Free Biology NEET Video Lectures for Structural Organisation In Animals

00:00:33 [Music] [Applause] Welcome to session one chapter 7 structural organization in animals from class 11th myself Jalaja Sajjiv PGT bio from KV Keshopuram. First of all the introductory session. You know the basic unit of life it is cell again the functional unit of life it is also right cell. What is the bodybuilding unit of an organism? Yes, your answer is correct. Cell. How will you define a cell based on the above of questions? It is the building unit. So it is the structural and functional unit of an

00:02:00 organism. The basic structural and functional unit of an organism that is called as a cell. Now what is a tissue? A group of cells having similar origin which will contribute a common function that we can call it as a tissue. Now when a group of tissues doing a common function we can call it as an organ. when a group of organs together contributes to a common function. We can apply the term organ system. Thus in short an organism is an assemblage of different organ systems meant for doing different functions.

00:03:28 Now come to the different aspects of this chapter structural organization in animals. What are the different types of tissues based on structure and function? How can you classify? How can you group or how can you categorize the tissues based on its structure as well as function? See here you can see so many different diagrams of tissues. First here you can see the epithelial tissues, different types of epithelial tissues, then muscular tissues. here different types of muscular tissues. Now see the different types of

00:04:24 connective tissues and here you can see the nervous tissue neurons. So in short we can categorize the different the tissues into four different groups. Yes. epithelial tissue, muscular tissue, connective tissue and nervous tissue. So these are the four different types of tissues present in animals based on structure as well as function. Now first category the epithelial tissue it covers the outer surface of an organ. Moreover, it will form a lining layer on the cavities of all the hollow organs.

00:05:37 Now what are the general characters or salient features of this epithelial tissue? The cells of these epithelial tissues they may be arranged in one or many rows, many layers. And these cells are normally arranged compactly without any intercellular spaces and the lowermost layer of the cells. They are lying on a basement membrane. They undergo cell division and regeneration throughout their life. The free surface of these cells, these epithelial cells may be either smooth, you can see here the diagram, the free surface, it

00:06:47 may be smooth or it have celia or microvilli. Here in this one you can see the micro will on the free surface of this epithelial tissue. So it may have either free surface or it may have a celia on its free surface or microvilli on its free surface. There are three different types of cell junctions occur between the epithelial cells. Now what are these different types of cell junctions that we can observe within these epithelial cells. There are three different types. The first one that is tight

00:07:46 junctions. Second one is known as adhering junctions. The third one that is known as gap junctions. First one tight junctions. You know if the cells are arranged very compactly very tightly it will stop the leakage of molecules across the tissues. So these tight junctions they help to stop leakage of molecules across a tissue. The second category that is adhering junctions. It will cement the neighboring cells together. The third one gap junctions. It will permit communication between the neighboring cells through the

00:08:55 cytoplasmic connections existing between the cells. So in short there are three different types of cell junctions that we can observe within an epithelial tissue. tight junctions, adhering junctions and gap junctions. Now what are the general functions of these epithelial tissue? What they contribute? They cover and they protect all the underlying tissues from mechanical injuries. It helps in secretion. Similarly, it helps in absorption of molecules. It contributes even in excretion. It helps in sensation.

00:10:13 Now, types of epithelial tissues. What are the different types of epithelial tissues? First, we can include these epithelial tissue into two major groups. The one is covering epithelial tissue. It will cover and protect the different body parts organs. The second category that is glandular epithelial tissue which can act as a gland. Now based on the number of layers of cells we can classify these epithelial tissues into two different groups. symbol epithelium and other is compound epithelium. First category is symbol

00:11:15 epithelium. You see here the diagrams you can see all these are examples of symbol epithelium. Why it is called as a symbol epithelium? Because it has only one layer of cells. It is thinwalled. Since it has only one layer of cells, it is thinwalled and seen in areas with minimum wear and tear. Why these type of tissues are seen in areas with minimum wear and tear? Again the answer is correct here. It has only one layer of cells. Moreover, it is thin wall also. So it is seen in areas with minimum wear and tear. Now what are the

00:12:13 different types of symbol epithelial tissues? You can see scammos epithelial tissue then columnar epithelial tissues even celiated epithelial tissues and cuboidal epithelial tissues. Squamos, cuboidal, columnar and celiated epithelial tissues. First category squamos epithelial tissue. Here you can see the diagram of a squamosep epithelial tissue. You see these are thin and flat and single layered cells. They are thin cells flat. Now regarding its shape, it is polygonal in shape. Cells have irregular

00:13:25 boundaries. Most of the time its boundary is irregular. So they have a irregular boundaries like this and see how many nucleus in this tissues. Uh normally it has only one nucleus at the center. That means again it is uni nucleiated. And regarding its position of the nucleus, you can see the nucleus exactly at the center. So they are thin and flat and polygonal cells. Cells have irregular boundaries. They are uni-ucleated and nucleus is seen exactly at the center. Now in our body where it can be

00:14:28 seen they are seen in the alvolus of lungs. Similarly in the bowman's capsule of nephrons the unit of kidney inside the blood vessels it is seen as a lining. It helps in exchange of gases and similarly filtration. So these are the different types of epithelial tissues as already I have told you. Now coming to the second type that is cuboidal epithelium. You see here made up of cube like cells. Cells are cubike. You can see here. And how many layers? Only one layer. Uni-layered. Again nucleus when you are

00:15:45 observing you can see the nucleus at the center of the cell. Now in our body in which part it can be observed. It is seen in the duct as well as in the tubular part of the nephrons. Since they are present in the ducts it helps in secretion and in the tubular part. PCT, DCT, Henley's loop and all it helps even in absorption also. Now the third one that is celiated epithelium. Again you see here the diagram and uh try to identify the characters. Regarding the number of layers of cells, both are seliated

00:16:49 epithelium. Regarding the number of layers of cells, it has only one layer of cell. Now, regarding the shape, it may be cuboidal or it may be columnar tall and pillar like cells. Now, why they are called a celiated? because they have celia on its free surface where these tissues are seen in our body. Yes, they are seen in the bronchioles and similarly they are seen in the fallopian tubes. Fallopian tube means ovid duct. Now what are their functions or what is their significance? They helps in the movement of

00:17:42 mucus in only one direction and they helps in the filtration of air. In the case of ov duct or fallopian tube they help in the movement of. Now coming to columnar epithelium. Here you can see the columnar epithelium. They are tall long and pillar-like cells. See how many layers of a cells only one layer of a cells that is arranged on the basement membrane. So they are uni-layered, they are tall, they are pillar like and they are the cylinder cells. Now regarding the position of a nucleus, see these two diagrams. You can

00:18:46 see the difference here. The nuclei are seen at the base of the cells and they have micro villi on its surface on its free surface. Some of these columnar epithelium they have microilli where they are seen in our body. They are seen in the lining layer of stomach and intestine. Now since they are seen in the lining layer of a stomach and intestine they help in secretion and absorption. Now you can see the second category of epithelium that is compound epithelium. First category was simple epithelium

00:19:46 with only one layer of cells lying on the basement membrane. Here the second category that is compound epithelium. See the diagram here compound epithelium means many layers of cells. You can see many layers of cells lying on the basement membrane. So it is multi-layered epithelium. Since it is multi-layered, they are commonly seen in areas with rapid wear and tear. And here the lowermost layer of the this epithelial tissue the lowermost layer of cells they are lying on the basement membrane. You can see here in this

00:20:46 diagram and they covers the dry surface of our skin. It is seen in the buckle cavity as well as ferings. It is seen as a lining layer in the salivary duct as well as in the pancreatic duct. In the glands of salivary glands in the salivary duct similarly in the duct of the pancreas it can be seen as a lining layer. They helps in the function protection. Similarly, they helps in absorption and they helps in secretion. Now coming to the types of compound epithelium. Stratified epithelium. The first

00:21:56 category it is made up of five to eight layers of cells. Here you can see the diagram of a stratified epithelium. Many layers are present here. Five to eight layers of cells are present in the stratified epithelium. Strata means layers different layers are present and different layers of these cells when you are observing you can see that they are also of different types. Different types of cells. You can see here they divide and add new and new cells to the topmost parts. They are seen in the epidermis of

00:22:52 the skin and ureitra and in the larynx. The second category that is known as transitional epithelium. Here again you can see the diagram of a transitional epithelium. Many layers are present multi-layered. The basal layer that is seen in or the lower layer of a cell seen just above the basement membrane. They are more stretchable. This is the most important point coming here. They are more stretchable. As I have already told you, they are multi-layered and at the same time they are thin. Basin layer when you are observing

00:23:55 they are normally cuboidal in shape. They are seen in the uterus. They are seen in the uritus. Not in the uterus. They are seen in the urittors. They are seen in the urinary bladder and renal pelvis. Now the next type that is glandular epithelium. They are either cuboidal or they may be columnar epithelial cells. Here it is written glandular epithelium. It means they can act as a gland. Now depending upon the number of cells present in the gland, we can divide it into two types. One is unisellular glands and the other

00:25:03 is multisellular gland. The first category that is unisellular glands. The term itself indicates these glands they contains only a single cell. So here you can see the diagram of a unicellular gland. It has only one cell. So that single cellled gland that is known as unicellular gland. Where they are commonly seen? They are commonly seen in the mucosa of stomach and in the intestine. They are seen in the trachea and nasal chambers. They are commonly called as go blood cells. Very important aspect again. What

00:26:03 are goble blood cells? The single cellled glands they are known as goble blood cells. Mainly they are seen in the elementary canal. So what are goble blood cells and where they are located? single cellular unisellular glands they are known as goble blood cells and they are seen in the elementary canal. Now coming to the second category of glands they are the multisellular glands and these multisellular glands again of different types. First one simple gland have a single and unbranched duct to carry their

00:26:58 secretion. Since it is a single duct and it is an unbranched duct. This type of glands that is known as a symbol gland. example sweat gland present in the skin and sebaceous gland again present in the skin. So these two are typical examples of simple gland with a single and unbranched tubular duct. Now coming to the second category they are known as compound glands. It has branched ducts to carry their secretion. For example, mammary glands, milk secretreting gland and the bruner's gland. Now, where

00:27:52 these Bruner's glands are seen in the body? They are seen in the small intestine. Now coming to the category of glands based on the presence of ducts. If it posess a duct or is it have a duct or no no ducts. So based on the presence or absence of ducts we can classify again glands into different types. The first category it is known as exocrine gland. They have to carry they have a ducks to carry their secretions to the site of action. So it is known as exocrine glands. Glands with well-developed ducts

00:28:51 to carry their secretion. So they are known as ducted glands. Since it have a duct, they are called as ducted glands. For example, salivary gland, mammary gland and sweat glands. All these have well-developed ducts to carry their secretions. So it is known as ducted gland or exocrine glands. Now the second category that is endocrine glands they are ductal glands. It means they don't have any ducts to carry their secretion to the target site. So ductilus glands are known as endocrine glands.

00:29:54 their secretion are known as hormones. The secretions of ductilus glands are collectively known as hormones. And you know all the hormones are proteinatious molecules. They are secreted to the blood since they don't have any duct. how they are transported to different parts of the body to the target sides. So it is carried by the bloodstream to the different site of action. For example, the uh thyroid, pituitary gland, adrenal gland, thymus gland. All these are examples of endocrine glands or ductilus glands.

00:30:52 Now there is that another interesting term coming here heterocrine glands commonly they are known as mixed glands. Mixed in the sense it has some portion is having duct some portion is without ducts. That means some portion is acting as exocrine part exocrine gland and some part act as endocrine gland. Since it is a mixed gland we can call it as composite gland. So which gland is known as composite glands? Mixed glands or even heterocrine glands. They have both exocrain part and endocrine part. They

00:31:46 are partially ductus and at the same time partially ducted ones. Typical example is pancreas. Now coming to some of these NCRT questions. Where do you find celiated epithelium in the animal body? You have listened to the session. Now you can answer and what are their characters? So unilayered and here where do you find the seliated epithelium in the animal body? It is present in the bronchioles as well as in the ovduct or fallopian tube. Now coming to the next aspect distinguish between a symbol and

00:32:57 compound epithelium. You know simple epithelium it is made up of only one layer of thin walled cells and they are seen in areas with minimum wear and tear. Compound epithelium they are multi-layered epithelium made up of many layers of cells. They are seen in areas with rapid wear and tear. And the lowermost layer of cells they lie on the basement membrane. Distinguish between symbol and compound gland. Symbol gland they have a single and unbranched duct. Already I have given you the example. Sweater gland.

00:34:00 and sebaceous gland. Compound gland has branched ducts. For example, mammary gland. Bruner's gland. Bruner's gland is seen in the small intestine. Now coming to nervous tissue. Ectodermal in origin. You know there are three different germ layers ectodorm, misodm and endodm. So this tissue nervous tissue it is ectoermal in origin. It is meant for control, coordination and responses to stimuli. Now what are the important properties of this nervous tissue? The special properties of nervous tissue it

00:35:01 is excitability and conductivity. They lack intercellular matrix. Similarly, they lack the power of cell division. So these are some of the special properties of nervous tissue. incitability, conductivity and they lack intercellular matrix and they lack the power of cell division. Here you can see the structure of a neuron. What is a neuron? It is the unit of a nervous tissue. So it is known as nervous cell. So nervous cell is otherwise known as neuron and you can see the diagram of the neuron here with the different

00:36:02 parts. Now regarding the composition of a nervous tissue it is not only made up of nervous cells. It contains nervous cells then neurogle cells, ependimal cell and neuroscratory cells. Now the structure of a typical neuron nervous cell is known as neuron. The unit of nervous tissue, it is the structural and functional unit of nervous system. And regarding the parts of a neuron or a nervous cell, the first part, this part you can see here in the diagram and this we will call it as sitone. It is also known as cell

00:37:02 body and it has a granular cytoplasm inside and this granular cytoplasm of the neuron that is known as neuroplasm it contains small number of mitochondri Then you can see a large nucleus at the center. A single large nucleus you can see at the center of the cyclone. Then numerous fine threadlike structures you can see in the sone and those fine and threadlike structures which help it to conduct nerve impulses and present in the cyclone that is known as new fibbrals. Now there is yet another structure the granular

00:38:01 spherical basopilic structures small structures granular structures they are known as nissil granules. Niss's granules are also seen in the sitone. Now coming to the nerve process dendrons the small branches arising from the cyone. From the cyone or cell body there arise aes small branches and those small branches we will call it as dendrons. Then when the dendrons branches those branches of dendrons are known as dendrites. Here again you can see the diagram and in this diagram these are the

00:38:55 dendrons. So these small branches arising from the cyclone they are known as the dendrons. Branches of dendrons are known as dendrites. So all these are the dendrites. they will carry the stimuli the messages into the cyclone from different parts of the body into the cyclone. Now here you can see a long branch and this long branch that arise from the cyone is known as axone. The branch of axone is known as axonite. Since here the branch of dendron is known as dendrite. The branch of axon is known as

00:39:43 axonite. And this whole axon in some of the neurons it is covered by a sheath fatty sheath. It is known as myeline sheath. And this myeline sheath it is made up of a cells called as shwan cells. Now you can see at the end of this uh axon small spherical structure globular structure no like structure synaptic vesicles. So all these are the nerve processes dendrons the small branches arising from the sitone and already I have told you it will carry messages from different parts to the cyclone branches of a dendron is

00:40:43 dendrid axone the long branch arising from the sone it carries impulses away from the cytoone it's covering covering of the axone is known as milein sheath. Now the cytoplasm seen inside the axone is known as exoplasm. Already I have told you shan cells it forms the milein sheets. Now synaptic knob the small noble like structure seen at the end of the axon. Now what is meant by a syninnapse the junction between two neurons? It there is a a little small gap. So that gap between the two neurons that

00:41:50 is called as synaptic clft the axonite of one neuron links with the dendrite of the neighboring neuron and this junction between the two neurons that is known as synapse and there is a minute gap between these two that is known as synaptic clft. Now coming to the types of neurons based on their functions we can divide a neurons into different types. First one, sensory neurons. They receive a nerve impulses from receptors and it is transmitted to the central nervous system. Since they are originating from the

00:42:50 sense organs or receptors, they are known as sensory neurons and they are carrying these impulses, nerve impulses to the central nervous system. So it is known as aerent neurons. The second category that is known as motor neuron. They carry impulses from central nervous system to muscles and glands, peripheral glands. From the central nervous system, they are carrying the impulses to the muscles or even glands. They are known as epherent epherent neuron. In between these two types of neurons there present the third type

00:43:48 that is inter neurons. Indo means in between. So they interconnect the sensory neuron and the motor neuron. Now based on the number of nerve processes again we can divide the neurons into different types. The first category that is uniolar neurons. Uni means single. So they have only one axone but no dendrons. So it has only one branch towards only one direction one pole. It is only an axon no dendron. So such type of neurons that is known as unipolar neurons. Normally these uniolar neurons are seen

00:44:46 in the embryos not in the adult humans. In humans there are pseudo unipolar neurons. Now the second category that is bipolar neurons. By means two. They have a one axon and one dendron. Hence it is known as bipolar neurons. Now where they are seen located in the body? They are seen located in the retina of eye eyeball and in the old factory epithelium. Now the third category that is known as multi-olar neurons they have many dendrons and only one axone multipolar in different directions the branches are

00:45:53 originating but axon only one and they have a so many dendrons hence it is known as multipolar neurons. where they are seen in the human body. They are mainly seen in the cerebral cortex. Now what are these neurog cells? I have already told you nervous tissue is not only made up of neurons. Here the second category of cell that is neurogle cells. These are known nervous cells which are seen in between the neurons. Then for what purpose they are seen here in between the neurons. What is their significance? They are meant for

00:46:51 protection. Similarly, they will give support, mechanical support and they provide nutrition to the neurons and they are commonly known as gas cells. The second the third category that is ependimal cells. This refers to epithelial cells that lines the cerebral ventricles. Now what is ventricle? Cerebral ventricle the small chambers seen inside the cerebral hemispheres. So cerebral ventricles that are lined by epithelial tissue that special epithelial tissue it is known as ependimal cells. Neuros secrettory

00:47:49 cells doing the function secretion. These are the special type of neurons seen in the hypothalamus of the brain which will secrete some of the hormones and these hormones are known as neuro hormones. So this particular cell that present in the hypothalamus and it will secrete the neuro hormones and such cells are known as neuro secrettory cells. Now coming to connective tissue it is misodermal in origin originated from the middle layer. Cells are normally arranged very loosely with intercellular spaces in

00:48:46 between them and they have abundant amount of matrix. They interlinks the different tissues of the body together. Hence they are known as connective tissue. Now coming to the types of connective tissue. The first category is loose connective tissue. Second is dense connective tissues. The third one that is specialized connective tissue. So different types three different types loose connective tissue dense connective tissues and specialized connective tissues. Coming to the first category loose

00:49:42 connective tissue matrix is semifluid in nature and cells and fibers are arranged loosely here in the matrix. Hence it is known as loose connective tissue. Example areolar tissue and the adipose tissues. So these tissues are aerolar and adipose tissues are the typical examples of loose connective tissue. The term loose connective tissue means cells and fibers are arranged loosely here in the semifluid matrix. Here the first category areolar connective tissue. You can see the diagram here. It is seen under the skin. Aerolar

00:50:43 connective tissue commonly they are seen under the skin. They are seen around the visceral organs, internal organs and they are seen on the walls of blood vessels. It is known as binding tissue. It contains different types of cells such as fibrolast cells, macrofasages and mast cells. Here you can see the diagram also. Here again clearly you can visualize aolar connective tissue with the master cells. These are the cells macrofasages. Then uh here you can see the fibroite and there are different types

00:51:46 of fibers such as collagen fibers and elastin fibers. These dots indicates the semifluid matrix. So here you can see the cells are arranged loosely. Hence it is a loose connective tissue. Now fibrolast or fibroite larger cells oval in shaped and they will secrete the fibers. They will produce collagen and elastin fibers made up of proteins collagen and elastin. Now the second category that is macrofage macrofase cells there another name is hysteocite amibboidal cells irregularly shaped one large one amiioidal in

00:52:49 shape and they help in fagosytosis eating away the foreign particles. The third category of cell that is the mast cell. Large cell, oval in shape or even round in shape and they are secretreting the matrix. Similarly, they secrete the anti-coagulant heparin serotonin and histamine. They help in secretreting three components heparin, serotonin and histamine. Aerial connective tissue it contains fibers. I have already told you collagen fibers as well as elastin fibers. Two different types of fibers

00:53:45 you can see here. Now what are the different types of fibers? Collagen fibers longer. You can see here in the diagram they are longer one, thicker one, unbranched one seen in groups of bundles and are arranged parallelly and they are made up of protein collagen. Their another name is yellow fibers. They help it to strengthen the structure and they help in repair. Now coming to the white fibers. Uh coming to the yellow fibers that is known as elastin fibers. You can see here yellow fiber or elastin thin

00:54:30 and highly branched one made up of protein elastin. They are seen singly and they contributed to elasticity. Now what are the differences between these two fibers? Just you can see the differences. Collagen fibers are white fibers and elastin fibers are known as yellow fibers. Collagen fibers are unbranched. Elastin fibers are branched. Collagen fibers non-elastic. Elastin fibers are elastic. Collagen fibers seen in bundles. And here elastin fibers in singly made up of collagen protein. And here it is made up

00:55:19 of elastin protein and they give tensile strength and they are meant for elasticity. Now think over to some of these questions. Name the different cell junctions found in tissues. Name the cells that makes adipos tissue. To which category does the tendons and ligaments comes under? What are neuroglear cells give their functions? Which type of epithelium is seen in the urinary bladder and why? Which type of epithelial cells are seen in the fallopian tubes and bronchules? Thank you.