mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

ian anatomy, the cribriform plate (

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

for lit. ''

sieve A sieve (), fine mesh strainer, or sift is a tool used for separating wanted elements from unwanted material or for controlling the particle size distribution of a sample, using a screen such as a woven mesh or net or perforated sheet m ...

-shaped''), horizontal lamina or lamina cribrosa is part of the

ethmoid bone The ethmoid bone (; from ) is an unpaired bone in the skull that separates the nasal cavity from the brain. It is located at the roof of the nose, between the two orbits. The cubical (cube-shaped) bone is lightweight due to a spongy constructi ...

. It is received into the

ethmoidal notch The ethmoidal notch separates the two orbital plates; it is quadrilateral, and filled, in the articulated skull, by the cribriform plate of the ethmoid. The margins of the notch present several half-cells which, when united with corresponding ha ...

of the

frontal bone In the human skull, the frontal bone or sincipital bone is an unpaired bone which consists of two portions.'' Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bo ...

and roofs in the

nasal cavities The nasal cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nasal c ...

. It supports the

olfactory bulb The olfactory bulb (Latin: ''bulbus olfactorius'') is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OF ...

, and is perforated by

olfactory foramina The olfactory foramina, also known as the cribriform foramina (cribr- is "a sieve" in Greek), is the grouping of holes located on the cribriform plate. The cribriform plate forms the roof of the nasal cavity, and the olfactory foramina are in the ...

for the passage of the

olfactory nerve The olfactory nerve, also known as the first cranial nerve, cranial nerve I, or simply CN I, is a cranial nerve that contains sensory nerve fibers relating to the sense of smell. The afferent nerve fibers of the olfactory receptor neurons t ...

s to the roof of the

nasal cavity The nasal cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nas ...

to convey smell to the brain. The foramina at the

medial Medial may refer to: Mathematics * Medial magma, a mathematical identity in algebra Geometry * Medial axis, in geometry the set of all points having more than one closest point on an object's boundary * Medial graph, another graph that repr ...

part of the groove allow the passage of the nerves to the upper part of the

nasal septum The nasal septum () separates the left and right airways of the Human nose, nasal cavity, dividing the two nostrils. It is Depression (kinesiology), depressed by the depressor septi nasi muscle. Structure The fleshy external end of the nasal s ...

while the foramina at the lateral part transmit the nerves to the

superior nasal concha The superior nasal concha is a small, curved plate of bone representing a medial bony process of the labyrinth of the ethmoid bone. The superior nasal concha forms the roof of the superior nasal meatus. Anatomy Anatomical relations The super ...

. A fractured cribriform plate can result in

olfactory dysfunction The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, it ...

, septal hematoma,

cerebrospinal fluid rhinorrhoea Cerebrospinal fluid rhinorrhoea (CSF rhinorrhoea) refers to the drainage of cerebrospinal fluid through the Human nose, nose (Rhinorrhea, rhinorrhoea). It is typically caused by a basilar skull fracture, which presents complications such as infect ...

(CSF rhinorrhoea), and possibly infection which can lead to

meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, intense headache, vomiting and neck stiffness and occasion ...

. CSF rhinorrhoea (clear fluid leaking from the nose) is very serious and considered a

medical emergency A medical emergency is an acute injury or illness that poses an immediate risk to a person's life or long-term health, sometimes referred to as a situation risking "life or limb". These emergencies may require assistance from another, qualified ...

. Aging can cause the openings in the cribriform plate to close, pinching olfactory nerve fibers. A reduction in olfactory receptors, loss of blood flow, and thick nasal mucus can also cause an impaired sense of smell.

Structure

The cribriform plate is part of the

, which has a low density, and is spongy. It is narrow, with deep grooves supporting the

. Its anterior border, short and thick, articulates with the

. It has two small projecting alae (wings), which are received into corresponding depressions in the frontal bone to complete the foramen cecum. Its sides are smooth, and sometimes bulging due to the presence of a small

air sinus Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity. The maxillary sinuses are located under the eyes; the frontal sinuses are above the eyes; the ethmoidal sinuses are between the eyes and the spheno ...

in the interior. The

crista galli The crista galli (Latin: "crest of the rooster") is a wedge-shaped, vertical, midline upward continuation of the perpendicular plate of the ethmoid bone of the skull, projecting above the cribriform plate into the cranial cavity. It serves as an ...

projects upwards from the middle line of the cribriform plate. The long thin posterior border of the crista galli serves for the attachment of the

falx cerebri The falx cerebri (also known as the cerebral falx) is a large, crescent-shaped fold of dura mater that descends vertically into the longitudinal fissure to separate the cerebral hemispheres.Saladin K. "Anatomy & Physiology: The Unity of Form a ...

. On either side of the crista galli, the cribriform plate is narrow and deeply grooved. At the front part of the cribriform plate, on either side of the crista galli, is a small fissure that is occupied by a process of dura mater. Lateral to this fissure is a notch or foramen which transmits the

nasociliary nerve The nasociliary nerve is a branch of the ophthalmic nerve (CN V1) (which is in turn a branch of the trigeminal nerve (CN V)). It is intermediate in size between the other two branches of the ophthalmic nerve, the frontal nerve and lacrimal ner ...

; from this notch a groove extends backward to the anterior ethmoidal foramen.

Development

The cribriform plate is formed from the fetal age to the end of the first year, completing ossification. Deriving from the nasal capsule, formation begins specifically during the 5th week of gestation. Ossification begins at its most anterior part and proceeds in a posterior manner. The position also shifts from vertical during the 1st postnatal month to horizontal at the age of 6 months.

Keros classification

The Keros classification is a method of classifying the depth of the olfactory fossa. The depth of the olfactory fossa is determined by the height of the lateral lamella of the cribriform plate.

Keros Keros (; anciently, Keria or Kereia ()) is an uninhabited and unpopulated Greek island in the Cyclades about southeast of Naxos. Administratively it is part of the community of Koufonisia. It has an area of and its highest point is . It was ...

in 1962, classified the depth into three categories. * type 1: has a depth of 1–3 mm (26.3% of population) * type 2: has a depth of 4–7 mm (73.3% of population) * type 3: has a depth of 8–16 mm (0.5% of population) * type 4: has asymmetric depths (described by Stammberger)

Function

The cribriform plate is perforated by

, which allow for the passage of the

s to the roof of the

. This conveys information from smell receptors to the

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

. The foramina at the

part of the groove allow the passage of the nerves to the upper part of the

while the foramina at the lateral part transmit the nerves to the

Clinical significance

A fractured cribriform plate (anterior skull trauma) can result in leaking of

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless Extracellular fluid#Transcellular fluid, transcellular body fluid found within the meninges, meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricular system, ven ...

into the nose and loss of sense of smell. The tiny apertures of the plate transmitting the olfactory nerve become the route of ascent for a pathogen, ''

Naegleria fowleri ''Naegleria fowleri'', also known as the brain-eating amoeba, is a species of the genus ''Naegleria''. It belongs to the phylum Percolozoa and is classified as an amoeboflagellate Excavata, excavate, an organism capable of behaving as both an ...

''. This

amoeba An amoeba (; less commonly spelled ameba or amœba; : amoebas (less commonly, amebas) or amoebae (amebae) ), often called an amoeboid, is a type of Cell (biology), cell or unicellular organism with the ability to alter its shape, primarily by ...

tends to destroy the olfactory bulb and the adjacent inferior surface of the frontal lobe of the brain. This surface initially becomes the site of proliferation of the

trophozoite A trophozoite (G. ''trope'', nourishment + ''zoon'', animal) is the activated, feeding stage in the life cycle of certain protozoa such as malaria-causing ''Plasmodium falciparum'' and those of the ''Giardia'' group. The complementary form of the t ...

s of ''Naegleria fowleri'' and their subsequent spread to the rest of the brain and CSF. Because of its initial involvement and trophozoite presence in early phases of ''Naegleria fowleri'' infection, flushing of this region with saline using a device, to obtain ''Naegleria fowleri'' for diagnostic PCR and microscopic viewing, has been proposed for patients affected by

naegleriasis Naegleriasis, also known as primary amoebic meningoencephalitis (PAM), is an almost invariably fatal infection of the brain by the free-living protozoan '' Naegleria fowleri''. Symptoms include headache, fever, nausea, vomiting, a stiff neck, ...

, by (Baig AM., et al.) in a recent publication. Researchers have suggested the same route to administer drugs at an early phase of infection by using a "Transcribrial Device" that has been proposed to kill this pathogen at the place of its maximum proliferation. In 2017 the inventor of this device suggested that after slight modifications this method could be effective in delivery of stem cells to the brain as well. A recent Australian study has shown that the bacterium causing the tropical disease

melioidosis Melioidosis is an infectious disease caused by a gram-negative bacterium called ''Burkholderia pseudomallei''. Most people exposed to ''B. pseudomallei'' experience no symptoms, but complications can range from fever and skin changes to pneumon ...

, ''

Burkholderia pseudomallei ''Burkholderia pseudomallei'' (also known as ''Pseudomonas pseudomallei'') is a Gram-negative, bipolar, aerobic, motile rod-shaped bacterium. It is a soil-dwelling bacterium endemic in tropical and subtropical regions worldwide, particularly in ...

'', can also invade the brain via the olfactory nerve within 24 h by traversing the cribriform plate.

Etymology

The cribriform plate is named after its resemblance to a sieve (from Latin ''cribrum'', "sieve" + -form). It is also known as the horizontal lamina, and the lamina cribrosa.

Other animals

The cribriform plate is found in every

that has been studied. It serves the same function of allowing passage of the

Additional images

File:Cribriform plate and Olfactory nerve - animation.gif, Animation. Cribriform plate (green) and

s (yellow) File:Cribriform plate and Olfactory nerve - superior view.svg, Human skull, superior view. The calvaria is removed. File:Base of skull 3.jpg, Cribriform plate File:Ethmoid crista galli.jpg, Cribriform plate File:Sobo 1909 69.png,

Ethmoid bone The ethmoid bone (; from ) is an unpaired bone in the skull that separates the nasal cavity from the brain. It is located at the roof of the nose, between the two orbits. The cubical (cube-shaped) bone is lightweight due to a spongy constructi ...

(red) and

, seen from bottom.

Olfactory foramina The olfactory foramina, also known as the cribriform foramina (cribr- is "a sieve" in Greek), is the grouping of holes located on the cribriform plate. The cribriform plate forms the roof of the nasal cavity, and the olfactory foramina are in the ...

are illustrated. File:Crista galli and cribriform plate.webm, Video (1 min 32 s). Demonstrating

, cribriform plate, and

References

External links

* {{Authority control Bones of the head and neck Otorhinolaryngology de:Siebplatte