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the muscular system and reproduction system 

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the muscular system and reproduction system 

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The nervous system has two main parts: Central nervous system (CNS): Your brain and spinal cord make up your CNS. Your brain reads signals from your nerves to regulate how you think, move and feel. Peripheral nervous system (PNS): Your PNS is made up of a network of nerves.

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The human skeleton consists of 213 bones, of which 126 are part of the appendicular skeleton, 74 are part of the axial skeleton, and 6 are part of the auditory ossicles. Bone is a solid organ that appears pinkish white externally and deep red internally when in a fresh state.

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yes they do in fact,the adult worm possesses 95 diamond-shaped body wall muscle cells.

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Are there asexual worms?

A team of scientists has sequenced, for the first time, a tiny worm that belongs to a group of exclusively asexual species

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The earthworms each have two male openings and two sperm receptacles, which take in the sperm from another mate.

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Video ! HAPPY

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Secrets of the Worm Nervous System Revealed by New Color Palette | HHMI

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After color-coding all 302 neurons in the worm C. elegans, scientists have uncovered a vast “wireless” communication network.

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Well developed and concentrated nervous system.

Consists of 3 parts: the central, peripheral, and sympathetic nervous system.

Figure: Nervous System of Earthworm. Image Source: Meridian Technical Charter High School.

1. Central nervous system

It comprises of the anterior nerve ring or brain ring and the posterior ventral nerve cord.

Nerve ring

Comprises of cerebral ganglia or supra-pharyngeal ganglia, circumpharyngeal connectives, and subpharyngeal ganglia.

A pair of closely united white, pear-shaped, cerebral, or supra- pharyngeal ganglia, forming the so-called brain.

The brain lies dorsally in 3rd segment in the groove between the buccal cavity and pharynx.

From the brain a pair of thick stout circum or peri-pharyngeal connectives arise, one on each side, embracing the pharynx and meeting ventrally in4th segment by a pair of fused sub-pharyngeal ganglia.

In this way, a nerve collar is formed around the pharynx called a nerve ring or brain ring.

Ventral nerve cord

Originates from the sub-pharyngeal ganglia and runs backward in the mid-ventral line to the posterior end of the body.

It appears to be single but really is double and made of 2 longitudinal cords fused together in a transverse section.

In each segment from 5th to the last, it presents a slight enlargement or a ganglion.

Ganglia fused together as swellings representing the segmental ganglia.

Histologically, the nerve cord consists of nerve fibers and nerve cells.

Externally, nerve cords of Pheretima are solid an enclosed in a sheath called the perineurium.

Perineurium consists of 3 layers- the outer peritoneum, middle thin layer of longitudinal muscle fibers, and inner thick fibrous layer of an epineurium.

Both nerve cords are separated internally by a vertical epineurium.

In the region of segmental ganglia,2 cores of nerve fibers are completely fused along the middle line.

The ventrolateral region of the nerve cord contains bipolar and tripolar nerve cells all along the length.

Nerve cells occur more in ganglia.

Nerve cells and nerve fibers lie embedded in a mass of connective tissues, called neuroglia.

Dorsally, 4 giant nerve fibers (1 median, 1 submedian, and 2 lateral) runs through the mass of connective tissues along the entire nerve cord.

These nerve fibers surrounded by epineurium, all are tubular and filled with homogenous plasma-like matter which helps in their contraction.

These fibers are responsible for the rapid conduction of impulses throughout the nerve cord.

In the region of segmental ganglia, the partition between the 2 nerve cords are absent.

2. Peripheral nervous system

From the brain 8 to 10 pairs of nerves arises which supply to the prostomium, buccal cavity, and pharynx.

2 pairs of nerves arise from the circumpharyngeal connectives supply 1st segment and buccal cavity.

From the sub-pharyngeal ganglia, 3 pairs of the nerve arise supply to 2nd, 3rd, and 4th segments.

Each segmental ganglion of the ventral nerve cord gives off 3 pairs of lateral nerves.

One pair in front and 2 pairs behind the row of setae, they supply the various parts of the segment in which the ganglia are situated.

Thus, the nerve originating from the central nervous system to supply the different parts of the body constitute the peripheral nervous system.

Nerve are of mixed type, consists of both afferent or sensory fibers and efferent or motor fibers.

3. Sympathetic nervous system

It consists of an extensive nerve plexus situated in the wall of the alimentary canal and some other internal organs.

Such plexuses are connected with the per-pharyngeal connectives by fine nervules.

They help in coordinating the functions of the related organs.

Working mechanism of the Nervous System

All the activities of earthworm are under the control of the nervous system, though not necessarily of the brain.

Like higher animals, they have both sensory and motor neurons.

The nerves of the nerve cord have both sensory and motor fibers, i.e., mixed.

Sensory fibers start from a sensory cell or receptor organs in the epidermis and terminate in the ventral nerve cord in fine branches.

Near the branches in the cord, and forming a synapse with them, arise similar branches of motor fibers which run outward and terminate in muscles.

Stimuli or sensory impulses are conducted from the receptor by sensory fibers to the ventral nerve cord, from where they are reflected motor impulses along efferent fibers to muscles which contract.

The circuit of stimuli or impulses forms a simple reflex arc.

The movement of circular and longitudinal muscles are co-ordinated, so the contraction of one bring about relaxation of the other.

Giant fibers of the nerve cord conduct impulses more rapidly than other fibers resulting in sudden contraction of the whole body of earthworm when one point is strongly stimulated.

Video: Nervous System of Earthworm & its types By Studio Biology

References

Kotpal RL. 2017. Modern Text Book of Zoology- Invertebrates. 11th Edition. Rastogi Publications.

Jordan EL and Verma PS. 2018. Invertebrate Zoology. 14th Edition. S Chand Publishing.

About Author

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Nervous System of Earthworm is well developed and concentrated nervous system It consists of 3 parts: the central, peripheral, and sympathetic nervous system.

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Nervous system of Earthworm

Online Biology Notes

https://www.onlinebiologynotes.com › nervous-system-o...

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Earthworms produce both sperm and ova inside it and reproduce sexually .

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Is earthworms mitosis or meiosis .The combined result of meiosis 

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Is earthworms mitosis or meiosis .The combined result of meiosis 

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Reproductive System of Earthworm | Copulation

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The reproductive system of Earthworm includes male reproductive system, female reproductive organs along with copulation and reproductive cycle of earthworm at BYJU’S.

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The worm's nervous system is anatomically small, but at the molecular level its neuropeptide systems are highly complex, showing significant parallels to larger animals, and its synaptic connectome shows many features that are conserved in bigger brains.

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Scaling of the hydrostatic skeleton in the earthworm Lumbricus terrestris

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The structural and functional consequences of changes in size or scale have been well studied in animals with rigid skeletons, but relatively little is known about scale effects in animals with hydrostatic skeletons. We used glycol methacrylate histology and microscopy to examine the scaling of mechanically important morphological features of the earthworm Lumbricus terrestris over an ontogenetic size range from 0.03 to 12.89 g.

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Hydrostatic skeleton:

1. The hydrostatic skeleton of earthworms is divided into segments.

2. In all soft-bodied animals, the hydrostatic skeleton is a sort of skeletal structure.

3. A fluid-supported skeleton is known as a hydrostatic skeleton.

4. The hydrostatic skeleton of earthworms is segmented.

5. The coelomic fluid in each segment is largely isolated from the fluid in neighbouring segments by muscle septae, allowing segments to function as independent hydraulic units.

6. The circular fibres act to elongate and thin the worm radially, whilst the longitudinal fibres shorten it and produce radial expansion.

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They inhale and exhale via their skin

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Were U Wondering: Why do worms come out on the sidewalks after it rains?

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Things you Don't Know | Medicine for Stomach Worms: Why Deworming is Vital for Kids' Health

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mouth, pharynx, esophagus, crop, gizzard, and intestin

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At several points in the phylogeny, earthworms have transitioned from terrestrial to aquatic habitats and vice versa. Most species in Clitellata (the group that includes earthworms) are aquatic, so earthworm genomes may retain ancestral genes that enable transitions between habitats.

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Most worms have two bands of muscles: longitudinal muscles that run the length of the body and circular muscles that form circular bands around the body.

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The skin consists of the epidermis and a thin cuticle, which contains mucopolysaccharides acting as an antimicrobial barrier

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Hydrostatic skeletons

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Even so, hermaphrodites such as earthworms, flatworms, and hydra usually do not self fertilize. The combined result of meiosis (genetic segregation) followed by fertilization (genetic recombination) is greater variation among the offspring than possessed by the parents.

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In the asexual race, worms reproduce by fission without sexual organs.