Ross & Wilson Anatomy and Physiology in Health and Illness (212 page)

Infections of the penis

Inflammation of the glans and prepuce may be caused by a specific or non-specific infection. In non-specific infections, or
balanitis
, lack of personal hygiene is an important predisposing factor, especially if
phimosis
is present, i.e. the orifice in the foreskin (prepuce) is too small to allow for its normal retraction. If the infection becomes chronic there may be fibrosis of the foreskin, which increases the phimosis.

Infections of the urethra

Gonococcal urethritis is the most common specific infection. Non-specific infection may be spread from the bladder (cystitis) or be introduced during catheterisation, cystoscopy or surgery. Both types may spread throughout the system to the prostate, seminal vesicles, epididymis and testes. If infection becomes chronic, fibrosis may cause urethral stricture or obstruction, leading to retention of urine.

Epididymis and testes

Infections

Non-specific epididymitis and orchitis are usually due to spread of infection from the urethra, commonly following prostatectomy. The microbes may spread either through the deferent duct (vas deferens) or via lymph.

Specific epididymitis

This is usually caused by gonorrhoea spread from the urethra.

Orchitis (inflammation of the testis)

This is commonly caused by mumps virus, blood-borne from the parotid glands. Acute inflammation with oedema occurs about 1 week after the appearance of parotid swelling. The infection is usually unilateral but, if bilateral, severe damage to germinal epithelium of the seminiferous tubules may result in sterility.

Undescended testis (cryptorchidism)

During embryonic life the testes develop within the abdominal cavity, but descend into the scrotum prior to birth. If they fail to do this and the condition is not corrected, infertility is likely to follow and the risk of testicular cancer is increased.

Hydrocele

This is the most common form of scrotal swelling and is accumulation of serous fluid in the tunica vaginalis. The onset may be acute and painful or chronic. It may be congenital or be secondary to another disorder of the testis or epididymis.

Testicular tumours

Most testicular tumours are malignant, the commonest malignancies in young men. They occur in childhood and early adulthood when the affected testis has not descended or has been late in descending into the scrotum. The tumour tends to remain localised for a considerable time but eventually spreads in lymph to pelvic and abdominal lymph nodes, and more widely in the blood. Occasionally, hormone-secreting tumours develop and may cause precocious development in boys.

Prostate gland

Infections

Acute prostatitis is usually caused by non-specific infection, spread from the urethra or bladder, often following catheterisation, cystoscopy, urethral dilation or prostate surgery. Chronic infection may follow an acute attack. Fibrosis of the gland may occur during healing, causing urethral stricture or obstruction.

Benign prostatic enlargement

Hyperplastic nodules form around the urethra and may obstruct the flow of urine, causing urinary retention. Urethral stricture may prevent the bladder emptying completely during micturition, predisposing to infection, which may spread upwards, causing pyelonephritis and other complications. Prostatic enlargement is common in men over 50, affecting up to 70% of men aged over 70. The cause is not clear, but it may be an acceleration of the ageing process associated with the decline in androgen secretion, which changes the androgen/oestrogen balance.

Malignant prostatic tumours

These are a relatively common cause of death in men over 50. The carcinogen is not known but changes in the androgen/oestrogen balance may be significant or viruses may be involved. Invasion of local tissues is widespread before lymph-spread metastases develop in pelvic and abdominal lymph nodes. Blood-spread metastases in bone are common and bone formation rather than bone destruction is a common feature. Lumbar vertebrae are common sites, possibly due to retrograde spread along the walls of veins. Bone metastases are often the first indication of malignant prostatic tumours.

Breast

Breast tissue in men consists of ducts and stroma only.

Gynaecomastia

This is proliferation of breast tissue in men. It usually affects only one breast and is benign. It is common in adolescents and older men, and is often associated with:

•
endocrine disorders, especially those associated with high oestrogen levels

•
cirrhosis of the liver (
p. 325
)

•
malnutrition

•
some drugs, e.g. chlorpromazine, spironolactone, digoxin

•
Klinefelter’s syndrome, a genetic disorder with testicular atrophy and absence of spermatogenesis.

Malignant tumours

These develop in a small number of men, usually in the older age groups.

Male infertility

This may be due to:

•
endocrine disorders

•
obstruction of the deferent duct

•
failure of erection or ejaculation during intercourse

•
vasectomy

•
suppression of spermatogenesis by, e.g., ionising radiation, chemotherapy and other drugs.

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Glossary

Abduction
Movement of a body part away from the midline of the body

Accommodation
Focussing adjustment of the eyes to view close objects

Acid
Substance that releases hydrogen ions in solution

Acidosis
Situation when blood pH falls below the normal pH range

Action potential
The electrical current (impulse) conducted along a nerve cell (neurone)

Active transport
Movement of substances across a cell membrane, up the concentration gradient, and requiring energy

Acute
Of sudden onset

Adaptation
Lessening of response by sensory receptors to prolonged stimulation

Adduction
Movement of a body part towards the midline of the body

Adenosine triphosphate (ATP)
Molecular store of chemical energy for chemical reactions

Adipose tissue
Fat tissue

Aerobic
Requiring oxygen

Aetiology
Cause of a disease

Afferent
Carrying or travelling towards an organ

Afterload
The resistance to blood flow from the heart, determined mainly by the diameter of the arteries

Agranulocyte
White blood cell with no granules in its cytoplasm (i.e. lymphocytes and monocytes)

Alkali
Substances that accepts hydrogen ions in water or solution

Alkalosis
Situation when blood pH rises above the normal pH range

Allele
The form of a gene carried on a chromosome

Alveolar ventilation
The amount of air reaching the alveoli with each breath

Alveolus (pl. alveoli)
An air sac in the lungs; also the milk secreting sacs in the mammary glands

Amino acid
The building blocks of protein

Anabolism
Synthesis of larger molecules from smaller ones

Anaerobic
Not requiring oxygen

Anaphase
Third phase of mitosis

Anastomosis
A blood vessel (except a capillary) joining two blood vessels

Anatomical position
Used to maintain consistency of anatomical descriptions – the body is upright, with the head facing forward, the arms at the sides with the palms of the hands facing forward, and the feet together

Aneurysm
A weakness in the wall of an artery

Anion
A negatively charged ion

Anterior (ventral)
Describes a body part nearer the front

Antibody
Defensive protein synthesised by B-lymphocytes in response to the presence of antigen

Antigen
A protein that stimulates the body’s immunological defences

Antimicrobial
A substance or mechanism that kills or inhibits growth of micro-organisms

Appendicular skeleton (cf. axial skeleton)
The shoulder girdle, upper limbs, pelvic girdle and lower limbs

Arrhythmia
An abnormal heart rhythm

Arteriole
A small artery

Artery
A blood vessel that carries blood away from the heart

Articulation
A joint

Autoregulation
The ability of a tissue to independently control its own blood supply

Autorhythmicity
The ability of a tissue to generate its own electrical signals

Autosome
Any one of the chromosomes in pairs 1–22 (i.e. all but the sex chromosomes)

Axial skeleton (cf. appendicular skeleton)
The skull, vertebral column, sternum (breastbone) and ribs

Bacterium (pl. bacteria)
Single-celled micro-organism, common in the external environment, some of which can cause disease

Baroreceptor
Sensory receptor sensitive to pressure (stretch)

Basal metabolic rate
The energy use of the body when at rest in a warm environment, without having eaten for 12 hours

Benign
Non-cancerous or a non-serious condition for which treatment may be required

Bradycardia
Abnormally slow heart rate

Bronchodilation
Widening of the larger airways and bronchioles

Buffer
A substance that resists a shift in pH of body fluids

Capacitance vessel
A vessel that can expand to contain large quantities of blood at low pressure (veins)

Capillary
A tiny blood vessel between an arteriole and a venule, which has leaky walls to allow exchange of substances between the blood and tissues

Carbohydrate
Group of organic compounds including the sugars and starches

Carcinogen
A cancer-causing substance

Carcinoma
A tumour arising from epithelial tissue

Cardiac output (CO)
The amount of blood ejected by one ventricle every minute: CO = heart rate (HR) × stroke volume (SV)