Medical Applications

• Parkinson disease

  • slowly progressing disorder affecting muscular activity characterized by tremors, reduced activity of the facial muscles, loss of balance, and postural stiffness
  • caused by gradual loss by apoptosis of dopamine-producing neurons whose cell bodies lie within the nuclei of the CNS substantia nigra
  • treated with L-dopa (L-3,4-dihydroxyphenylalanine), a precursor of dopamine that augments the declining production of this neurotransmitter.
• Most local anesthetics are low-molecular-weight molecules that bind to the voltage-gated sodium channels of the axo-lemma, interfering with sodium ion influx and, consequently, inhibiting the action potential responsible for the nerve impulse.
• Selective serotonin reuptake inhibitors (SSRIs)

  • a widely used class of drugs for treatment of depression and anxiety disorders, were designed to augment levels of this neurotransmitter at the postsynaptic membrane of serotonergic CNS synapses by specifically inhibiting its reuptake at the presynaptic membrane.
• astrocytomas

  • most brain tumors
  • derived from fibrous astrocytes
  • distinguished pathologically by their expression of GFAP
• Alzheimer disease

  • a common type of dementia in the elderly, affects both neuronal perikarya and synapses within the cerebrum.
• multiple sclerosis (MS)

  • the myelin sheaths surrounding axons are damaged by an autoimmune mechanism that interferes with the activity of the affected neurons and produces various neurologic problems.
• A decrease in the absorption of CSF or a blockage of outflow from the ventricles during fetal or postnatal development results in the condition known as hydrocephalus (Gr. hydro, water + kephale, head), which promotes a progressive enlargement of the head followed by mental impairment
• neuroma

  • newly growing axons may form a swelling
• An excessive accumulation of serous fluid in one or both sides of the scrotal sac, termed a hydrocele, is the most common cause of scrotal swelling and a condition easily corrected surgically
• Cryptorchidism (Gr. kryptos, hidden + orchis, testis), the failure of one or both testes to descend from the abdomen, occurs in about 4% of male neonates, but in most of these individuals, the testes move to the scrotum during the first year. Bilateral cryptorchidism causes infertility if not surgically corrected by 2-3 years of age.
• Both interstitial cell tumors and Sertoli cell tumors are rare. Most (95%) testicular cancer involves germ cell tumors, which only appear after puberty and are much more likely to develop in men with untreated cryptorchidism
• Decreased semen quality, which is frequently idiopathic (arising from unknown causes), is a major cause of male infertility. Common features of poor semen quality include oligospermia (ejaculate volume >2 mL), sperm cell density less than 10-20 million/mL, abnormal sperm morphology, and flagellar defects that impair sperm motility.
• Acute or chronic inflammation of the testis, orchitis, frequently involves the ducts connecting this organ to the epididymis. Common forms of orchitis are produced by infective agents and occur secondarily to a urinary tract infection or a sexually transmitted pathogen such as Chlamydia or Neisseria gonorrhoeae entering the testis from the epididymis or via the lymphatics
• Acute epididymitis is a result of sexually transmitted infections such as gonorrhea or Chlamydia infection and causes intrascrotal pain and tenderness. Persistent inflammation of the epididymis, such as that associated with gonorrhea infections, includes massive invasion by leukocytes into the infected duct, stimulating fibrosis that obstructs the epididymis and is a common cause of male infertility.
• The accessibility of the ductus (vas) deferens in the spermatic cords allows for the most common surgical method of male contraception: vasectomy. In this procedure, a very small incision is made through the scrotal skin near the two ducts and each vas is exposed, cut, and the two ends (or only the end leading to the abdomen) are cauterized and tied.
• After vasectomy sperm are still produced, but they degenerate and are removed by macrophages in the epididymis (and in the scrotal sac if the short portion of the vas is left open-ended.) Inflammatory and other changes occur in the mucosa of the epididymis, but serious adverse effects of vasectomy are usually minimal. A vasectomy may be reversed by surgically reconnecting the two ends of each ductus deferens. However, even successful surgery very often fails to restore fertility, due to incomplete sperm maturation in the epididymis changed by postvasectomy inflammation.
• The prostate gland is prone to three common problems: (1) chronic prostatitis, usually involving bacteria or other infectious agents; (2) nodular hyperplasia or benign prostatic hypertrophy, occurring mainly in the periurethral mucosal glands where it often leads to compression of the urethra and problems with urination; and (3) prostate cancer (adenocarcinoma), the most common cancer in nonsmoking men, occurring mainly in glands of the peripheral zone.
• At the beginning of an erection, acetylcholine from parasympathetic nerves in the penis causes the vascular endothelial cells of the helicine arteries and cavernous tissue to release nitric oxide (NO). Diffusing into the adjacent smooth muscle cells, NO activates guanylate cyclase to produce cyclic GMP, which causes these cells to relax, resulting in increased blood flow, filling of the cavernous spaces, and penile erection.
• Erectile dysfunction, or impotence, can result from diabetes, anxiety, vascular disease, or nerve damage during prostatectomy. The drug sildenafil may alleviate the problem by inhibiting the phosphodiesterase degrading cyclic GMP in the smooth muscle cells of helicine arteries and erectile tissue. The subsequent higher level of cGMP promotes relaxation of these cells and enhances the neural effect to produce or maintain an erection.
• Growing primary follicles can become involved in polycystic ovary syndrome (PCOS) that is characterized by enlarged ovaries with numerous cysts and an anovulatory state (with no follicles completing maturation successfully). The clinical presentation of this disorder is variable and the etiology is unclear, although increased androgen production by the ovaries or adrenals is likely involved. PCOS is a common cause of infertility in women
• Late primary or antral follicles can produce follicular cysts, which are thin-walled, fluid-filled structures with both granulosa and thecal endocrine cells. Follicular cysts are common and usually benign, but can produce high estrogen levels and lead to menstrual irregularities. If cyst formation disrupts blood vessels, blood enters the fluid, often rapidly, and produces a hemorrhagic cyst.
• Tubal ligation is a common surgical type of contraception. The uterine tube mucosa can become inflamed if infectious agents ascend from the lower genital tract, producing a condition named salpingitis after another name for these tubes, the salpinges. Mucosal damage or adhesions caused by chronic salpingitis can lead to infertility or an ectopic (tubal) pregnancy if there is blockage of oocyte or embryo transport to the uterus.
• In tubal pregnancies, the lamina propria may react like the uterine endometrium and form decidual cells. But because of its small diameter and inability to expand, the tube cannot contain the growing embryo and will rupture, causing potentially fatal hemorrhage.
• Viable endometrial cells frequently undergo menstrual reflux into or through the uterine tubes. In some women, this can lead to endometriosis, a disorder with pelvic pain due to endometrial tissue growing on the ovaries, oviducts, or elsewhere. Under the influence of estrogen and progesterone, the ectopic tissue grows and degenerates monthly but cannot be removed effectively from the body. In addition to pain, endometriosis can produce inflammation, ovarian cysts, adhesions, and scar tissue that can cause infertility
• The initial attachment of the embryo usually occurs on the ventral or dorsal walls of the body of the uterus. Sometimes the embryo attaches close to the internal os. In this case, the placenta will be interposed between the fetus and the vagina, obstructing the passage of the fetus at parturition. This situation, called placenta previa, must be recognized by the physician, and the fetus must be delivered by cesarean section. Otherwise, obstructed parturition can lead to death of the fetus.
• Atrophic vaginitis involves thinning or atrophy of the vaginal epithelium caused by diminished estrogen levels and occurs most often in postmenopausal women. This change allows the more frequent inflammation and infections characteristic of this condition. Primary squamous cell carcinoma of the vagina occurs rarely, with most vaginal malignancies having spread secondarily from the cervix or vulva
• When a woman is breastfeeding, the nursing action of the child stimulates tactile receptors in the nipple, resulting in liberation of the posterior pituitary hormone oxytocin. This hormone causes contraction of the smooth muscle of the lactiferous sinuses and ducts, as well as the myoepithelial cells of alveoli and ducts, resulting in the milk-ejection reflex. Negative emotional stimuli, such as frustration, anxiety, or anger, can inhibit the liberation of oxytocin and thus prevent the reflex.
• Breast cancer


  Almost always derived from epithelial cells in the terminal lobules of the glands
• Bacterial infection of a mammary gland, or acute mastitis, may occur in the lactating or involuting breast, usually after obstruction by milk left within small components of the duct system.
• Invasive ductal carcinoma


  The most common form of breast cancer, in which neoplastic cells of intralobular ducts or small branches of lactiferous ducts invade the surrounding stroma, forming a fixed, palpable mass
• Cell spreading (or metastasizing) from the carcinoma

  Via the circulatory or lymphatic vessels to critical organs such as the lungs or brain is responsible for the mortality associated with breast cancer
• Mastectomy treatment


  Axillary lymph nodes are usually also removed surgically and examined histologically for the presence of metastatic mammary carcinoma cells
• Early detection


  • Through self-examination, mammography, ultrasound, and other techniques
  • Has significantly reduced the mortality rate
• Early treatment has significantly reduced the mortality rate
• Cervical cancer


  Cancer of the cervix, the lower, narrow part of the uterus
• The incidence of cervical cancer worldwide has been greatly reduced by widespread, routine screening by exfoliative cytology to examine for dysplasia of the cervical epithelium
• Pap smear


  A test that uses cells that have been lightly scraped from the cervix to detect abnormal cells suggestive of precancerous changes in the epithelium
• The Pap smear was introduced by George Papanicolaou in the 1920s
• Epithelial dysplasia


  Precancerous changes in the epithelium
• Epithelial dysplasia, which precedes squamous cell neoplasia (the most common type of cervical cancer), occurs in metaplastic cells of the transformation zone at a mean age of 54 years