What does it mean to Decussate?

1 : the action of crossing (as of nerve fibers) especially in the form of an X. 2 : a crossed tract of nerve fibers passing between centers on opposite sides of the nervous system. What is Isobilateral symmetry?
1. isobilateral – having identical parts on each side of an axis. bilateral, bilaterally symmetric, bilaterally symmetrical. symmetric, symmetrical – having similarity in size, shape, and relative position of corresponding parts.

What does Dorsiventrally mean?

1 : having distinct dorsal and ventral surfaces. 2 : dorsoventral sense 1. Why does decussation happen?
It is called the “somatic twist” hypothesis[i], and it asserts that neural crossings (technically called “decussations”) are the byproduct of a much larger evolutionary change—the switch from having a ventral (belly-side) nerve cord to dorsal (back-side) nerve cord. … Decussations are unique to vertebrates.

Why is decussation of pyramids important?

Decussation. The two pyramids contain the motor fibers that pass from the brain to the medulla oblongata and spinal cord. These are the corticobulbar and corticospinal fibers that make up the pyramidal tracts. … The pyramidal decussation marks the border between the spinal cord and the medulla oblongata. What is Isobilateral Tetrad?

Oct 08, 2018. Successive type: Each of the two nuclear divisions is followed by wall formation to form an isobilateral tetrad. Wall formation is centrifugal. This type is common in monocotyledons.

Frequently Asked Questions(FAQ)

Which plants have Isobilateral leaves?

Examples of the Isobilateral leaf are- monocots such as maize, lilies, irises, amaryllises etc. Note: Isobilateral leaves orient themselves as parallel to the main axis as well as parallel to the direction of sunlight.

What is the difference between Dorsiventral and Isobilateral leaf?

Anatomy of Flowering Plants, Anatomy of Dicotyledonous and Monocotyledonous… …

Dorsiventral Leaf Isobilateral Leaf
The number of stomata is more on the abaxial epidermis than the adaxial epidermis. Almost equal number of stomata is present on the abaxial and adaxial surfaces.
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What is an Isobront?

: a line on a chart marking the simultaneous development of a thunderstorm at different points on the earth’s surface.

What is Isohaline in social?

Isohaline is an ‘imaginary line’ on a map that connects all points of the ocean with same salinity. Explanation: Iso means ‘same’ and haline means ‘salinity’.

What is seafloor bathymetry?

What does it mean to be Dorsoventrally flattened?

Dorsoventrally flattened body means the body is flat from both surfaces, lower and upper surfaces. Example: This type of body is found in flatworms.

Which leaf is Dorsoventral leaf?

A dorsiventral (Lat. dorsum, the back, venter, the belly) organ is one that has two surfaces differing from each other in appearance and structure, as an ordinary leaf. This term has also been used as a synonym for dorsoventral organs, those that extend from a dorsal to a ventral surface.

What are Isobilateral leaves?

In the case of isobilateral leaf, the mesophyll tissue in the leaves is not differentiated. It is made up of either only spongy or palisade parenchyma cells. These type of leaves are similar in appearance on both the sides and hence, are called as isobilateral type of leaves.

What is Spinal decussation?

This crossover, or decussation, occurs just before the junction between the medulla oblongata and the spinal cord. This decussation of the pyramidal tract is the reason that brain injuries and strokes on one side of the head typically cause paralysis on the other side of the body.

What arouses the cerebrum?

Sensory axons, found in visual, auditory, and sensory impulses, activate RAS neurons in the brain stem. These neurons then relay information to the thalamus and cerebrum. Continuous stimulation of the RAS neurons causes the cerebrum to stay in an aroused state; this gives the feeling of alertness.

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Why do brain Fibres cross over?

Most sensory and motor pathways in the central nervous system cross the midline. Comparing between different neuronal pathways in different species suggest that, fibers crossing is most probably a response to the development of separated parts for the body during the process of evolution.

What is the functional consequence of Decussation of the pyramids?

The functional consequence of decussation of the pyramids is that each side of the cerebrum controls muscles on the opposite side of the body.

What is the level of decussation?

Decussation of the fibers (i.e., the crossing of fibers to the opposite side of the body) occurs at the level of the lower medulla, where 85 to 90% of the fibers cross to form the lateral corticospinal tract (LCST).

What does the medullary pyramid do?

The pyramids consist mainly of tubules that transport urine from the cortical, or outer, part of the kidney, where urine is produced, to the calyces, or cup-shaped cavities in which urine collects before it passes through the ureter to the bladder.

What is Decussate tetrad?

All pollen grains are arranged in one plane forming rhomboidal shape e.g., Annona muricata (Annonaceae). Decussate tetrad: Pair-wise the pollen grains are at right angle to each other, e.g., Magnolia grandiflora (Magnoliaceae). T-Shaped tetrad: … The first division of pollen mother cell is transverse to form a dyad.

What is the size of pollen grain?

A pollen grain represents a male gametophyte. They are generally spherical and measure about 25-50 micrometers in diameter.

What is the role of Sporopollenin?

The function of sporopollenin is to protect the pollen grains from external damages such as rain,high temp. Sporopollenin forms the outercovering of the exine & it is the most resistant organic material on the Earth ever known.

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Why Monocot leaves are called Isobilateral leaves?

Monocot leaves are called isobilateral leaves since both the sides of monocot leaves are more or less similar. Dicot and monocot leaves show considerable differences both in their morphological and anatomical characteristics.

What is the difference between transpiration and Guttation?

Transpiration is the process that occurs through the stomata and lenticels present in the leaves. Guttation is the process which takes place through hydathodes. In this process there is loss of Water as water vapour. Whereas here the loss of water happens as liquid water only.

What is Hypostomatic stomata?

Hypostomatic: A leaf is said to be hypostomatic when the stomata is present on the underside of the leaf. Epistomatic: A leaf is said to be epistomatous where stomata are present on the adaxial surface only. Such type of leaf is found in aquatic plants where the leaves float on the surface of water, e.g. Nymphaea.

What is adaxial epidermis?

The Adaxial Epidermis generally has a thick cuticle on the upper (adaxial) surface. … Stomata may occur on the upper epidermis but these are most frequent on the lower (abaxial) surface. The Abaxial Epidermis usually has a thin cuticle.

Do monocots have Piths?

Unlike dicot roots, a monocot root has a pith in the stele. It also contains vascular bundles that are composed of both xylem and phloem.

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