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 [fos´ah] (pl. fos´sae) (L.)
a trench or channel; in anatomy, a hollow or depressed area.
amygdaloid fossa the depression in which the tonsil is lodged.
cerebral fossa any of the depressions on the floor of the cranial cavity.
condylar fossa (condyloid fossa) either of two pits on the lateral portion of the occipital bone.
coronoid fossa a depression in the humerus for the coronoid process of the ulna.
cranial fossa any one of the three hollows (anterior, middle, and posterior) in the base of the cranium for the lobes of the brain.
digastric fossa a depression on the inner surface of the mandible, giving attachment to the anterior belly of the digastric muscle.
epigastric fossa
1. one in the epigastric region.
ethmoid fossa the groove in the cribriform plate of the ethmoid bones, for the olfactory bulb.
glenoid fossa mandibular fossa.
hyaloid fossa a depression in the front of the vitreous body, lodging the lens.
hypophyseal fossa a depression in the sphenoid lodging the pituitary gland; called also pituitary fossa.
iliac fossa a concave area occupying much of the inner surface of the ala of the ilium, especially anteriorly; from it arises the iliac muscle.
incisive fossa a slight depression on the anterior surface of the maxilla above the incisor teeth.
infraclavicular fossa the triangular region of the chest just below the clavicle, between the deltoid and pectoralis major muscles.
infratemporal fossa an irregularly shaped cavity medial or deep to the zygomatic arch.
interpeduncular fossa a depression on the inferior surface of the midbrain, between the two cerebral peduncles, the floor of which is the posterior perforated substance.
ischiorectal fossa a potential space between the pelvic diaphragm and the skin below it; an anterior recess extends a variable distance.
mandibular fossa a depression in the inferior surface of the pars squamosa of the temporal bone at the base of the zygomatic process, in which the condyle of the mandible rests; called also glenoid fossa.
mastoid fossa a small triangular area between the posterior wall of the external acoustic meatus and the posterior root of the zygomatic process of the temporal bone.
nasal fossa the portion of the nasal cavity anterior to the middle meatus.
navicular fossa
1. the lateral expansion of the urethra of the glans penis.
2. a depression on the internal pterygoid process of the sphenoid, giving attachment to the tensor veli palatini muscle.
fossa ova´lis cor´dis a fossa in the right atrium of the heart; the remains of the fetal foramen ovale.
fossa ova´lis fe´moris the depression in the fascia lata that is bridged by the cribriform fascia and perforated by the great saphenous vein.
ovarian fossa a shallow pouch on the posterior surface of the broad ligament of the uterus in which the ovary is located.
paravesical fossa the fossa formed by the peritoneum on each side of the urinary bladder.
pituitary fossa hypophyseal fossa.
popliteal fossa the hollow at the posterior part of the knee.
subarcuate fossa a depression in the posterior inner surface of the pars petrosa of the temporal bone.
subpyramidal fossa a depression on the internal wall of the middle ear.
subsigmoid fossa a fossa between the mesentery of the sigmoid flexure and that of the descending colon.
supraspinous fossa a depression above the spine of the scapula.
temporal fossa an area on the side of the cranium bounded posteriorly and superiorly by the temporal lines, anteriorly by the frontal and zygomatic bones, and laterally by the zygomatic arch, lodging the temporal muscle.
tibiofemoral fossa a space between the articular surfaces of the tibia and femur mesial or lateral to the inferior pole of the patella.
urachal fossa one on the inner abdominal wall, between the urachus and the hypogastric artery.
vestibular fossa (fossa of vestibule of vagina) the vaginal vestibule between the vaginal orifice and the fourchette (frenulum of pudendal labia). Called also navicular fossa.


[fos′ə] pl. fossae
Etymology: L, ditch
a hollow or depression, especially on the surface of the end of a bone, such as the olecranon fossa or the coronoid fossa.


Plural of fossa, see there.


(fos'a) plural.fossae [L. fossa, ditch]
A furrow, recess, or shallow depression.

acetabular fossa

The rough-surfaced depression in the center of the acetabulum (femoral socket) of the hipbone. The fossa is deeper than the actual joint articulation and does not directly contact the head of the femur.

antecubital fossa

The triangular region in the forearm on the anterior (flexor) surface of the elbow. Bounded laterally by the brachioradialis muscle and medially by the pronator teres muscle, the fossa contains the tendon of the biceps brachialis muscle and the brachial artery. Two large superficial veins, the cephalic and its branch, the median cubital, are common sites for blood drawing. Synonym: cubital fossa

anterior cranial fossa

The anterior one-third of the floor of the cranial cavity; the fossa is formed from the orbital part of the frontal bones, the cribriform plates of the ethmoid bone, and one third of the anterior sphenoid bones (the anterior body and lesser wings). The olfactory lobes and the inferior surfaces of the cerebral hemispheres lie in this fossa.

articular fossa of mandible

Mandibular fossa.

articular fossa of temporal bone

Mandibular fossa

axillary fossa

The armpit; axilla.

canine fossa

On the skull, the vertical furrow along the surface of the maxilla beginning between the upper canine tooth and the first premolar tooth and extending up toward the orbit.

central fossa of tooth

The front-to-back (anterior-posterior) midline groove along the upper (occlusal) surface of a postcanine tooth.
See: central fissure

cerebral fossa

Cranial fossa.

Claudius fossa

See: Claudius fossa

condylar fossaof occipital bone

On the base of the occipital bone of the skull along the lateral edge of the foramen magnum, a prominent depression behind the occipital epicondyle.

coronoid fossa

On the anterior surface of the lower end of the humerus, a depression proximal to the trochlea and between the lateral and medial epicondyles; it is analogous to the olecranon fossa on the opposite side of the humerus. During full flexion of the forearm, the coronoid process of the ulna fits into the coronoid fossa of the humerus.

cranial fossa

One of the three floor "levels" (anterior, middle, and posterior cranial fossae) of the interior surface of the cranial cavity. Each level contains the impressions of surface features of corresponding brain regions. Synonym: cerebral fossa; hypophyseal fossa

cubital fossa

Antecubital fossa.

digastric fossa

A small depression in the mandible behind its lower margin at either side of the midline (symphysis menti). The anterior belly of the digastric muscle attaches in this fossa.

epigastric fossa

The pit of the inside of the stomach.

ethmoid fossa

Olfactory groove.

glenoid fossa

1. The shallow ovoid depression on the top of the lateral side of the scapula that articulates with the head of the humerus. The acromion of the scapula overhangs the glenoid fossa. Synonym: glenoid cavity
2. Mandibular fossa.

hyaloid fossa

The depression on the anterior surface of the vitreous body of the eye. The lens is located there.

hypophyseal fossa

Cranial fossa.

iliac fossa

On each hip bone, the smooth, concave upper surface of the ilium, which makes a shelf that gently slopes downward and inward from the iliac crest.

implantation fossa of sperm

On a spermatozoon, the small segment behind the head to which the internal filaments of the tail attach.

incisive fossa

The vertical furrow along the surface of the maxilla beginning between the lateral upper incisor and the canine tooth and extending up toward the anterior nasal aperture.

fossa incudis

In the tympanic cavity of the middle ear, a small depression inside the epitympanic recess, in which the short process of the incus fits and is attached by tiny ligaments.

infraspinous fossa

On the dorsal (posterior) surface of the scapula, the broad, shallow, triangular-shaped depression filling the area below the scapular spine. The infraspinatus muscle is attached to and covers most of this fossa.

infratemporal fossa

On the lateral surface of the skull, an irregular pocket formed largely by the concave outer surface of the greater wing of the sphenoid bone as it curves into the lateral pterygoid plate of the sphenoid. This fossa is deep (medial) to the zygomatic arch and is continuous with the bottoms of both the temporal fossa and the inferior orbital fissure. The medial wall of the infratemporal fossa is split vertically by the pterygomaxillary fissure, which leads into the pterygopalatine fossa.

inguinal fossa

One of two vertical valleys in the peritoneum along each side of the anterior abdominal wall. The medial inguinal fossa is the depression between the medial and lateral umbilical folds; direct inguinal hernias typically protrude through the abdominal wall in the lower end of this fossa. The lateral inguinal fossa is the depression lateral to the lateral umbilical fold; the lower end of this fossa becomes the deep inguinal ring, the internal end of the inguinal canal.

intercondyloid fossa

The depression on the inferior surface of the femur between the femoral condyles. The cruciate ligaments pass through it.

interpeduncular fossa

On the anterior (ventral) surface of the midbrain, a trapezoidal depression behind the mammillary bodies and between the cerebral peduncles. The oculomotor nerve (CN III) leaves the midbrain through this fossa, and a number of separate branches of the posterior cerebral arteries enter the midbrain through the base of the fossa, in an area called the perforated substance.

ischioanal fossa

Ischiorectal fossa.

ischiorectal fossa

A wedge-shaped region just under the skin on either side of the lower end of the rectum and anal canal. The fossa is bounded laterally by the obturator internus muscle and the tuberosity of the ischium, medially by the levator ani and coccygeus muscles, and posteriorly by the gluteus maximus muscle. The ischiorectal fossa contains fat, connective tissue, blood vessels, and nerves.
Synonym: ischioanal fossa

jugular fossa

On the base of the skull, a kidney bean-shaped depression in the undersurface of petrous portion of the temporal bone. The fossa is behind the carotid canal, from which it is separated by a ridge of bone, and it forms a pocket for the superior bulb of the jugular vein, just after the vein has exited the skull through the jugular foramen.

lacrimal fossa

A shallow depression in the lateral side of the roof of the orbit, just inside the upper orbital margin, into which the lacrimal gland fits.

lenticular fossa

The depression in the anterior surface of the vitreous for reception of the crystalline lens.

mandibular fossa

In the skull, the depression in the temporal bone into which the condyle of the head (condylar process) of the mandible fits; the condyle of the mandible sits on an interposed articular disc when the mandible is fully elevated (teeth clenched). The fossa, a part of the temporomandibular joint, is a horizontal furrow lying underneath and behind the zygomatic process of the temporal bone. Synonym: articular fossa of mandible; glenoid fossa (2)

mastoid fossa

The small triangular area between the posterior wall of the acoustic meatus and the posterior root of the zygomatic process of the temporal bone.

middle cranial fossa

The middle one-third of the floor of the cranial cavity; it is deeper and wider than the anterior cranial fossa. The middle cranial fossa is formed from the posterior two thirds of the sphenoid bones (the greater wings, the dorsum sella, and the clinoid processes) and the petrous and squamous portions of the temporal bones. The middle cranial fossa contains the superior orbital fissures, optic canals, foramina rotundum, foramina ovale, foramina spinosum, and foramina lacerum. The temporal lobes of the cerebral hemispheres, the optic chiasm, the hypophysis (pituitary), internal carotid arteries, circle of Willis, and cavernous sinuses lie in the middle cranial fossa.

nasal fossa

The cavity between the anterior opening to the nose and the nasopharynx.

navicular fossa

In the female perineum, the recess at the posterior end of the vaginal vestibule. This fossa is posterior to the vaginal opening and anterior to the fourchette, i.e., the frenulum, where the labia minora join posteriorly. Synonym: fossa of the vaginal vestibule

olecranon fossa

On the posterior surface of the lower end of the humerus, a depression proximal to the trochlea and between the medial and lateral epicondyles; it is analogous to the coronoid fossa on the opposite side of the humerus. During full extension of the forearm, the olecranon process of the ulna fits into the olecranon fossa of the humerus

fossa ovalis of heart

An oval depression in the septal wall of the right atrium; it has a raised rim along its top and front edges. In the embryo, the floor of the fossa ovalis is a flap valve (the primary atrial septum or septum primum) that lets blood flow from the right atrium to the left atrium, bypassing the lungs. If the flap valve fails to seal after birth, the heart can have an atrial septal defect.

fossa ovalis cordis

The remnant of the embryonic foramen ovale in the right cardiac atrium.

ovarian fossa

A shallow depression in the wall of the pelvis behind the lateral ends of the broad ligament; the ovary lies in this fossa covered by the parietal peritoneum.

piriform fossae

Any of the depressions in the lateral walls of the laryngopharynx.

pituitary fossa

Sella turcica.

popliteal fossa

A rhomboid space, just below the skin, behind the knee. Its edges are defined by muscles — laterally, the biceps femoris and the lateral head of the gastrocnemius; medially, the semitendinosus, the semimembranosus, and the medial head of the gastrocnemius. This fossa contains the popliteal vessels and the tibial and common fibular nerves.

posterior cranial fossa

The posterior third of the floor of the cranial cavity; it is larger and deeper than the anterior and middle cranial fossae. The posterior cranial fossa is formed from the posterior surface of the body of the sphenoid bone (the dorsum sella), the posterior surfaces of the petrous and mastoid portions of the temporal bones, and the inner surfaces of the occipital bones. The posterior cranial fossa contains the internal auditory canals, the foramen magnum, and the jugular foramina. The brainstem, the cerebellum, and the transverse and sigmoid sinuses lie in the posterior cranial fossa.

pterygoid fossa

The vertical trough between the medial and lateral pterygoid plates of the pterygoid process of the sphenoid bone. This fossa is on the deep, basal surface of the skull, just outside (lateral to) the nasopharynx.

pterygopalatine fossa

A thin wedge-shaped space behind the nasal cavity and below the deep apex of the orbit; laterally, it opens into the infratemporal fossa (via the pterygomaxillary fissure). The pterygopalatine fossa contains the pterygopalatine ganglion. The maxillary branch of the trigeminal nerve (CN V) enters the fossa from behind, through the foramen rotundum, and the pterygoid nerve enters the fossa via the pterygoid canal.
Synonym: sphenomaxillary fossa

radial fossa of humerus

A small depression in the distal humerus on its anterior surface proximal to the capitulum. When the elbow is in complete flexion, the proximal end (the head) of the radius slides up along the capitulum and one edge of the head of the radius fits into the radial fossa.

rhomboid fossa

In the brainstem, the floor of the fourth ventricle, which runs along the dorsal surface of the pons and part of the medulla.

Rosenmüller fossa

See: Rosenmüller, Johann Christian

scaphoid fossaof auricle (pinna)

In the auricle of the ear, the C-shaped groove between the helix and the antihelix.

sphenomaxillary fossa

Pterygopalatine fossa.

subarcuate fossa

In the posterior cranial fossa, a variably shaped small depression in the petrous portion of the tympanic bone superior and lateral to the internal acoustic foramen. The subarcuate fossa leads into the subarcuate canal, which contains the subarcuate artery, a main blood supplier to the bony labyrinth, facial canal, and mucosa of the mastoid antrum.

sublingual fossa

A shallow depression on the inner surface of the body of the mandible above the anterior part of the mylohyoid ridge. It is occupied by the major salivary gland in the area, the sublingual gland.

submandibular fossa

An oblong depression between the mylohyoid ridge and the inferior border of the medial surface of the body of the mandible. It is occupied by the submandibular gland. These were previously referred to as the submaxillary fossa and submaxillary gland.

subpyramidal fossa

A depression in the inferior wall of the middle ear. It is inferior to the round window and posterior to the pyramid.

supraclavicular fossa

The depression that can be felt below the skin at the base of the neck behind the clavicle and extending from the attachment of the sternal head of the sternocleidomastoid muscle medially to the medial edge of the deltoid muscle laterally.

supraspinous fossa

The sloping, triangular concave surface above the spine on the dorsal (posterior) side of the scapula. The supraspinatus muscle attaches to and fills most of this fossa.

fossa supratonsillaris

The space between the anterior and posterior pillars of the fauces above the tonsil.

supratonsillar fossa

A slit-like recess extending into the upper part of the palatine tonsil. This fossa is a remnant of the embryological second pharyngeal pouch. Synonym: intratonsillar cleft

supravesical fossa

On the internal surface of the anterior abdominal wall, a depression in the parietal peritoneum between the middle (median) and medial umbilical folds.

temporal fossa

On the side of the skull, a large fan-shaped depression containing the temporalis muscle. The fossa's upper edge forms a broad crescent (the temporal lines) along the frontal, parietal, and temporal bones, from the upper outer edge of the orbit to the most posterior edge of the zygomatic arch. From the crescent, the fossa gradually deepens toward the "handle" of the fan, which lies inside the zygomatic arch.

tonsillar fossa

A valley between the glossopalatine and pharyngopalatine arches along the lateral wall of the oropharynx and containing the palatine tonsil. Synonym: tonsillar recess.

trochanteric fossa

At the proximal end of the femur, an irregular recess along the upper inner (proximal medial) surface of the great trochanter, where the medial edge of the greater trochanter overhangs the neck of the femur.

fossa of the vaginal vestibule

Navicular fossa.
References in periodicals archive ?
While some scientists have proposed that the Medusae Fossae sediments are composed of volcanic ash, others have suggested that they are ancient accumulations of windblown dust.
The external genitalia and the urogenital diaphragm are found within the urogenital triangle, while the anal triangle is composed of the centrally placed anal canal encircled by the external anal sphincter and flanked laterally and posteriorly by the ischiorectal fossae (Figure 3).
Posteriorly the ischiorectal fossae extends below the lower edge of gluteus maximus as far as the sacrotuberous ligament (Figure 4).
The ischiorectal fossae are filled with adipose tissue that is infiltrated with numerous tough, fibrous bands and septa, some of which are derived from the longitudinal muscle of the anal canal (Figure 4).
Physical examination revealed a pink mass with bulging contours filling the right nasal fossae (figure 3).
Three years after the last surgery, the nasal fossae are flee of any mass and the patient remains asymptomatic.
Adrian Brown, corresponding author, explains, "We suggest that the associated hydrothermal activity would have provided sufficient energy for biological activity on early Mars at Nili Fossae.
The upper portion of the image swath shows the eastern margin of Kasei Valles and the western margin of the Lunae Planum plateau and the adjoining Sacra Fossae.
Sacra Fossae is a fault system that extends for more than 1000 km.