articular head


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head

 [hed]
1. the anterior or superior part of a structure or organism.
2. in vertebrates, the part of the body containing the brain and the organs of special sense. Called also caput.
articular head an eminence on a bone by which it articulates with another bone.
head injury traumatic injury to the head resulting from a fall or violent blow. Such an injury may be open or closed and may involve a brain concussion, skull fracture, or contusions of the brain. All head injuries are potentially dangerous because there can be a slow leakage of blood from damaged blood vessels into or around the brain. Such a process will gradually increase pressure within the skull and compress the surrounding brain (see hematoma).

One of the most common complications of head injury is subdural hematoma, resulting from the oozing of blood from the cortical veins and the small blood vessels that lie between the arachnoid and the dura mater. A less common but more serious complication that constitutes an extreme surgical emergency is epidural hematoma, a collection of blood in the space between the skull and the dura mater. The leaking of blood into the epidural space is the result of the rupture of a large meningeal artery. It progresses rapidly and therefore requires immediate treatment. A third complication that may occur following head injury is herniation of either the brainstem or a part of the cerebellum through the tentorial hiatus (transtentorial herniation). This is an extreme emergency demanding immediate relief of pressure against the blood vessels serving the brain stem and cerebellum.

Long-term effects of head injury include chronic headache, disturbances in mental and motor function, diabetes insipidus, and a host of other symptoms that may or may not be psychogenic. Organic brain damage and posttraumatic epilepsy resulting from scar formation are possible sequels to head injury.
Treatment. The method of treatment will depend on the kind and amount of damage inflicted on the brain and surrounding membranes. Surgical procedures to relieve intracranial pressure include the drilling of burr holes in the skull to aspirate accumulated blood, and intracranial surgery to remove hematomas. Edema of brain tissue may be reduced by the intravenous administration of mannitol. dexamethasone(Decadron), a steroid antiinflammatory agent that has little salt-retaining action, is often used. If no immediate surgery is indicated, the physician may choose to treat the head injury conservatively, with rest and quiet and the careful monitoring of the patient for signs of change in the neurologic status.
Patient Care. Continuous monitoring of the vital signs and assessment of the patient's neurologic status are essential to the care of the patient with a head injury. Fluid intake and output are measured and recorded and are limited according to the degree of edema present. Intravenous fluids must be given with caution and oral liquids allowed as soon as the patient is able to swallow. An excessively large urinary output is reported immediately, as this may indicate damage to the hypothalamus and suppression of antidiuretic hormone.

Any one of the following symptoms should be reported to the physician: (1) changes in the patient's blood pressure, pulse, or respiratory rate, especially slowing of the pulse with a rising blood pressure; (2) extreme restlessness or excitability following a period of comparative calm; (3) changes in the level of consciousness; (4) headache that increases in intensity; (5) vomiting, especially persistent, projectile vomiting; (6) unequal size of pupils; (7) inability to move one of the extremities; (8) leakage of spinal fluid (clear yellow or pink-tinged) from the nose or ear.

When leakage of spinal fluid is suspected, this can be verified by using a Clinistix test for sugar. If it is positive, the leaking fluid is spinal fluid rather than mucus. When there is leakage of spinal fluid through the nose, the patient must be warned not to blow the nose. Leakage of spinal fluid from the nose or the ear demands absolute bed rest with the head elevated 30 degrees to maintain neutral intracranial pressure and promote healing.

Patients who are unconscious must be watched closely for respiratory difficulty or inability to swallow. If the patient cannot swallow, the head must be turned to the side and the mouth and trachea suctioned as necessary to prevent aspiration of mucus into the lungs. A tracheostomy set and ventilator should be readily at hand in case severe respiratory embarrassment occurs.

Side rails are applied and the headboard of the bed is padded with pillows or a blanket if the patient is delirious or if convulsions are anticipated. An accurate record of the patient's intake and output is kept and the patient is observed for signs of retention of urine, incontinence, or abdominal distention.
Some mechanisms of head injury. Head injury results from penetration or impact. A, A direct injury (blow to skull) may fracture the skull. Contusion and laceration of the brain may result from fractures. Depressed portions of the skull may compress or penetrate brain tissue. B, In the absence of skull fracture, a blow to the skull may cause the brain to move enough to tear some of the veins going from the cortical surface to the dura. Subsequently, subdural hematoma may develop. Note the areas of cerebral contusion (shaded in red). C, Rebound of the cranial contents may result in an area of injury opposite the point of impact. Such an injury is called a contrecoup injury. In addition to the three injuries depicted, secondary phenomena may result from the injury and cause additional brain dysfunction or damage. For example, ischemia, especially cerebral edema, may occur, elevating intracranial pressure. From Polaski and Tatro, 1996.
sperm head (head of spermatozoon) the oval anterior end of a spermatozoon, which contains the male pronucleus and is surrounded by the acrosome. See illustration at spermatozoon.

articular head

[TA]
generic term for the rounded articulating surface of a long bone or process received by an articular fossa.
Synonym(s): caput articulare [TA]

articular head

a projection on a bone that forms a joint with another bone.

head

1. the anterior or superior part of a structure or organism, in vertebrates containing the brain and the organs of special sense. See also skull, caput.
2. one animal; used in reference to farm livestock, e.g. ten head of cattle.

articular head
an eminence on a bone by which it articulates with another bone.
head bail
head bob
the patient is unable to keep the head still while at rest, it makes an involuntary, usually at regular intervals, short, quick downward movement then recovers.
head bot
head cap
of spermatozoon, formed by the collapse of the acrosomial vesicle over the nucleus.
head carriage
includes at attention, drooping, rotated, deviated.
head catarrh
malignant catarrhal fever.
head clamp
head collar
a leather halter-like piece of harness consisting of a poll strap, nose band and usually a rope shank.
head cover
hood or cap used by surgical personnel to reduce contamination of the surgical area by hair and associated flora.
head deviation
the poll-nose axis is turned laterally so that the animal walks in circles but there is no disturbance of balance. Occurs in lesions of the neck and of the cerebral cortex.
fetal head lateral deviation
the fetal head is deviated laterally to lie against the shoulder of the fetus, the front feet and the lateral aspect of the neck being presented to the pelvic inlet; a dystocia which can only be relieved by repulsion of the fetus and the return of the head to between the front feet.
fetal head ventral deviation
the head of the fetus is flexed ventrally so that the fore feet and the dorsum of the neck are presented to the pelvic inlet; a dystocia which can only be relieved by repulsion of the fetus and lifting of the head into the pelvic canal.
head grit
jaundice, photosensitization and hepatic injury in lambs caused by Narthecium ossifragum poisoning.
head injury
traumatic injury to the head resulting from a fall or violent blow. Such an injury may be open or closed and may involve a brain concussion, skull fracture, or contusions of the brain.
head mange
nerve head
the optic disk.
head nod
see head bob (above).
head picking
a form of cannibalism in which birds pick at and injure each other's wattles, combs, eyes; beak trimming reduces the problem but does not prevent the vice.
head posture
see head carriage (above).
head pressing
persistent pushing with the head against a fixed object. Part of the dummy syndrome as in hepatic encephalopathy or encephalitis.
head process
the elongating cephalic tissues which represent the first step in the development of the fetal body.
head rotation
twisting of the head around the axis from the poll to the nose. To be differentiated from deviation of the head. Caused usually by lesions of the vestibular apparatus on one side. The animal walks in circles and has problems maintaining its balance.
head shaking
common in dogs and cats with acute inflammation or foreign bodies in the external ear canal. May be a cause of auricular hematoma. Seasonal head shaking is seen in horses mainly during spring, worsening in summer. A trigeminal neuritis caused by increased levels of melatonin is the suspected cause in some. Allergic rhinitis may also be an underlying cause.
head shy
said of a horse that tries to avoid having its head handled or its headstall put on.
head stall
see head collar (above).
head tilt
includes rotation and deviation.
Enlarge picture
Head tilt. By permission from Nelson RW, Couto CG, Small Animal Internal Medicine, Mosby, 2003
head tremor
a feature of cerebellar lesions.
head twist injury
injury to cervical vertebrae may occur in horses as a result of a fall with the head and neck under the body.
head's zones
in acupuncture the zones of human skin which are responsive to abnormalities in each of the vital organs.