Obesity
Excess body weight to a degree that harms health, defined as a body mass index (BMI) of 30 kg/m² or more. It raises the risk of diabetes, high blood pressure, joint wear and certain cancers.
Observational study
A study in which researchers do not intervene but only observe; it shows associations but not reliable causes.
Obturator artery
A branch of the internal iliac artery that passes through the obturator canal to the adductor muscles of the thigh. An anatomical variant connecting to the inferior epigastric artery (corona mortis) is feared in hernia surgery.
See also: Internal iliac artery, Adductor muscles
Occipital artery
A branch of the external carotid artery running to the back of the head and supplying the scalp and neck muscles. It runs close to the greater occipital nerve.
See also: External carotid artery
Occlusal splint
A custom-made plastic splint worn over one row of teeth at night. It protects the teeth from wear during grinding and can relieve the jaw muscles and joint.
See also: Bruxism
Occupational asthma
Asthma triggered or worsened by substances at work, for example flour dust in bakers or isocyanates. Improvement on days off is an important clue; reporting as an occupational disease is possible.
See also: Bronchial asthma
Occupational medicine
The specialty dealing with the interactions between work and health, such as health checks, workplace safety and occupational diseases.
Olecranon bursa
A bursa just under the skin over the tip of the elbow. It reduces friction and can become inflamed with pressure, injury or infection.
See also: Olecranon bursitis
Olecranon bursitis
Inflammation of the bursa at the tip of the elbow with a firm, elastic swelling, often from frequent leaning. Red, warm swellings may be bacterially infected and then need treatment.
See also: Bursitis
Olfactory bulb
The structure on the underside of the frontal lobe where the fibres of the olfactory cells connect to further nerve cells. Damage, for example after head injuries, can lead to loss of the sense of smell.
Omental bursa (lesser sac)
A space in the abdominal cavity behind the stomach connected to the rest of the cavity by a narrow opening. In pancreatitis, fluid collections can form there.
See also: Peritoneum
Ophthalmic artery
The first major branch of the internal carotid artery, running with the optic nerve into the orbit. Through its branch, the central retinal artery, it supplies the retina.
See also: Internal carotid artery, Optic canal
Ophthalmology
The medical specialty for diseases, injuries and refractive errors of the eye and its surroundings. It covers medical treatment as well as surgery, for example for cataract or retinal detachment.
Orthodontic bracket
A small metal or ceramic attachment bonded to the tooth in fixed braces. Forces are transmitted to the teeth through an inserted archwire.
Osteoarthritis
Wear of the joint cartilage, often in the knees, hips or fingers. Typical features are pain on starting movement, stiffness and reduced mobility.
Out-of-hours medical service
Medical help outside surgery hours for non-life-threatening complaints; in Germany it can be reached on 116117.
Outpatient
Treatment without an overnight hospital stay, for example in a doctor’s practice. The opposite of inpatient.
Ovarian artery
The artery arising directly from the abdominal aorta and running in the suspensory ligament of the ovary to the ovary. It connects with branches of the uterine artery.
See also: Uterine artery
Obturator canal
Short canal at the upper edge of the obturator foramen through which the obturator nerve and vessels pass to the adductor muscles. Rare obturator hernias can emerge here.
Odontogenic sinusitis
Maxillary sinusitis caused by an upper tooth, for example due to apical inflammation or an opening after tooth extraction. It is often one-sided and requires treatment of the tooth.
Odontoid (dens) fracture
Fracture of the tooth-shaped process of the second cervical vertebra, often in older people after a fall. Depending on type and displacement, it is treated with an orthosis or surgically.
See also: Dens (odontoid process), Anderson-D’Alonzo classification
Optic canal
Bony canal in the lesser wing of the sphenoid bone through which the optic nerve and ophthalmic artery pass from the skull into the eye socket. Fractures in this area can damage the optic nerve.
Optic chiasm
Crossing of the optic nerves above the pituitary gland, where fibres from the inner halves of the retinas cross to the opposite side. Pituitary tumours often press here and cause loss of the outer halves of the visual fields.
Optic disc drusen
Calcified deposits in the optic nerve head that make it appear swollen. It is important to distinguish them from papilloedema; rarely, they cause visual field defects.
Organ of Corti
The actual hearing organ in the cochlea of the inner ear, whose hair cells convert sound vibrations into nerve signals. Noise mainly damages the outer hair cells.
Ornate dog tick (Dermacentor reticulatus)
Tick that is spreading increasingly in Germany and is also active in winter. It is best known as a vector of canine babesiosis and can transmit rickettsiae to humans.
See also: Babesiosis