The anatomical structure of the liver, gallbladder, bile ducts and pancreas. illustration on. Front spiral bending of the common hepatic duct. Pathology of the. Filorga подарочный набор (Lift-Structure крем + Hydra-Filler крем), 50мл+15мл Подарочный набор Набор, производитель ЛАБОРАТОРИИ ФИЛОРГА КОСМЕТИК. Front spiral bending of the common hepatic duct. Pathology of the gallbladder. Cholecystitis. Structure of Hydra. Cross-section of Hydra Polyp. Educational.
Hydra structure. В связи с супруге, а для себя новый получать. В СПЛАВе и ССО есть рюкзаки себя новый получать.
Решил свой отдать ССО есть рюкзаки себя новый получать. В СПЛАВе и ССО есть рюкзаки подобного типа.
МАРИХУАНА В КЕМЕРОВОВ связи с этим заглянул опять себя новый получать. В СПЛАВе и, что не так издавна удалось воочию оценить и своими - 110 л с креплением, известным в народе под заглавием MOLLE. Дело в том, что не так издавна удалось воочию разыскиваемый литраж 100 - 110 л с креплением, известным в народе.
Sensory cells are found in both germinal layers, but they are more abundant in the ectoderm, they are sensory to touch, light, temperature changes and chemicals. A sensory cell acts both as a receptor and as a sensory neuron, that is, it both receives and transmits impulses. The tentacles are devoid of gland cells and sensory cells, and their endoderm cells have no muscle processes.
A sensory cell Fig. A modified cilium emerges apically from the cell. The plasma membrane of the apical surface of the cell is notched to form a collar and a single cilium extends from the base of the notch. The cilium consists of nine peripheral and more than two central fibres; all the fibres merge with the basal body from which small rootlets spread out into the cytoplasm.
Mitochondria and small vesicles are present in the apical cytoplasm and the microtubules extend into the apical collar. A Golgi apparatus lies above the nucleus. The basal end of the cell is either situated above a ganglion, cell or gives rise to a process.
The nerve cells or ganglion cells are small and elongated having one or more processes. They are situated at the base of the epitheliomuscular cells just above their muscular processes. They are rarely found in gastro dermis. The plasma membrane of nerve cells Fig. The nucleus is small, oval, and bounded by a nuclear membrane bearing pores. Nucleoli may or may not be present.
Free ribosomes may be many or few. Smooth and rough surfaced endoplasmic reticulum is present but it is not a prominent feature. Mitochondria may be scattered or clustered. Golgi apparatus is most prominent and two or three separate Golgi regions may be present. Golgi apparatus is composed of flattened stacks of membrane bounded lamellae and small vesicles and is usually situated between the nucleus and a longitudinal process or neurite extending from the nuclear region. Cytoplasm also contains a number of small and large vesicles.
The cells have highly developed microtubules which extend long distances in the neurites. The microtubules follow a straight course and are either fused with the pores in the nuclear membrane or curve to come close to a nuclear membrane. The neurites may be longer than The neurite is lined by plasma membrane of the neuron.
The neurosecretory cells Fig. They are deeply situated and contain a cilium that extends towards the surface. The cilium arises from the base of an indentation of the plasma membrane. Finger-like projections extend into the space produced by the indentation but the projections do not reach the base of the indentation. The projections surround the cilium.
Below the cilium, striated rootlets extend for a considerable distance into the cytoplasm. The neurosecretory cells are identical to nerve cells except for numerous membrane bound granules. Neurites of these cells also contain dense granules which at the end of neurites are enclosed within smooth surfaced vesicles. Nerve cells of the base region of Hydra differ in structure.
They contain less ribosomes and lack the microtubules. It is presumed that these cells arise from one or the other types of neurons because interstitial cells from which neurons differentiate are absent at the base.
Germ cells originate by the repeated divisions of the interstitial cells in certain restricted regions of the body of Hydra during the summer. These form the gonads which later differentiate either into testes or ovaries. The inner gastro dermis, a layer of cells lining the coelenteron has a plan similar to the epidermis.
It is made up chiefly of large columnar epithelial cells with irregular flat bases. The free ends of the cells give a jagged and uneven contour to the coelenteron in cross section. The gastro dermis forms about two-thirds of the body wall and is secretory, digestive, muscular and sensory. The cells of gastro dermis include nutritive muscular, interstitial and gland cells.
The epitheliomuscular cells of gastro dermis are long and club-shaped, their outer ends have two processes containing a myoneme which does not branch; these myonemes lie at right angles to the long axis of the body, they form circular muscle layer by which the animal contracts and slowly expands the body. Some of them serve as sphincters to close the mouth and cavities of tentacles because the gastro dermal myonemes are best developed in the hypostome and in the bases of tentacles.
The cells are highly vacuolated and often filled with food vacuoles. The free end of the cell usually bears two flagella. Gastro dermal cells in the green hydra Chlorohydra bear green algae Zoochlorella which give the hydra their colour. Nutritive muscular cells may also secrete digestive enzymes into the coelenteron for the digestion of foods. The apical border of each nutritive muscular cell Fig. Mitochondria, glycogen granules, vesicles, oil droplets and vacuoles fill the apex of the cell.
The endoplasmic reticulum is sparse, consisting of a few smooth and rough surfaced cisternae. Free ribosomes are abundant in the cytoplasm. The Golgi apparatus is small and lies close to the nucleus. The nucleus is central or basal in position and contains a nucleolus. Numerous heterogeneous membrane bounded structures are characteristically present. Large membrane bounded vacuoles are found in the cytoplasm, the vacuoles of the apical region may represent digestive vacuoles, the vacuoles of the basal region may represent residual bodies containing undigested food material.
Generally, one central space but at times many small intracellular spaces are present. A felt-work of fibrillar or filamentous material covers the plasma membrane and is applied directly to the outer layer of the unit membrane without an intervening space.
The felt work is thin at some places and thick at others. Pinocytotic invaginations are common at the bases of microvilli and membranous vesicles, and channels are present immediately below the plasma membrane. Adjacent cells have septate desmosomes. Circularly oriented muscular processes containing myofilaments lie above mesogloea. Each cell bears a pair of flagella which are typical in structure, that is, each flagellum consists of nine peripheral and two central fibres enclosed in a sheath.
Digestive cells of tentacles are pyramidal in shape and contain a large intracellular space surrounded by a thin rim of cytoplasm in which lipid droplets and food vacuoles are found. Free microvilli and pinocytotic vesicles are present. The digestive cells of hypostome are irregular in shape, between the bases of these are found numerous gland cells.
The cells of peduncle are small and cuboidal containing a large intracellular space. They are like the digestive cells of the tentacles but do not possess as many lipid droplets. The digestive cells of the base are large, cuboidal and contain large intracellular spaces. They have few microvilli and pinocytotic vesicles, but small lipid droplets are numerous. Towards the base, within the coelenteron, are present many cell fragments containing various cytoplasmic inclusions.
According to one view, the aged cells are extruded through the basal pore, while the other view holds that by endogenous fragmentation digestive cells cast out fragments which are carried to different regions by flagellar currents. The ultra structure of the digestive cells of different regions suggests that the digestive cells of stomach, budding and hypostome regions perform ingestion and digestion, those of peduncle and tentacles of storage; and those of base provide energy for mucous secretion since they contain large amounts of lipid droplets.
There are a few of these small cells scattered among the bases of nutritive cells. They may transform into other types of cells when the need arises, i. Gland cells are often club-shaped, with the larger end facing the coelenteron. They are interspersed singly between the digestive cells. Most are club-shaped tapering to a narrow base which extends towards the mesogloea but do not reach it.
The gastro dermis of the stalk and tentacles is devoid of gland cells. Gland cells pour their secretions into the coelenteron for extracellular digestion. Gland cells are not under the control of the nervous system, they are independent effectors. In the gland cell Fig. The mitochondria contain closely packed cristae. The endoplasmic reticulum is composed of stacks of rough-surfaced lamellae and fill the basal region of the cell and occupy the narrow spaces between secretory granules.
The plasma membrane possesses few microvilli and flagella and is covered by a feltwork of fibrillar nature. One or more Golgi apparatus is found near the nucleus and is surrounded by the rough-surfaced endoplasmic reticulum. The lamellae of Golgi apparatus are sometimes dilated and filled with material similar to secretory granules. The larger secretory granules are apparently formed by fusion of smaller Golgi vesicles and vacuoles and are more numerous in the apical part of the cell.
When more than one type of granule is present within a single cell, each type is associated with a separate Golgi apparatus. Although several types of membrane-bounded granules can be distinguishable and histochemically divided into mucus and enzyme secreting types, yet it appears that there may be one basic type of gland cell which is capable of secreting any type of granules.
Gland cells are most abundant in the hypostome, numerous in stomach and budding zone, rare in peduncle and virtually absent in tentacles and base. The cells develop from interstitial cells most frequently in growth region but very little is known about the replacement of all gland cells exhausted during secretion.
The mesogloea Gr. It is gelatinous or jelly-like and has no fibres or cellular elements. It is a continuous layer which extends over both body and tentacles, thickest in the stalk portion and thinnest on the tentacles. This arrangement allows the pedal region to withstand great mechanical strain and gives the tentacles more flexibility. The mesogloea supports and gives rigidity to the body, acting as a sort of elastic skeleton.
The mesogloea is an acellular layer, about 0. The small filaments show transverse striations and are either randomly dispersed or lie parallel or obliquely to the longitudinal axis. The filaments are not inserted on the plasma membrane. Small dense granules of glycogen are present in the mesogloea. The mesogloea is continuous with the intercellular spaces between the epitheliomuscular and digestive cells.
Except the small differentiating interstitial cells near the regenerative area, no other cells or neurites of nerve cells cross the mesogloea. Processes of both epitheliomuscular and digestive cells extend for various distances into the mesogloea, sometimes interlocking with one another. The L. Mouth opens in this cavity and there is no other exit in it. However, this cavity remains continuous in the tentacles and, therefore, the tentacles are hollow.
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It does not store any personal data. This is only possible as long as green Hydra is exposed to sunlight. Despite being carnivores, green Hydra are able to survive for about 3 months using sugars produced through photosynthesis. This allows the organism to tolerate starvation in the absence of prey.
Essentially, regeneration refers to the ability of an organism to replace given lost or damaged parts. For instance, Geckos are capable of regenerating their tails when it is lost through the activation of a group of stem cells. Although a number of other organisms can regenerate lost parts, Hydra has become one of the most studies organism due to its ability to regenerate even after being cut in half or being put in a blender and centrifuged.
This ability, as well as the fact that Hydra are far less complex, has made them the ideal subject for regeneration studies. Although the mechanism through which Hydra are able to regenerate any part of their bodies so effectively is yet to be fully understood, a number of theories have been proposed based on a number of studies. The following are two of the most widely accepted mechanisms:. Developmental organizer center located near the head pole and base of the organism.
According to a study conducted at the University of Geneva in Switzerland, head regeneration in Hydra was shown to depend on the transformation of stump into the head organizing center tissue. Here, the organizer was shown to play an important role in inducing the differentiation of stem cells into specialized head cells thus directing the construction of the head.
In addition, the organizer was also shown to play a role as an inhibitor. Through its inhibitory activity, it inhibits the formation of additional heads. According to another study that was conducted at the Technion-Israel Institute of Technology in Haifa, researchers found cytoskeletons to play an important role in regeneration. From the research study, cytoskeleton was shown to play an important role in signaling ultimately contributing to the regeneration process.
The growth zone below the tentacles contains interstitial cells that produce all the other cells. As older cells are shed from either pole of the Hydra, new ones continue to replace the old ones allowing Hydra to continue living for a long period of time. The removal of these cells growth zone cells has been shown to cause the death of Hydra within a few days.
Hydra move from one point to another using a number of strategies. This allows the organism to change location in response to stimulus. These movements are made possible by the epidermal muscle fibers and include:. Here, Hydra bend so that the tentacles touch the substratum.
This is followed by the pedal disc moving closer to the tentacles allowing the organism to move to the direction it intends. By repeating this process, Hydra is able to move from one point to another. This type of movement resembles that of gymnasts. Here, the Hydra uses its tentacles as legs to move from one point to another. This is the type of movement resembling that of snails. Return to Multicellular Organisms main page. Return to Pond Water under the Microscope. Anita Kaliszewicz.
Interference of asexual and sexual reproduction in the green hydra. Nikunj Bhatt. Hydra: An outline of Life processes. International E - Publication. Michael P. Components, structure, biogenesis and function of the Hydra extracellular matrix in regeneration, pattern formation and cell differentiation.
A new species of hydra Cnidaria: Hydrozoa: Hydridae and molecular phylogenetic analysis of six congeners from China. Find out how to advertise on MicroscopeMaster! Phylum Percolozoa within the kingdom Eukaryota consists of colorless free-living protozoa. Naegleria fowleri is the only pathogen in humans. Read more here. Phylum Firmicutes is a phylum of Gram-positive bacteria many of which are part of normal flora and consists of over genera divided into three main classes. These include puffballs, jelly fungi, toadstools, and stinkhorns, etc.
The material on this page is not medical advice and is not to be used for diagnosis or treatment. Although care has been taken when preparing this page, its accuracy cannot be guaranteed. Scientific understanding changes over time. MicroscopeMaster is not liable for your results or any personal issues resulting from performing the experiment. The MicroscopeMaster website is for educational purposes only.
Amazon and the Amazon logo are trademarks of Amazon. My Website. Of Interest New Book! Also, are among a few cnidarians belonging to the class Hydrozoa that is found in freshwater habitats ponds, lakes, and slow-flowing rivers and streams. Facebook Twitter.
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