sheath


Also found in: Dictionary, Thesaurus, Legal, Encyclopedia, Wikipedia.
Related to sheath: cable sheath, carotid sheath

sheath

 [shēth]
a tubular case or envelope.
arachnoid sheath the delicate membrane between the pial sheath and the dural sheath of the optic nerve.
carotid sheath a portion of the cervical fascia enclosing the carotid artery, internal jugular vein, vagus nerve, and sympathetic nerves supplying the head.
connective tissue sheath of Key and Retzius endoneurium.
crural sheath femoral sheath.
dural sheath the external investment of the optic nerve.
femoral sheath the fascial sheath of the femoral vessels.
Henle's sheath endoneurium.
lamellar sheath the perineurium.
medullary sheath myelin sheath.
myelin sheath (nerve sheath) the sheath surrounding the axon of myelinated nerve cells, consisting of concentric layers of myelin formed in the peripheral nervous system by the plasma membrane of Schwann cells, and in the central nervous system by the plasma membrane of oligodendrocytes. It is interrupted at intervals along the length of the axon by gaps known as nodes of Ranvier. Myelin is an electrical insulator that serves to speed the conduction of nerve impulses (see saltatory conduction).
pial sheath the innermost of the three sheaths of the optic nerve.
root sheath the epidermic layer of a hair follicle.
sheath of Schwann neurilemma.
synovial sheath synovial membrane lining the cavity of a bone through which a tendon moves.
tendon sheath a lubricated fibrous or synovial layer of tissue in which the tendon is housed and through which it moves.

sheath

(shēth),
1. Any enveloping structure, such as the membranous covering of a muscle, nerve, or blood vessel. Any sheathlike structure. Synonym(s): vagina (1)
2. The prepuce of male animals, especially of the horse.
3. A specially designed tubular instrument through which special obturators or cutting instruments can be passed, or through which blood clots, tissue fragments, and calculi can be evacuated.
4. A tube used as an orthodontic appliance, usually on molars.
[A.S. scaeth]

sheath

(shēth) a tubular case or envelope.
arachnoid sheath  the continuation of the arachnoidea mater around the optic nerve, forming part of its internal sheath.
carotid sheath  a portion of the cervical fascia enclosing the carotid artery, the internal jugular vein, and the vagus nerve.
crural sheath  femoral s.
dentinal sheath  the layer of tissue forming the wall of a dentinal tubule.
dural sheath  the external investment of the optic nerve.
femoral sheath  the investing fascia of the proximal portion of the femoral vessels.
sheath of Henle  endoneurium.
Hertwig sheath  root s. (1).
sheath of Key and Retzius  endoneurium.
lamellar sheath  the perineurium.
Mauthner's sheath  axolemma.
medullary sheath , myelin sheath the sheath surrounding the axon of myelinated nerve cells, consisting of concentric layers of myelin formed in the peripheral nervous system by the plasma membrane of Schwann cells, and in the central nervous system by oligodendrocytes. It is interrupted at intervals along the length of the axon by gaps known as nodes of Ranvier. Myelin is an electrical insulator that serves to speed the conduction of nerve impulses.
pial sheath  the continuation of the pia mater around the optic nerve, forming part of its internal sheath.
root sheath 
1. an investment of epithelial cells around the unerupted tooth and inside the dental follicle.
2. the epithelial portion of a hair follicle.
sheath of Schwann  neurilemma.
synovial sheath  synovial membrane lining the cavity of a bone through which a tendon moves.
tendon sheath  epitendineum.

sheath

(shēth)
n. pl. sheaths (shēthz, shēths)
An enveloping tubular structure, such as the tissue that encloses a muscle or nerve fiber.

sheath

[shēth]
Etymology: AS, scaeth
a tubular structure that surrounds an organ or any other part of the body, such as the sheath of the rectus abdominis muscle or the sheath of Schwann, which covers various nerve fibers.

sheath

(shēth)
1. Any enveloping structure, such as the membranous covering of a muscle, nerve, or blood vessel; any sheathlike structure.
Synonym(s): vagina (1) .
2. The prepuce of male animals, especially of the horse.
3. A specially designed tubular instrument through which special obturators or cutting instruments can be passed, or through which blood clots, tissue fragments, or calculi can be evacuated.
4. A tube used as an orthodontic appliance, usually on molars.
[A.S. scaeth]

sheath

(sheth)
1. A covering structure of connective tissue, usually of an elongated part, such as the membrane covering a muscle.
2. An instrument introduced into a vessel during angiographic procedures when multiple catheter changes are anticipated. It facilitates ease of change and decreases morbidity at the puncture site.

Patient care

The sheath introduced into the femoral artery, the preferred vascular access route for percutaneous coronary intervention, is a 4 to 6 French (1.35 to 2 mm) in size. The sheath remains in place after completion of the procedure and removal of the catheter until anticoagulation is reversed or anticoagulants are below peak action. The sheath is connected to high-pressure tubing and a flushing system; manual or automatic flushing keeps the line patent. A stopcock connected to the system permits drawing of blood samples.

axon sheath

A myelin sheath or a neurilemma.
See: myelin sheath

carotid sheath

The portion of cervical or pretracheal fascia enclosing the carotid artery, interior jugular vein, and vagus nerve.

crural sheath

The fascial covering of femoral vessels.

dural sheath

A fibrous membrane or external investment of the optic nerve.

femoral sheath

The fascia covering the femoral vessels.

sheath of Henle

See: Henle sheath

sheath of Hertwig

See: Hertwig's root sheath

sheath of Key and Retzius

Endoneurium.

lamellar sheath

A connective tissue sheath covering a bundle of nerve fibers. Synonym: nerve sheath; perineurium

medullary sheath

An obsolete term for myelin sheath.
Enlarge picture
MYELIN SHEATH

myelin sheath

Layers of the cell membrane of Schwann cells (peripheral nervous system) or oligodendrocytes (central nervous system) that wrap nerve fibers, providing electrical insulation and increasing the velocity of impulse transmission.
Synonym: Schwann sheath See: nerve fiber; neuron; illustration

nerve sheath

Lamellar sheath.

periarterial lymphoid sheath

The tissue composed of T lymphocytes that surrounds each arteriole in the spleen. The sheaths are attached to lymphoid follicles containing B cells and make up much of the white pulp. See: spleen

pial sheath

An extension of the pia that closely invests the surface of the optic nerve.

sheath of Schweigger-Seidel

The thickened wall of a sheathed artery of the spleen.

rectus sheath

A strong fibrous sleeve in which the rectus abdominis and pyramidalis muscles contract. The sheath is formed from the aponeuroses of the abdominal wall muscles as they meet in the linea alba at the abdominal midline.

root sheath

1. One of the layers of a hair follicle derived from the epidermis. It includes the outer root sheath, which is a continuation of the stratum germinativum, and the inner root sheath, which consists of three layers of cells that closely invest the root of the hair. See: hair
2. The epithelial covering that induces root formation in teeth. Also called Hertwig's root sheath.

synovial sheath

Synovial tendon sheath.

tendon sheath

A dense fibrous sheath that confines a tendon to an osseous groove, converting it into an osteofibrous canal. It is found principally in the wrist and ankle.
See: synovial sheath

sheath

1. An enveloping structure or part, usually tubular.
2. A condom.

sheath

(shēth)
1. Tube used as an orthodontic appliance, usually on molars.
2. Any enveloping structure, such as membranous covering of a muscle, nerve, or blood vessel.
3. Specially designed tubular instrument through which special obturators or cutting instruments can be passed, or through which blood clots, tissue fragments, and calculi can be evacuated.
[A.S. scaeth]

sheath

1. a tubular case or envelope.
2. vernacular for prepuce.

adrenal pericapsular sheath
contains a plexus of large nerve trunks with numerous ganglion cells.
arachnoid sheath
the delicate membrane between the pial sheath and the dural sheath of the optic nerve.
carotid sheath
a portion of the cervical fascia enclosing the carotid artery, internal jugular vein, and vagus or vagosympathetic nerve.
carpal tendon s's
sheaths to the tendons of the muscles which course over the carpus.
crural sheath
femoral sheath.
dural sheath
the external investment of the optic nerve.
femoral sheath
the fascial sheath of the femoral vessels.
Henle's sheath
the endoneurium, especially the delicate continuation around the terminal branches of nerve fibers.
lamellar sheath
the perineurium.
medullary sheath, myelin sheath
the sheath surrounding the axon of myelinated nerve cells, consisting of concentric layers of myelin formed in the peripheral nervous system by the plasma membrane of Schwann cells, and in the central nervous system by the plasma membrane of oligodendrocytes. It is interrupted at intervals along the length of the axon by gaps known as nodes of Ranvier. Myelin is an electrical insulator that serves to speed the conduction of nerve impulses.
pial sheath
the innermost of the three sheaths of the optic nerve.
root sheath
the epidermal layer of a hair follicle.
sheath of Schwann
neurilemma.
synovial sheath
a synovial membrane sleeve through which a tendon moves; found commonly where a tendon passes over a joint.
References in classic literature ?
And let me see, now, whether you can draw it out of the sheath without hurting yourself.
We sold the carved sheaths of our krisses--the ivory sheaths with golden ferules.
5 Core X 300 Sqmm, Pvc Stranded Aluminum Sector Shaped Conductor, Heat Resistant Type "C" Pvc Insulation Suitable For Maximum Continuous Conductor Operating Temperature Of 85 Degree Celcious Confirming To Requirements Of Is:5831-Latest, Extruded Pvc Inner Sheath, Galvanished Steel Strip Armoured, Frls (C2 Type) And St2 Pvc Outer Sheath Overall Confirming To Is: 1554 (Part-1) Latest, Other Details As Per Annexure I Qty: 1000 Mr 2)1.
8, 2014 /PRNewswire/ -- Kalila Medical, a privately held medical device company focused on the development of next-generation steerable catheter technologies, today announced it has received CE mark approval for its Vado(TM) Steerable Introducer Sheath for vascular and intracardiac access including Atrial Fibrillation (AF) procedures.
The sheath is made of 100% I'm green PE from Braskem of Brazil (U.
The sheath will he released internationally "soon," according to the company.
The three scissors in the brass sheath are a rather motley assortment coming from Sheffield, France and Germany - Germany becoming the principal manufacturer of scissors in the early 20th century.
On a recent vacation, I found this beautiful knife sheath at the Custer Battlefield Trading Post (CBTP) at Crow Agency, Montana.
In 1564, an Italian anatomist claimed to have invented a linen sheath which, when dipped in a solution of salt or herbs, formed a protection against syphilis.
Although many complications regarding PAC are recognised, immobilisation of the PAC by invagination of the percutaneous introducer sheath has not been reported previously.
A sheathed thermocouple typically comprises a metal sheath with thermocouple elements inside that are tightly packed with mineral powder.