Year 11 Human Bio Glossary A - E

Sooooo I decided that now I've gone through the book, I'd create a glossary. This is for two reasons: 1) it's a different format of presenting the information, and I find that it often helps to see information in at least two different formats and 2) it could be a useful resource for you to create your own flashcards or study tools. I'll try not to go into too much detail in the glossary- if you need extra details on anything, go to the relevant post(s) (there's a search bar at the top if you haven't noticed it already), Google it, or look it up in your textbook. NOTE: I don't know what the "official WACE Human Bio definition" is for anything, so don't copy what I have to say verbatim. Understanding the concepts is more important than memorisation anyway.

With regards to flashcards, I am overwhelmingly in favour of flashcard apps like Anki (there are loads of others, like SuperMemo, Repetitions and so on- I just mentioned Anki first because it's probably the most well-known), since they save you from having to physically make flashcards and also they use spaced repetition to help you remember more things with less effort. Also, you can download these apps onto your phone (iOS users have to pay quite a bit for Anki though- might be time to switch to Android eh?) so that wherever you've got your phone, you've got a very useful study tool. Of course, if you prefer physical flashcards, that's your call.

Other sections of the glossary: (F - J) (K - O) (P - T) (U - Z)

A

Abduction- Movement away from the midline of the body.
Abnormal uterine bleeding- Very heavy periods, periods that are too frequent, bleeding during non-menstrual phases and bleeding after menopause.
Accessory ligaments- Ligaments holding together bones in many joints.
Acetabulum- A socket located in each pelvic bone. Forms part of the hip joint.
Active transport- Energy is used in order to forcibly absorb substances against a concentration gradient (i.e. force a substance to move from a place of low concentration to a place of higher concentration).
Adduction- Movement towards the midline of the body.
Adenine- One of the nitrogen bases present in DNA and RNA. Pairs up with thymine.
Adipose tissue- A type of connective tissue that cushions vital organs and restricts heat loss. Consists of cells that contain large globules of fat with the cytoplasm forming a thin layer on the outside.
Adolescent growth spurt- The period during which adolescents rapidly grow taller.
Aerobic respiration- Cellular respiration requiring oxygen.
Afterbirth- The placenta, umbilical cord, amnion and chorion which are expelled after birth.
Agonist- The muscle in the pair that carries out the desired action. Opposite to this is the antagonist. The agonist is also known as the prime mover.

Agranular leucocyte- A leucocyte that doesn't have any granules in its cell contents and usually has a spherical nucleus. Includes monocytes and lymphocytes.

Albumin- A type of plasma protein which is like the proteins found in egg whites.

Alimentary canal- The tube in which digestion takes place. Runs from the mouth to the anus and includes the pharynx, oesophagus, stomach and intestines.
Allantois- One of the embryonic membranes. Will become part of the umbilical cord.
Altitude sickness- Higher altitudes contain lower pressure air (i.e. fewer gas molecules in the same amount of space as compared to lower altitudes). People who aren't used to the lower pressures may feel sick as their bodies are unable to absorb enough oxygen. Also known as mountain sickness.
Alveoli (singular: alveolus)- Tiny air sacs that make up most of the area of the lung. Exchange of gases between the blood and the lungs takes place here, as the alveoli have very thin walls (one cell thick). They contain thin layers of moisture, allowing them to dissolve gases.

Amino acids- The building blocks of proteins. There are about 20 different amino acids. Some are part of the structural material in the cell and some are enzymes in cellular reactions, while excess proteins are either converted to carbohydrates to be used as energy or stored as fats.
Amniocentesis- A method used to check for birth defects. 10-20mL of amniotic fluid containing living cells from the foetus is removed. The cells can be checked for abnormalities in biochemistry or in number/structure of the chromosomes.
Amnion- One of the embryonic membranes. Secretes amniotic fluid into a cavity surrounding the embryo. Will eventually fuse with the inner layer of the chorion.
Amniotic fluid- A fluid that protects the embryo from physical injury and maintains a constant temperature while allowing the foetus to move around. Expands while the foetus grows and ruputures just before childbirth.
Anabolism- Chemical reactions that create large molecules from several smaller ones.

Anaemia- A condition in which the number of red blood cells or the concentration of haemoglobin is reduced, resulting in inadequate oxygen supply to the tissues, which in turn results in symptoms such as fatigue and intolerance to cold.
Anaerobic respiration- Cellular respiration without oxygen.

Anal sphincter- The muscle around the anal opening that controls bowel movements.
Anaphase- The stage of cell division where the chromatids begin to separate off into different parts of the cell.

Angina- Chest pain normally caused by atherosclerosis of the coronary arteries.

Animalia- The kingdom (highest taxonomic rank) that contains animals (including humans).
Antagonist- The muscle within the pair that does not cause the desired action. Opposite of this is the agonist.
Antagonists- Pairs of muscles. The two muscles in the pair carry out opposite effects.
Anterior tibialis- A muscle located at the front of the lower leg. Allows us to point our toes upwards, taking weight onto the heels.

Anthropoidea- A suborder within the Primates order which consists of "human-like primates" such as monkeys, apes and humans.

Antigens- Substances that can stimulate the formation of antibodies. Red blood cells can contain antigen A and/or B, or neither antigen A or B.

Anus- The opening at the end of the rectum. Faeces pass through here.

Aorta- The main artery of the body. Takes blood from the left side of the heart to other organs of the body.

Appendicitis- Inflammation of the appendix. Could be caused by blockage of the appendix by faecal matter or a foreign body, but there may be other causes as well.
Appendicular skeleton- The bones that make up the ribs as well as the shoulders and hips.

Appendix- A part of the large intestine located at the end of the caecum opposite the entrance to the colon.
Arboreal- Live in trees.

Arteries- Relatively large blood vessels that take blood away from the heart. They have thick, strong walls with smooth muscle that allows them to stretch and relax to maintain blood pressure.

Arterioles- Small arteries. Like arteries, they have thick, strong walls with smooth muscle, allowing them to stretch and relax in order to maintain blood pressure.

Arteriosclerosis- Hardening and narrowing of the arteries.
Arthritis- Inflammation of the joints.
Articular cartilage- Cartilage located on the epiphyses of the bones, providing smooth surfaces for movement.
Articular disc- A structure that divides the synovial cavity into two, allowing synovial fluid to be directed to areas of greatest friction.
Articulate- When bones are positioned in such a way that they can move relative to each other, they are said to articulate.
Artificial insemination by donor (AID)- A reproductive technology in which the woman accepts semen donated by an unknown man.

Ascending colon- The part of the colon that goes from the caecum upwards.
Assistive reproductive technology (ART)- Reproductive technology which involves the fertilisation of an egg and sperm outside of the uterus. The resulting embryo is then transplanted into the woman's uterus. There are several different types.
Asthma- An allergic response which results in the muscles surrounding the bronchioles going into spasm (sudden involuntary contractions) and excessive mucus being secreted, causing difficulties in breathing.

Atherosclerosis- A type of arteriosclerosis in which hard, calcified areas cause obstructions, resulting in the artery walls losing their elasticity.

Atrial systole- A stage of the cardiac cycle, lasting roughly 0.1 seconds. During this phase, the atrium contracts, forcing blood into the ventricles. Meanwhile, the ventricles stay relaxed, ready to receive the blood rushing in.

Atrioventricular valve- A valve in the heart that allows blood to pass from atrium to ventricle, but not the other way. Consist of flaps as well as chordae tendinae. The atrioventricular valve of the left side has two cusps (and is thus called the bicuspid valve), while that of the right side has three cusps (and is thus called the tricuspid valve).

Atrium- The first chamber that the blood enters when it enters the heart through the veins. Has relatively thin walls as incoming blood is low-pressure.
Atrophy- The decrease in size of a muscle. Normally happens in muscles that aren't used or are only used for very weak contractions.

Autologous transfusion- A transfusion in which the patient's own blood (donated in advance) is used.
Axial skeleton- The bones surrounding the central "axis" of the body (i.e. the skull, backbone and ribs)

B

Ball-and-socket joint- A joint in which one bone has a spherical head, while the other has a kind of cup-like cavity for the spherical head to fit into. Allows movement in all directions. Examples: shoulder joint, hip joint
Balloon angioplasty- A treatment for atherosclerosis in which a patient is first given drugs that help to dissolve clots, and then a tube with a tiny balloon at the tip is inserted into the patient's arteries. The balloon is inflated to cause the artery to expand and the plaque to loosen from the wall.
Basal metabolic rate (BMR)- The amount of energy required when resting.
Belly- The middle section of a muscle.
Benign tumour- A tumour that does not spread to other parts of the body, as its cells cannot invade normal tissues, blood vessels or lymph vessels.
Bicuspid valve- The atrioventricular valve on the left side of the heart, so called due to its two cusps.
Bile pigments- A component of bile. Bile pigments are the end result of red blood cells breaking down. They have no digestive function and are excreted in the faeces.
Bile salts- A component of bile that is necessary for emulsifying fat (breaking it up into lots of pieces that can't be mixed back together), increasing the surface area, so that enzymes can break fat down more efficiently.
Bipedal- Walks on two legs.
Birth canal- The curved passage made up of the uterus, cervix and vagina following the dilation of the cervix. The baby travels through here to be born.
Blastocyst- A hollow ball of cells formed around 5 days after fertilisation (1-2 days after the morula stage). One side has a bunch of cells collectively known as the inner cell mass.
Blood clotting- A series of processes that allow blood clots to form. Also known as coagulation.
Bolus- A lump of food held together by mucus in the saliva.
Bonding- A term used to refer to the love and affection between parent and child.
Brachialis- A muscle that lies beneath the biceps. Allows us to flex our forearms.
Breech presentation- The foetus is positioned with buttocks down rather than head down at birth.
Bronchi (singular: bronchus)- Tubes that bring air in and out of the lungs. They have cartilage like the trachea, and a ciliated mucous membrane.
Bronchioles- Smaller bronchi that lack cartilage and cilia.
Bronchitis- An irritation that causes an increase in mucus production in the bronchi and bronchioles, which can result in an accumulation of mucus which can be cleared by coughing.
Bulbo-urethral glands- Two small yellow glands located beneath the prostate gland. Secrete a clear mucus which mainly acts as a lubricant, thogh a small amount does get inclued in the semen as well. Also known as the Cowper's glands.
Bursae- Little sacs of synovial fluid. Only present in some joints. Bursae are positioned in such a way to prevent friction in certain parts of the joint.

C

Caecum- A 6cm pouch at the beginning of the large intestine. It ends in the appendix.
Calcanean tendon- The tendon at the end of the gastrocnemius muscle. Also known as the Achilles' tendon.
Calcaneus- The largest of the ankle bones. Also known as the "heel bone."
Canaliculi- Small canals that run between lacunae in compact bone. Allow materials to be passed between cells.
Cancellous bone- Porous bone tissue that contains many large spaces. Also known as spongy bone.
Canines- Teeth used for tearing and ripping.
Capillaries- Microscopic blood vessels that form complex networks, allowing them to carry blood to nearly every cell. They have very thin walls (only one cell thick), allowing substances to diffuse in and out of them more easily.
Carbaminohaemoglobin- A compound formed when carbon dioxide combines with the globin part of the haemoglobin molecule. It can break down to allow carbon dioxide to diffuse into the alveoli.
Carbohydrates- Chains of sugars that contain carbon, hydrogen and oxygen. They are necessary for providing energy to the body cells. Excess carbohydrates are stored as glycogen in the liver and muscles, but if there's too much then the remaining excess gets converted into fat.
Carbon monoxide poisoning- Carbon monoxide (CO) can combine with haemoglobin 250 times more readily than oxygen can. When CO combines with haemoglobin, the oxygen-carrying capacity of the blood is reduced.
Carcinogen- A factor that triggers the growth of a tumour.
Carcinoma- A type of cancer that forms from epithelial cells on the inner and outer surfaces of the body. Around 90% of cancers are carcinomas.
Cardiac arrest- The heart pumps little to no blood. Can result in death within minutes.
Cardiac cycle- A fancy way of saying "heartbeat."
Cardiac muscle- Muscle making up the wall of the heart. Has cross-striations like skeletal muscle, but unlike skeletal muscle, cardiac muscles branch to form a network.
Carotid arteries- Arteries that take blood to the head and neck.
Carpals- Wrist bones. There are eight of them in each wrist.
Cartilage- A type of connective tissue that provides structural support while still providing some flexibility. Has fibres embedded in a firm matrix which also contains spaces for the cartilage cells.
Cartilaginous joints- Joints in which bones are held together by cartilage. Slight movement can occur, but not a lot. Also known as slightly moveable joints.
Castration- Removal of the testes.
Catabolism- Chemical reactions that break down larger molecules into smaller ones.
Cell membrane- A structure that separates the cell from neighbouring cells and the external environment. It is made up of a double layer of lipid molecules as well as various proteins associated with the lipids. Allows some substances to get through but not others. Also known as the plasma membrane.
Cellular respiration- A metabolic process in which the organic molecules from the food are broken down to release energy for the cells.
Cellulose- A long-chain carbohydrate that can be found in foods of plant origin, particularly unrefined foods.
Cementum- The outer layer of the tooth on the root side. Anchors the teeth to the jaw bone.
Centrioles- A pair of cylindrical structures, which are made up of rings of very fine tubules. The centrioles are located at right angles to each other. They are located near the nucleus and are involved in cellular reproduction
Centromere- The point at which two chromatids join in a chromosome.
Cephalocaudal pattern- A pattern involved in motor development. Movements of the upper parts of the body develop before those of the lower parts of the body.
Cerebral cortex- The outer region of the brain. Responsible for complex functions such as vision, memory, reasoning and manipulative ability.
Cerebral haemorrhage- Bleeding that occurs at a weak point in one of the cerebral arteries.
Cervix- A structure at the lower end of the uterus that protrudes into the vagina. Contains a narrow passage known as the cervical canal.
Chlamydia- An STD caused by a bacteria. Affects many parts of the body.
Chordata- Our phylum. Contains creatures that have spinal cords running down their backs, attached to a brain at one end (a.k.a. a "dorsal nerve cord").
Chordae tendinae- Fibrous chords that stop the flaps of the atrioventricular valve from swinging too far.
Chorion- A membrane that develops from the outer cells of the blastocyst and a layer of mesodermal cells. Surrounds the embryo and the other three embryonic membranes. Eventually becomes the main part of the foetal portion of the placenta. Produces HCG.
Chorionic villi- Finger-like projections that are formed from the cells of the chorion. Contain numerous blood vessels. Provide a large surface area to make contact with the mother's blood, allowing nutrients, oxygen and waste products to diffuse back and forth between the mother's blood and the baby's blood. Active transport may also be used.
Chorionic villus sampling (CVS)- A method used to check for birth defects. Foetal cells from the chorion are checked for abnormalities.
Chromatid- A structure in a chromosome. There are two chromatids in a chromosome.
Chromatin- Strands of DNA.
Chromosomal mutation- A mutation involving a cell receiving too many or too few chromosomes, or parts of chromosomes.
Chylomicrons- Tiny droplets that enter the lacteals, formed from fatty acids and glycerol recombining to form triglycerides which are then coated with protein.
Chyme- A soupy liquid formed after the food has been digested in the stomach.
Cilia- Hair-like projections located in the mucous membrane of the lower part of the nasal cavity, in the trachea and in the bronchi. Beat back and forth in order to push dust etc. towards the throat. As well as moving substances over cells, cilia can also move the whole cell.
Circular muscle- Muscle in which the fibres are arranged in a circle. Can be found in the alimentary canal.
Clavicle- Collar bone.
Cleavage- The process in which the zygote divides repeatedly to form a ball of cells called a morula.
Cleft lip- A birth defect in which the upper lip is split.
Cleft palate- A birth defect that occurs when the bones of the hard palate (the front part of the roof of the mouth) don't come together before birth. Associated with cleft lip.
Clitoris- A small structure located within the folds of the labia minora (in females). Contains erectile tissue, blood vessels and nerves.
Clot- Formed by cells trapped in the blood by threads of insoluble protein. Stops too much blood from flowing out of a torn blood vessel.
Clot retraction- A process in which the threads of insoluble protein making up a clot contract, becoming denser and stronger and pulling the edges of the blood vessels together. Serum is squeezed out during this process. After clot retraction, the clot dries and forms a scab, protecting the wound from infections.
Clotting factors- Chemical substances in the plasma that allow threads of insoluble protein to form, which trap cells, forming a clot.
Coagulation- A series of processes that allow blood clots to form. Also known as blood clotting.
Co-factors- Ions or non-protein molecules necessary for enzyme functioning.
Coitus- Sexual intercourse.
Coitus interruptus- An extremely unreliable form of contraception involving the man removing his penis before ejaculation.
Colostrum- A watery, yellowish-white fluid secreted by the breasts. Has a similar composition to milk, but contains little to no fat, and a high content of the mother's antibodies, which are then absorbed by the infant's intestine to give the baby temporary immunity to certain diseases.
Columnar cells- Column-shaped cells.
Common bile duct- A duct through which pancreatic juice and bile pass in order to get to the duodenum.
Compact bone- A type of compact tissue that is found in bones.
Complete proteins- Proteins containing sufficient quantities of essential amino acids. Same as first-class proteins.
Concentration gradient- The difference in concentration that allows diffusion to occur. Same as diffusion gradient.
Conchae- The "shelves" within each chamber of the nasal cavity.
Congenital disorder- A disease or defect which is present at birth due to either defective genes or environmental factors.
Congestive heart failure- The heart is too weak to pump sufficient amounts of blood. Also known simply as "heart failure."
Connective tissue- Tissue that binds and supports the other tissues of the body.
Convulsions- Violent, involuntary contractions. May be caused by muscle fibres receiving impulses from nerves, which in turn might have been stimulated by fever, poisons and so on.
Corona radiata- A layer of cells surrounding the ovum prior to fertilisation. The cells are held together by an acid, which has to be broken down by the enzymes contained within the heads of the sperm cells.
Coronary artery- An artery that takes blood to the heart itself.
Coronary heart disease- A disease in which atherosclerosis in the coronary arteries restricts the supply of blood to the heart muscle so that there might not be enough oxygen supply to the heart.
Corpus albicans- A fibrous mass of scar tissue formed after the corpus luteum degenerates.
Corpus luteum- The cream coloured body formed when the blood within a ruptured Graafian follicle clots and is absorbed by the remaining follicle cells. Secretes hormones that influence the development of the lining of the uterus.
Cortex- The outer portion of the brain. Has a lot of folds, called convolutions, which increase the surface area of the brain.
Cowper's glands- Two small yellow glands located beneath the prostate gland. Secrete a clear mucus which mainly acts as a lubricant, though a small amount does get included in the semen as well. Also known as the bulbo-urethral glands.
Cramps- Sustained involuntary muscular contractions that lack even partial relaxation.
Cranium- The part of the skull used for housing the brain.
Crown- The part of the tooth that is visible.
Cryoprecipitate- A transfusion created by freezing the plasma and allowing other substances to thaw out. Contains substances necessary for blood clotting.
Cuboidal cells- Cube-shaped cells.
Cytoplasm- Fluid within the cell. It is 75% to 90% water. Inorganic materials and most carbohydrates are dissolved in it, while other organic compounds such as proteins and lipids are simply suspended in it.
Cytosine- One of the nitrogen bases present in DNA and RNA. Pairs up with guanine.
Cytoskeleton- A structure that gives the cell its shape and assists the cell in moving. Consists of microtubules and microfilaments.

D

Daughter cell- A term used to refer to the new cells after cell division has occurred.
Dead space (respiratory system)- The interior of the organs of the respiratory system that are not involved in exchange of gases.
Deamination- A process through which excess amino acids are converted to carbohydrates. In this process, the -NH2 amine group is removed and converted to ammonia (NH3), which is then converted to urea. Urea is then removed from the blood by the kidneys before being excreted in urine.
Deciduous teeth- Baby teeth (the first set of teeth that you have).
Defecation- A fancy way of saying "shitting."
Dense connective tissue- A type of connective tissue that supports and connects other tissues. Stronger than loose connective tissue, making it more suitable for joining tendons to bones and so on.
Dentine- A layer of the tooth below the enamel and cementum. It is hard and bone-like and comprises much of the tooth.
Deoxygenated blood- Blood that has a lower concentration of oxygen. It is dark red in colour, as haemoglobin is dark red.
Deoxyribonuclease- A digestive enzyme in the pancreatic juice that breaks down DNA.
Descending colon- The third part of the colon. Goes down towards the rectum and anus.
Diaphragm- The muscle separating the thoracic and abdominal cavities. Can contract and relax to alter the volume of the thoracic cavity.
Diaphysis-The shaft of a typical long bone.
Diastole- The heart muscles are relaxed, allowing blood to flow into the atria and/or ventricles.
Differentially permeable membrane- A membrane that allows some substances to pass through but not others.
Differentiation- The specialisation of different cells to carry out different functions.
Diffusion- The spreading out of the particles of a gas or liquid over a given area so that they become evenly distributed.
Diffusion gradient- The difference in concentration that allows diffusion to occur. Same as concentration gradient.
Dipeptide- Two amino acids joined together.
Diploid cell- A cell containing a full set of chromosomes (46 in humans).
Disaccharide- Two simple sugars (monosaccharides) joined together. One example is sucrose.
Dislocation- A bone is displaced, and ligaments, tendons or capsules are torn. Symptoms include temporary paralysis of the joint, pain, swelling and occasionally shock.
Dorsal nerve chord- A spinal cord that runs down the back of an animal attached to its brain at one end. Shared by all creatures in the phylum Chordata.
Double circulation- The type of circulation used all birds and mammals, including humans. In this type of circulation, the blood is pumped by the heart twice in each circuit, keeping the blood moving rapidly and stopping it from losing too much pressure.
Down syndrome- A birth defect caused by having three of the chromosome number 21. Symptoms include mental retardation and malformation of the heart, ears, hands and feet. The risk increases as the mother reaches the end of her child-bearing period. Also known as trisomy-21.
Ductus arteriosus- The lung bypass present in unborn babies. Takes blood from the pulmonary artery to the aorta. Turns into fibrous tissue within a few weeks of birth due to the reduced amount of blood flowing through it.
Ductus venosus- The liver bypass. A vein in unborn babies that allows blood to bypass the liver. Blood stops flowing through the ductus venosus after birth, causing it to constrict until it is closed off, forcing all blood to pass through the liver instead.
Duodenum- The first C-shaped curve of the small intestine. It is about 25cm long.
Dysmenorrhoea- Painful menstruation caused by strong contractions of the uterus.

E

Ectopic pregnancy- A pregnancy where the blastocyst implants itself somewhere other than the uterus. Can be serious, causing internal bleeding or damage to the Fallopian tubes.
Ejaculation- Rhythmic contractions of the epididymis, the vas deferens, the seminal vesicles and the prostate gland, which push the sperm-containing semen out of the body.
Elasticity- The ability of muscles to return to their original length after being stretched.
Embryo- An organism at the stage between implantation of the blastocyst in the uterus and the development of limbs. Humans remain embryos for around two months before becoming a foetus.
Emphysema- Caused by long-term exposure to irritating particles. The particles damage the alveoli, which lose their elasticity, are replaced with fibrous tissue, and may break down. The loss of elasticity means that the lungs are constantly inflated, which then means that exhalation requires voluntary effort.
Enamel- The outer layer of the tooth on the crown side. It is the hardest substance in the body and is used to protect the teeth.
Endocrine gland- A gland that secretes substances directly into the blood or into the tissue fluid.
Endocytosis- A method of absorbing substances. The outer membrane folds around the substance in question, leaving the substance floating around the cytoplasm in a liquid-filled sac called a vesicle.
Endometrium- The soft mucous membrane lining of the uterus. Protects and nourishes the foetus during pregnancy.
Endoplasmic reticulum- Pairs of parallel membranes that extend through the cytoplasm and connect to the cell membrane and nuclear membrane. There are two types: rough (granular) endoplasmic reticulum and smooth (agranular) endoplasmic reticulum. The main difference is that the former has ribosomes attached to it, while the latter does not. The membranes of the endoplasmic reticulum is thought to provide a surface where chemical reactions can take place, while the channels are for storing or transporting molecules.

Enzyme- Organic catalysts (i.e. they speed up the reactions of living organisms without being consumed in the reaction). They are proteins.

Enzyme-substrate complex- Formed from the reaction with an enzyme and a substrate.
Epididymis- A tubule in which sperm are stored for up to a month while they mature.
Epididymitis- Pain and swelling of the epididymis.
Epiglottis- A flap of cartilage located at the entrance to the larynx. It closes the glottis during swallowing, stopping food from passing into the trachea and lungs.
Epiphyses (singular: epiphysis)- The ends of bones.
Epithelial tissue- Tissue used to cover body surfaces and line body cavities and ducts. Its functions include absorption, secretion and protection, depending on the location of the tissue in the body. Also known as the epithelium.
Epithelium- Tissue used to cover body surfaces and line body cavities and ducts. Its functions include absorption, secretion and protection, depending on the location of the tissue in the body. Also known as the epithelial tissue.
Erectile tissue- A type of connective tissue in the penis. Has a very rich blood supply. Contains a number of sponge-like spaces, which can fill with blood, causing an erection.

Erythrocytes- Blood cells that transport oxygen to the cells. They are red in colour, hence their other, more common name, red blood cells.

Essential amino acids- Amino acids that cannot be produced in the body. There are nine of these.
Eustachian tube- A tube that leads to the inner ear.
Exocrine gland- A gland that secretes substances outside the body, or onto a body lining.
Exocytosis- A method of eliminating substances from the cell. Vesicles containing the unwanted substances are pushed out of the cell.
Expiration- Exhalation/breathing out.
Extensibility- The ability of muscles to be stretched.
Extension- Movement causing the angle between bones to increase.

Extracellular fluid- Fluid outside the cells. Includes tissue fluid and plasma.