Anatomy And Morphology Of Animal Tissues

May 09, 2023, 16:45 IST

Animal tissues are collections of identical cells that have been specially trained to carry out a single function. Often these tissues are made of one or more types of specialized cells that are held together by an extracellular matrix. Here, let’s learn more about these tissue cells and their morphology in detail.

Types of Animal Tissues

During development, every individual cell differentiates to perform specific functions. These individual cells which perform similar functions are grouped together and termed as tissues. Animal tissue can be broadly classified into two:

1. Simple Tissue - A collection of cells that share a common origin, form, and structure and cooperate to carry out a particular function.
2. Compound Tissue - A set of cells with varying structures and functions that work together to fulfill a single function.

Furthermore, based on morphology/anatomy, function, and location, they are classified into 4 types:

1. Epithelial Tissue
2. Connective Tissue
3. Muscle Tissue
4. Nervous Tissue

Epithelial Tissue

Epithelial tissues are simple tissues that typically include a sheet of cells that covers internal organs and external body surfaces. Thus they can protect, absorb, transport as well as excrete. They are typical base membranes that often act as barriers between nearby, and underlying tissues. Also, they usually lack blood vessels. These tissues exist in various shapes.

• Squamous Epithelium

It is composed of flat sheet-like cells with noticeable nuclei and irregular borders. They usually connect neighboring cells and are often referred to as the pavement membrane. For example, the squamous epithelial lining in the buccal cavity, the alveoli of the lungs and the tongue as well as skin.

It shields the body against mechanical harm, dehydration, and microbial invasion.

• Stratified Epithelium

Stratified epithelium has a layered appearance and hence the name. This epithelium's primary job is to protect the underlying tissues from mechanical and chemical stress. They also cover the throat, buccal cavity, and skin's dry and moist surfaces.

• Cuboidal Epithelium

This structure is composed of a single layer of cubical cells with a round nucleus. Cuboidal epithelium can be found in the exocrine pancreas, salivary glands, sweat glands, and thyroid vesicles. It can also be found as microvilli, which expand the absorptive surface area, in the intestine and the tubular portion of the nephron.

Their primary role is absorption and secretion.

• Columnar Epithelium

It is made up of a single layer of pillar-like, long, thin cells with nuclei at their base.Free surface may have microvilli. It creates the mucous membrane and is found lining the small intestine, colon, oviducts, gall bladder, and bile duct.

They also primarily aid in absorption and secretion.

Connective Tissue

It is one of the most common tissues that offers a structural framework and supports various other tissues that makeup organs.The primary role of connective tissues is to prevent the displacement of organs from bodily movements. The anatomical components of these tissues include an intracellular substance called matrix, connective fibers, and tissue cells. The various connective tissues in our body are:

• Adipose Tissue

Often large cells that store lipids combine to form the loose connective tissue known as adipose tissue. Most frequently, these cells build up in vast numbers to store fat.

• Blood

These are specialized fluid tissues that are made of WBC, RBC, and platelets. These connective tissues are suspended in a fluid called plasma. These blood tissues aid in carrying different substances throughout the body of an animal.

• Bones, Ligaments, and Cartilage

Osteocytes or bone cells are heavily saturated with calcium phosphate. Thus they are strong and ideally aid in protection and support. Whereas ligaments are highly elastic in nature. They often connect two bones. These ligaments strengthen the joints and aid in normal movements.

Cartilages are flexible, semi-rigid yet soft structures made of chondrocytes. In humans, they are found in the outer ears, nose tips, larynx, and trachea. They also make up the entire skeleton of animals like sharks and rays.

Muscle Tissue

Muscle cells are mainly involved in body movement. They are made up of myofibrils. These myofibrils are cell organelles of the muscle. Furthermore, each muscle is composed of several long, cylindrical fibers that are organized in a parallel fashion. Based on morphology and function, these tissue cells can be classified as follows.

• Skeletal or Striated Muscles

These are voluntary muscles that are connected to the bones and control the movement of the body.

Skeletal muscles are often striated or striped and hence they are also known as striated muscles. The striated appearance of the muscle fibers is caused by their cylindrical, unbranched, elongated cells with alternating light and dark bands. They are multinucleate. They are seen in the triceps and biceps of the arms when they undergo contraction.

• Smooth or Non-Striated Muscles

These muscles are spindle-shaped with broad mid-section and tapering ends. They are uninucleate. Also, none of their fibrils bear any striations and thus they look smooth without any striations. Most importantly, smooth muscles are involuntary in nature. This kind of smooth muscle is found in the walls of internal organs such as the stomach, blood arteries, urinary bladder, and intestinal villi.

• Cardiac Muscles

The heart is made up of unique contractile muscle tissue known as cardiac muscles. These muscles are composed of cylindrical, branching, and uninucleate muscular fibers. Between the heart's myocardial cells are special structural formations called intercalated discs. They are crucial in transmitting signals between cells and joining cardiac muscle cells together.These are involuntary muscles that contract and dilate rhythmically.

Nervous Tissue

Nervous tissues are made of distinct cells called neurons. These neurons are the functional and structural components of the whole nervous system. The main function of neurons is to transmit impulses. Each neuron has a cyton or cell body, axon and dendrite. They also have long and slender processes called nerve fibers which help in transmitting signals. They have the capacity to receive stimuli from the body or the environment and send signals to various body regions.

Frequently Asked Questions (FAQs)

Q1. What is animal tissue?

Ans. Animal tissues are defined as a collection of cells that have a common function. On the whole, each tissue might vary in its origin, function, and structure.

Q2. What are the 4 types of animal tissue?

Ans. The four major types of animal tissues based on function and morphology/anatomy are - Epithelial tissues, nervous tissues, muscular tissues, and connective tissues.

Q3. Which is the most abundant animal tissue?

Ans. The most abundant tissue in the body of an animal is connective tissue. It is the vital tissue that separates, supports, binds, and connects to every other tissue and organ in the body.

Q4. Which is the most abundant muscular tissue in humans?

Ans. The most abundant type of muscular tissue in humans is the striated or skeletal muscle tissue.

Q5. What is the main difference between animal tissue and plant tissue?

Ans. The main distinction between plant and animal tissue is that the former has cellulose-based cell walls, while the latter has a protein-based membrane.