidermis, the dermis and subcutaneous tissues (fat cells).
Melanin: Natural pigments found in most organisms
Pores: Tube-shaped sweat glands
Keratin: What skin and nails are made of
Hair follicle: The opening at the base of a hair. Its shape determines whether the hair is curly, wavy or straight.
Respiratory system: The lungs and the passages that lead to them and allow for breathing of oxygen and breathing out of CO2.
Windpipe/trachea: A tube that connects the pharynx and larynx to the lungs, allowing the passage of air
Primary bronchus: The tubes between the trachea and each lung. After passing through the bronchus, air goes into the lungs. Then oxygen goes into secondary and tertiary bronchi, bronchioles, air sacs and capillaries and from there is distributed throughout the body.
Lung: A large air sack containing many tubes
Diaphragm: A flat sheet of muscle lying under the lungs. When you breathe in, your ribs move up and out and the diaphragm flattens. When you breathe out, your ribs move down and in and the diaphragm rises.
Voice box/larynx: Top part of the trachea
Vocal cords: Two bands of muscle that open to let air past when you breathe. When you speak muscles pull the cords together and air makes them vibrate. Shorter, faster cords, as in females, make higher pitched sounds.
Internal respiration: The movement of oxygen from the outside environment to the cells within tissues, and the transport of carbon dioxide in the opposite direction.
Metabolism: The set of life-sustaining chemical reactions in organisms
Aerobic respiration: Internal respiration that uses oxygen
Anaerobic respiration: Doesn’t use oxygen
Enzymes: Macromolecular biological catalysts. Enzymes accelerate chemical reactions.
Thermogenesis: The process of heat production in organisms
ATP: Adenosine triphosphate, an organic chemical that provides energy to drive many processes in living cells, e.g. muscle contraction, nerve impulse propagation, and chemical synthesis.
Basal metabolic rate (BMR): The rate of energy expenditure per unit time by an animal at rest
Calorie/kilocalorie: A unit of energy. A calorie is the amount of heat energy needed to raise the temperature of one gram of water by one degree Celsius at a pressure of one atmosphere, and the kilocalorie is the heat energy required to raise the temperature of one kilogram (rather than a gram) of water by one degree Celsius.
Lactic acid: An important body acid
Endocrine system: The system that provides chemical communications within the body using hormones
Endocrine glands: Groups of cells that make hormones.
Hormones: Any member of a class of signaling molecules produced by glands in multicellular organisms that are transported by the circulatory system to target distant organs to regulate physiology and behaviour. The body makes over 20 types of hormones.
Pituitary gland: Makes growth hormone, prolactine, which control other endocrine glands, growth, mother’s milk production
Parathyroids gland: Makes parathormone which controls calcium levels in blood and bones.
Adrenals: The twin glands that make adrenalin and aldosterone which control blood glucose level, heart rate, body’s salt level
The thyroid gland: Makes thyroxin which controls metabolism
The pancreas: Makes insulin and glucagon which control the use of glucose by the body
Urinary/renal system: The system that controls the amount of water in your body and filters blood. It includes two kidneys, a balloon-like sac called the bladder and the tubes connected to them.
Urethra: The tube that connects the bladder to the urinary meatus for the removal of urine from the body
Kidneys: The two bean-shaped organs on the left and right in the retroperitoneal space. They are about 11 centimetres in length. They receive blood from the paired renal arteries; blood exits into the paired renal veins. Each kidney is attached to a ureter, a tube that carries excreted urine to the bladder.
Lymphatic/immune system: The system comprising a network of lymphatic vessels that carry a clear fluid called lymph. It defends the body against pathogenic viruses that may endanger the body. The lymph contains the leftover interstitial fluid resulting from blood filtration.
Lymph: Lymph is the fluid that circulates throughout the lymphatic system
Lymph node: A kidney-shaped organ of the lymphatic system, and of the adaptive immune system, that is widely present throughout the body. Lymph nodes are major sites of white blood cells and important for the immune system.
Reproductive system: The sex organs required for the production of offspring
Reproduction: The process of creating offspring
Male reproductive system parts: Penis, testicles, sperm, prostate gland, and scrotum
Penis: The primary sexual organ that male animals use to inseminate sexually receptive mates
Glans: A vascular structure located at the tip of the penis in males or a genital structure of the clitoris in females
Foreskin: The the double-layered fold of smooth muscle tissue, blood vessels, neurons, skin, and mucous membrane part of the penis that covers and protects the glans penis and the urinary meatus
Sperm/spermatoza: The male reproductive cell
Semen: The fluid made in the testicles that may contain sperm
Testicle: The testicle or testis (plural testes) is the male reproductive gland in all animals, including humans. It produces sperm and semen.
Prostate gland: A gland of the male reproductive system
Scrotum: The suspended dual-chambered sack of skin and smooth muscle that holds the two testacles
Female reproductive system parts: The uterus, Fallopian tubes, and ovaries
Ovulation: The release of eggs from the ovaries
Ovum: The egg cell. (The plural form of the word is “ova”.)
Menstruation/having a period: The (approximately) monthly discharge of blood and mucosal tissue (known as menses) from the inner lining of the uterus through the vagina
Menopause: The time in women’s lives when menstrual periods stop permanently, and they are no longer able to bear children
Vagina: The elastic, muscular canal leading to the uterus in which sex takes place
Cervix: The lower part of the uterus that contracts and opens during childbirth
Fallopian tubes: The tubes leading from the ovaries to the uterus
Womb/uterus: The organ in which fetal development takes place.
Labia: The major externally visible portions of the vulva. It has two layers.
Sexual intercourse: The insertion and thrusting of the penis, usually when erect, into the vagina for sexual pleasure, reproduction, or both. This is also known as vaginal intercourse or vaginal sex. Other forms of penetrative sexual intercourse include anal sex (penetration of the anus by the penis), oral sex (penetration of the mouth by the penis or oral penetration of the female genitalia), fingering (sexual penetration by the fingers), and penetration by use of a dildo.
Ejaculation: The discharge of semen (normally containing sperm) from the male reproductory tract, usually accompanied by orgasm
Fertilization/conception: The union of a human egg (ovum) and sperm, usually occurring in the fallopian tube of the mother after sex
Embryo: The newly conceived form of life between the fertilized egg (zygote) stage and the fetus stage
Fetus: The unborn baby who is past the embryonic stage (about nine weeks into the pregnancy)
Placenta: The temporary organ that connects the developing fetus via the umbilical cord to the uterine wall to allow nutrient uptake, thermo-regulation, waste elimination, and gas exchange via the mother’s blood supply; to fight against internal infection; and to produce hormones which support pregnancy
Umbilical cord: The conduit between the developing fetus and the placenta inside a pregnant woman
Puberty: The process of physical changes through which a child’s body matures into an adult body capable of sexual reproduction
Adolescence: The phase of life after puberty and between childhood and adulthood; the teen years
Basic Medical Science
Disease: Anything that stops all or part of your body from working properly (other than injury)
Infection: The invasion of an organism’s body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxins they produce
Immunity: The balanced state of multicellular organisms having adequate biological defenses to fight infection, disease, or other unwanted biological invasion, while having adequate tolerance to avoid allergy, and autoimmune diseases
Drug: A drug is any substance (other than food that provides nutritional support) that, when inhaled, injected, smoked, consumed, absorbed via a patch on the skin, or dissolved under the tongue causes a temporary physiological (and often psychological) change in the body
Nutrients: The vitamins, minerals, and proteins that are used to make body parts, either by facilitating a chemical reaction or by being used as actual material (like calcium an amino acids from protein breakdown), and the carbs and fats that are burned for fuel.
Preventive medicine: Measures taken for disease prevention, as opposed to disease treatment
Diagnosis: The identification of the nature and cause of a certain phenomenon
Bacteria: A type of biological cell. Among the first life forms to appear on Earth, and are present in most of its habitats. Most have not been discovered or studied.
Virus: A virus is a small infectious agent that replicates only inside the living cells of other organisms
White blood cell: The cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders
Vaccination: The administration of antigenic material (a vaccine) to stimulate an individual’s immune system to develop adaptive immunity to a pathogen
Antibiotics: A substance that kills bacterial. Not antiviral.
Pathogen: A germ, usually a microorganism like a bacteria or virus that can cause illness or disease
Tumor: An abnormal and excessive growth of tissue that starts as a neoplasm, then forms a mass
In vitro fertilization (IVF): A process by which egg cells are fertilized by sperm outside the womb, in vitro.
Contraception: Birth control
Senescence: The gradual deterioration of functional characteristics due to age
Medical imaging: Creating images of the internal organs to help diagnose and treat disease
CT scan: Computed tomography scan. Formerly CAT scan. Uses computer-processed combinations of many X-ray measurements taken from different angles to produce cross-sectional images of internal organs.
MRI scan: Magnetic resonance imaging. Uses magnets and radio waves (not X-rays, as CT scans do) to create images of the internal organs.
Surgery: The use of knives, lasers and other instruments to explore inside the body or change or remove something in the body
Laser surgery: Laser surgery is a type of surgery that uses a laser (in contrast to using a scalpel) to cut tissue.
Alternative medicine: Unproven or disproven medical techniques and substances
Acupuncture: An unproven traditional Chinese alternative medicine in which thin needles are inserted into the body.