Skeletal And Organs Systems In Animals

Definition: Skeletal system is the system consists of bones and other connective tissues which protect and support the body.

Animals are divided into 2 catogories:

1. Vertebrates
2. Invertebrates
3. Vertebrates: Those animals which have a backbone and a skeleton.

Examples:

1. 1-Birds
2. 2-Amphibions
3. 3-Reptiles
4. 4-Fishes
5. 5-Mammals

Invertebrates: Those animals which have no backbone. Invertebrates may include:

Examples

1. Phylum porifera (sponges)
2. Phylum cnidaria (jelly fish, coral)
3. Phylum nematoda ( clam worm, Tube warm)
4. Phylum Annelida ( Earth worms, Leeches)
5. Phylum Echinodermata ( starfish)
6. Phylum Arthopoda( insects)
7. Phylum molluscs ( octopus)

Skeletal system in invertebrates: Many invertebrates use their body fluids for internal support.

Types of skeleton:

1. Hydrostatic skeletons
2. Exoskeletons
3. Endoskeletons

Hydrostatic skeletons: some animals have a form of some internal support called hydrostatic skeleton. such as in:

1. sea anemones
2. slugs
3. jellyfish
4. octopuses
5. earthworm

The hydrostatic animal is a core of liquid surrounded by a tension-resistant sheath of longitudinal and circular muscles. The invertebrate hydrostatic skeleton can take many forms and shapes such as gastrovascular cavity of acoelomates, a rhynchocoel in nemertines, a coelom in annelids or a hermocoel in mullusca. Overall the hydrostatic skeleton of invertebrates is an excellent example od adaptation of major body functions.

Hydrostatic skeleton in sea anemones:Hydrostatis skaleton in sea anemones allows them to shorten or close, when longitudinal muscles contract, or to lenghten or open when circular muscles contract

Exoskeleton

1. 1-In Arthopod ( such as lobsters):- In arthopod the epidermis of the body wall secrets a thick, hard cuticle( made of the polysacharides chitin) that water proofs the body. The cuticle also protects and supports the animal,s soft internal organs. In crustaceans ( crabs, lobster, shrimp), the exoskeleton contains calcium carbonate crystals that make it hard and inflexible, except at the joints. Certain regions of the arthopod body have a thin, flexible cuticle, and joints. It is in these areas that pair of antagonistic muscles function through a system of levers to produce coordinating movementEndoskeleton

1. In Phylum porifera( sponges): The endoskeleton of sponges consists of mineral spicules and fibers of spongin that keep the body from collapsing. Because adult spnges attach to the substrate, they have no need for muscles attavh to the endoskeleton.
2. In echinoderms: Similarly the endoskeleton of echinoderms ( sea stars, sea urchins) consists of small calcareous plate called ossicles. Thus in these animals the endoskeleton is used for protection and support not locomotion.

Phylum platyhelminths ( flatworms): Zoologists identified neurosecretory cells in various flatworms more then 30 years ago. These cells are in the cerebral ganglion and along major nerve cords. The neuropeptids that the cells produce functions in regeneration, Asexual reproduction and gonad maturations. Example: Neurosecratory cells in the scolex of some tapeworms control sheddings of the proglottids or the nitiations strobilization.

Phylum nematodea (Ascaridida): Although no classical andocrine glands have been identified in nematodes, they do have neurosecratory cells associated with the central nervous system. The neuropeptde that this nervous tisssues produce apparently controls ecdysis of the old cuticle. They neuropeptide is released after a new cuticle is produced and stimulates the excretory gland to secret an enzyme in to the space between old and new cuticle.

Phylum Echinoderms: The endocrine system of echniderms provide few insights into the evolution of chordate endocrine systems, because echinoderm hormones and endocrine glands are very different from those of chordates.

Example: The radial nerves of sea stars contain a neuropeptide is injected into a mature sea star, it induces immediate shedding of the gametes, spawning behaviour, and meiosis in the oocytes. The neuropeptide also causes the release of a hormone called maturation-inducing substance. which has various effects on reproductive system.

1. They do not have neurosecratory cells
2. They have neurosecratory cells
3. They do not have neurons
4. They have neurom cells
5. Neuropeptide are not released and no ecdysis
6. Neuropeptide are released to control ecdysis
7. Such as sponges

Comparison between phylum molluscs and phylum annelids

1. They have no Juveline hormone
2. They have no gonadotropin hormone
3. Have no osmoregulatory hormone
4. Ring of ganglia
5. The neuropeptide that these cells produce help regulate heart rate, kidney function and enerygy metabolism
6. Such as octopus