WAEC and JAMB Biology 7 : Tissues and supporting system


Tissues and supporting system

In biology, tissue is a cellular organizational level that is midway between cells and a complete multicellular organism. A tissue is a collection of similar cells from the identical origin that perform a particular function. Organs in turn are obtained by a collection of several tissues.


The study of tissue is referred to as histology and when tissue is studied with respect to disease, it is known as histopathology. The standard tools for studying tissues are the paraffin block to which tissue is fixed and subsequently segmented, the histological stain, and the optical microscope.


In the past few decades, advancements in electron microscopy, immunofluorescence, and the utilization of frozen tissue sections have improved the feature that can be seen in tissues. With these tools, the standard looks of tissues can be studied in health and disease facilitates substantial enhancement of clinical diagnosis and prognosis.


Animal Tissue:

Animal tissues can be classified into four fundamental types: connective tissue, muscular tissue, nervous tissue, and epithelial tissue.


Several tissue types make up organs and body structures. Although all animals can by and large be well thought-out to have the four types of tissues, the appearance of these tissues can vary depending on the nature and form of the organism. For instance, the source of the cells containing a specific type of tissue may vary in terms of development for a variety of animal classification.


The epithelium in all animals is the derivative of the ectoderm and endoderm with a little input from the mesoderm, structuring the endothelium, a specific kind of epithelium that comprises the vasculature.


On the contrary, a true epithelial tissue is only available in one layer of cells knitted together through occluding junctions referred to as tight junctions, to form a selectively permeable wall. This tissue covers every surface of the organism that is exposed to the outside environment like you would obtain in the skin, the airways, and the digestive tract. Its sole function is for protection, secretion, and absorption. It is alienated from the rest of the tissues below by a lamina on the base.


Connective tissue

Connective tissues are composed of fibers. They are composed of cells divided by non-living substance referred to as an extracellular matrix. Connective tissue makes available shapes to organs and keeps them in place. The blood and bone are examples of connective tissue.


Just as you would deduce from the name, they support and connect other tissues. In contrast to the epithelial tissue, connective tissue characteristically has cells spread all through an extracellular matrix.


Muscular tissue

Muscle cells come together and form the energetic contractile tissue of the body referred to as muscle tissue or muscular tissue. Muscle tissue function is to generate force and cause movement, either locomotion or the movement of internal organs.


Muscle tissue is classified into three different categories: visceral or smooth muscle, which is created in the inner linings of organs; skeletal muscle, in which is found attached to bone making possible gross movement; and cardiac muscle which is seen in the heart, and which enables it to contract and pump blood all through the organism. The muscular tissue is the most elongated group of cells in the human body.


Nervous tissue

The nervous or neural tissue is made up of all cells that made up the central nervous system and peripheral nervous system. In the central nervous system, neural tissue come together to give rise to the brain and spinal cord while in the peripheral nervous system it forms the cranial nerves and spinal nerves in addition to the motor neurons.


Epithelial tissue

The epithelial tissues are made up of cells that envelop the organ surfaces like the surface of the skin, the airways, the reproductive tract, and the inner coating of the digestive tract.


The cells that made up the epithelial layer are connected through semi-permeable, tight junctions; and so, this tissue acts as a boundary between the outside environment and the organ it covers.


Apart from this protective function, epithelial tissue may as well be focused to perform secretion and absorptive function. Epithelial tissue shields organisms from microorganisms, injury, and water loss. The functions of the epithelia tissue is listed below:


• the epithelia cell of the body surface form the outer layer of skin.


• Within the body surface, epithelial cells forms lining of mouth and alimentary canal and guard these organs.


• epithelial tissues assist in the absorption of water and nutrients.


• epithelial tissues assist in the removal of waste product.


Types of epithelia tissue

The various types of epithelial tissues are listed below:


• Squamous epithelium,

• Cuboidal epithelium,

• Columnar epithelium,

• Glandular epithelium,

• Ciliated epithelium.


Skeletal Tissue

The skeletal tissue is of three types. The three types of skeleton or skeletal tissue are hydrostatic skeleton, endoskeleton and exoskeleton. Hydrostatic skeleton is seen in cold-blooded animals in addition to invertebrates. Human beings have endoskeleton. Exoskeleton is available in insects.


Hydrostatic Skeleton

It is seen in soft-bodied and cold-blooded animals. This skeleton has a coelom, which is a fluid-filled cavity. The coelom is covered up by muscles and the stiffness initiated by the fluid and the muscles provide the supporting construction for the organisms.


The fluid pressure in addition to the motion of the supporting muscles assists the organisms to modify shape and move. Invertebrates, the greater part of the earth’s living organisms are present in an enormous number of habitats. They could be seen in the deepest part of the oceans to the thickest forests.


These invertebrates possess a hydrostatic skeleton system that assists them to flourish in a different number of landscapes.


Echinoderms, cnidarians, annelids, nematodes and some other organisms use the hydrostatic skeleton for movement.


The Earthworm which is an annelid has no bone. Through hydrostatic skeleton it makes hole through the ground. Examples of echinoderms are the star fish and the sea urchin. The Jelly fish is a cnidarians.



The simplest explanation for endoskeleton is that it is the skeleton located in the body. It forms the frame work for the animal. The tissues and muscles are produced around the skeletal system and the well-developed forces are passed on to this skeleton.


The Endoskeleton supports the animal constitution. It is made up of mineralized tissues. In Phylum Chordata, Porifera and Echinodermata endoskeleton is present. Endoskeleton is created in the sub-class Coleoidae. The animals that belong to Phylum Chordata are all vertebrates in addition to human beings.


Phylum Porifera are sponge-like animals and is made up of about 5000 species. Its skeleton is a complex of organic fibres, a pedestal of calcite and aragonite and spicules of silica. Here the endoskeleton is for maintainance.


Phylum Echinodermata is made up of a variety of symmetrical marine animals such as the star fish, sea urchins and so on. It has an endoskeleton composed of calcium and is enclosed with spines.


Echinoderms have endoskeleton because they have an interior calcareous skeleton. But for motion, it makes use of the tentacles which are comparable to a hydrostatic skeleton.


The endoskeleton in chordates and echinoderms are formed from mesodermal tissue and it is taken to be the true endoskeleton. In Coleoidae, the exoskeleton has evolved into the inner structure. Example is cuttle fish.



Exoskeletons are skeletons that exist outside the body. It forms a shielding covering for the animals. It supports and also protects the animals. All crustaceans possess exoskeleton. Crabs, spiders, lobsters, insects are all crustaceans. Animals with exoskeleton are typically small.


This is due to the fact that big animals could not be sustained by exoskeleton and need bones to hold them up. Animals with exoskeleton possess a head and abdomen and in a number of cases, a thorax. The exoskeleton is supple and thin at the joints where it ought to bend. The outsized exoskeletons are referred to as shells. Tortoise is an animal that has a shell and endoskeleton.


The simplest type of skeleton is the hydrostatic skeleton obtained in a lot of cold-blooded organisms and soft-bodied animals. The pressure of the fluid and action of the adjoining muscles are used to alter an organism’s figure and generate movement. This fluid filled cavity is referred to as the coelom.


The human Skeletal System

The supporting tissues of animals which frequently serve as a protection for the body or parts of it and play a crucial role in the animal’s physiology is known as skeleton.


Skeletons can be divided into two major types in relation to the comparative location of the skeletal tissues. When these tissues are situated outside the soft parts, the animal is said to possess an exoskeleton. If they take place deep inside the body, they constitute an endoskeleton.


All vertebrate animals have an endoskeleton, but the majority as well has components that are exoskeletal in origin. Invertebrate skeletons, nonetheless, demonstrate far more disparity in position, morphology, and materials used to assemble them.


The vertebrate endoskeleton is typically made up of bone and cartilage; with the exception of a few fishes that possesses skeletons that do not have bone. In addition to an endoskeleton, a lot of species have distinct exoskeletal structures composed of bone or horny materials. This dermal skeleton makes available support and safeguard at the body surface.


A lot of structural components constitute the human skeleton, which includes the collagen, three diverse types of cartilage (hyaline, fibrocartilage, and elastic, as well as a lot of bone types-woven, lamellar, trabecular, and plexiform.


The vertebrate skeleton is made up of the axial skeleton –the skull, vertebral column, and related structures and the appendicular skeleton which consists of limbs or appendages. The essential plan for vertebrates is comparable, though great variations take place in relation to functional demands placed on the skeleton.


Axial skeleton

The axial skeleton provides support for the organs of the head, neck, and torso and as well offers them protection. In humans, the axial skeleton is made up of the skull, ear ossicles, hyoid bone, vertebral column, and rib cage.



The adult human skull is made up of eight bones which make up the cranium, or brain box, and 13 facial bones that sustain the eyes, nose, and jaws.


There are as well three small, paired ear ossicles—the malleus, incus, and stapes—inside a hollow in the temporal bone. The totality of 27 bones represents a huge drop in skull elements all through the course of vertebrate advancement. The three components of the skull are the neurocranium, dermatocranium, and visceral cranium.


The brain and certain sense organs are sheltered by the neurocranium. Every vertebrate neurocrania grow in the same way, beginning as ethmoid and basal cartilages beneath the brain, and as capsules partially encircling the tissues that finally form the olfactory, otic, and optic sense organs. Additional growth manufactures cartilaginous barricades around the brain.


Vertebral column

The vertebral column is an endoskeletal segmented shaft of mesodermal derivation. It protects the spinal cord, acts as sites for muscle attachment, offers flexibility, and support, especially in land-based tetrapods where it has to maintain the weight of the body.


Hard, spool-shaped bony vertebrae exchange with tough but flexible intervertebral discs. Every typical vertebral body (centrum) has a bony neural arch extending dorsally. The spinal cord pass through these arches, and spinal nerves come out through the spaces.