Human Biology

Dr Robert M. Youngson

• Publisher: Collins
• Year: 2017
• Print ISBN: 9780007221349
• eBook ISBN: 9780007556649
• Topic: Biological Sciences
• Subtopic: Biology
• Index: Biological Sciences

Aa

a- prefix denoting not, without or the absence of a quality or object.

AASH adrenal androgen-stimulating hormone.

ab- prefix denoting from, outside, away from. From the Latin ab, from.

A band the dark band on muscle sarcomere corresponding to the length of the myosin filament.

ABC genes genes that code for the ATP-binding cassette transporter proteins that carry compounds across biological membranes. Fourteen different ABC genes are known to be associated with human genetic diseases.

ABC transporter proteins a large and diverse family of cell membrane transport proteins with two transmembrane domains and two ATP-binding regions within the cytosol. The transmembrane domains provide a controllable pathway for transported substance to pass through the cell membrane into or out of the cell.

ABCA3 gene a gene that codes for a 1704-amino-acid protein found in the limiting membrane of lamellar bodies. Mutations of this gene cause fatal SURFACTANT deficiency in newborn babies.

ABCA4 gene a gene that codes for a transporter protein found in the photoreceptor membrane disks in retinal rod cells.

ABCB1 member 1 of the B subfamily of ABC TRANSPORTER PROTEINS. Also known as MDR1.

ABCG5 genes genes coding for transporter proteins found in the liver and intestines.

ABCG8 genes genes with a function similar to that of ABCG5 GENES.

abdomen the part of the trunk below the chest. The abdominal cavity lies between the DIAPHRAGM, above, and the pelvic floor, below. It contains the LIVER and most of the digestive system, comprising the STOMACH, the DUODENUM, the JEJUNUM, the ILEUM, the CAECUM with the APPENDIX, the COLON, the RECTUM and the ANAL CANAL. Other abdominal organs include the KIDNEYS, the ADRENAL GLANDS, the SPLEEN, the PANCREAS and some large and important blood vessels, such as the AORTA and the inferior VENA CAVA, around which are many chains of LYMPH NODES. The intestines are hung from the back wall of the abdomen by a much-folded membrane, the MESENTERY, and are covered by the OMENTUM. The lower part of the abdomen, the pelvic cavity, contains the BLADDER. In women, the pelvic cavity also contains the womb (UTERUS), the FALLOPIAN TUBES and the OVARIES; in men, the central PROSTATE GLAND and the VAS DEFERENS, on each side. The wall of the abdomen consists of overlapping layers of muscle and sheets of fibrous tissue. The organs and the interior of the walls are covered with PERITONEUM. See also ABDOMINAL REGIONS.

abdominal referring to the ABDOMEN.

abdominal breathing respiration in which most of the work is done by the muscles of the abdominal wall in compressing the abdominal contents and elevating the diaphragm so as to compress the lungs and push out air.

abdominal quadrant any one of the four areas on the front of the abdomen formed by two imaginary lines, one vertical and one horizontal intersecting at the navel. The four quadrants are called upper and lower right and upper and lower left, as seen from the person’s point of view.

abdominal region any one of the nine areas into which the surface of the abdomen is divided for descriptive purposes. Centrally, from above down, are the epigastric, umbilical and hypogastric (pubic) regions, and on either side, from above down, are the hypochondriac, lateral and inguinal regions.

abdominoperineal relating to the ABDOMEN and to the PERINEUM.

abdominous having a large belly. Pot-bellied.

abducens nerves the sixth of the 12 pairs of cranial nerves. Each abducens nerve supplies the tiny muscle on the outer side of the eye that moves the eye outwards (the lateral rectus muscle). Also known as abducent nerve.

abducent causing a separation. The word derives from the Latin ab, from, and ducere, to draw or lead. See also ABDUCTION.

abduction a movement outwards from the mid-line of the body or from the central axis of a limb. The opposite, inward, movement is called ADDUCTION.

abductor muscle a muscle which moves a part away from the mid-line.

aberrant deviating from the normal. The term may be applied to variations in the fine detail of body structure, such as the size and position of small arteries, or to modes of behaviour not generally considered acceptable. See also ABNORMAL.

aberration a deviation from normal. The term derives from the Latin aberrare, to wander off. See also ABNORMAL.

-ability combining form denoting power or capacity to do something.

abiogenesis the theory of ‘spontaneous generation’ – the long-discarded notion that living organisms can be formed from non-living matter. Louis Pasteur’s work (see PASTEURIZATION) did much to overthrow this idea which was based largely on the observation that maggots often appeared on rotting meat.

abiotic non-living.

abiotrophy a general and inexact term referring to the effects of ageing, or to any degenerative process of unknown cause affecting tissue, especially nerve tissue. As knowledge extends the need for such terms diminishes.

ablactation weaning.

ablation the removal of any part of the body.

abnormal deviating from the observed rule or from the consensus opinion of what is acceptable. ABERRANT. See also ABNORMALITY.

abnormality the condition of not conforming to standard recognized patterns of structure, function, behaviour or phenomenon. In some social contexts, normality is no more than a statistical concept, and may be entirely relative. What is normal in one population or group may be abnormal in another. See also ABERRATION.

abnormal psychology a branch of psychology dealing with disorders of behaviour and mental disturbance, and with certain normal phenomena not clearly understood, such as dreams and altered states of consciousness. See also ABERRATION.

ABO blood groups a system of blood grouping developed from the discoveries of Karl Landsteiner (1868–1943) in 1900. The designations are arbitrary and the four groups are A, B,AB and O. These represent the antigenic differences in the red cells, the ANTIGEN being present on the red cell membranes. Group A, B and AB people have A, B and A and B antigens, respectively, on their red cells. Group O people have no antigens and are known as universal donors, whose blood, other things being equal, may safely be transfused into anyone. Group A people (about 26 per cent in Europe) have antibodies (agglutinins) to B in their serum and must not be given blood with B antigens. Agglutinins cause red cells with the same letter antigens to clump together and to become useless. Group B people (about 6 per cent) have antibodies to A in their serum and must not be given blood with A antigens. Group O people (about 68 per cent) have both A and B antibodies, so must not be given either A or B blood. Group AB people have no ABO blood group antibodies in their serum and are known as universal recipients. See also RHESUS FACTOR DISEASE and KELL BLOOD GROUP SYSTEM.

abreaction a process used in PSYCHOTHERAPY in which repressed thoughts and feelings are brought into consciousness and ‘relived’. Abreaction is, it is hoped, followed by CATHARSIS and is most readily achieved when the trouble arises from a recent traumatic event.

absolute refractory period the period during which no stimulus, however strong, is able to evoke a response from an excitable tissue. The absolute refractory period follows immediately after a prior response and is brief.

absolute temperature temperature expressed in the Kelvin scale with absolute zero as o kelvin. The magnitude of the kelvin is the same as that of the degree Celsius and any Celsius temperature can be represented as an absolute temperature by degrees C – 273.15. The term ‘degree kelvin’ is no longer used; absolute temperatures are shown in kelvins (William, Lord Kelvin, British physicist, 1824–1907).

absorption 1 the movement of liquids and of dissolved substances across a membrane, from one compartment of the body to another or into the blood.

2 the assimilation of digested food material into the blood from the small intestine. Compare ADSORPTION. See also DIGESTION.

absorption spectrum the range of wavelengths of light that are absorbed by a pigment, such as the melanion of the skin.

abuse incorrect, improper or excessive use or treatment.

abzyme an antibody that has an enzyme-like (catalytic) action.

acanth-, acantho- combining form denoting spine or the prickle cell layer of the skin.

acanthoid resembling a thorn or spiny process.

acapnia absence of CARBON DIOXIDE in the BLOOD or tissues. This cannot occur in life and the term is usually applied imprecisely to a reduced level of CO₂.

acceleration stress the effects on body function and behaviour of periods of exposure to increased gravitational forces (‘g’) such as are experienced by fighter pilots or astronauts.

accent the speech patterns and pronunciation characteristic of a particular geographic region or social class. Accent sends out strong signals, the reaction to which may be one of reassurance, identification, respect, suspicion, resentment or hostility.

acceptor sites 1 DNA base sequences that bind transcription regulators, 2 Molecules that bind other chemical groups (also known as acceptor molecules).

access...

Table of contents

• Title Page
• Copyright
• Dedication
• Contents
• Preface
• Aa
• Bb
• Cc
• Dd
• Ee
• Ff
• Gg
• Hh
• Ii
• Jj
• Kk
• Ll
• Mm
• Nn
• Oo
• Pp
• Qq
• Rr
• Ss
• Tt
• Uu
• Vv
• Ww
• Xx
• Yy
• Zz
• Human Biology Resources on the Internet
• About the Author
• About the Publisher