Epithelial tissue Questions in English

(A) The stratified squamous epithelium consists of multiple layers of cells. Its primary function is protection against mechanical and chemical stress. It is found in regions that are subject to wear and tear,such as the pharynx,esophagus,and the skin (epidermis).

(D) Epithelial tissue is characterized by the following features:
$1$. The cells are compactly packed with very little intercellular matrix ($a$ and $b$ are correct).
$2$. It forms a covering or lining for some parts of the body.
$3$. Based on the number of layers,it is classified as simple (single-layered) or compound (multi-layered) epithelium ($c$ is correct).
Therefore,all the given statements are correct.

(B) The epithelial tissue composed of thin,flat,tile-like cells is known as $Squamous$ epithelium.
These cells have irregular boundaries and are found in walls of blood vessels and air sacs of lungs.
Among the given options,the inner wall of blood vessels (endothelium) is lined by simple squamous epithelium.
The alimentary canal is lined by columnar epithelium,and the fallopian tube is lined by ciliated epithelium.

(B) Sebaceous glands are classified as $Holocrine$ glands. In holocrine glands,the entire secretory cell is destroyed and discharged along with its secretory product. As the cells of the sebaceous gland mature,they accumulate lipids,rupture,and the entire cell content is released as sebum.

(D) The salivary glands and the exocrine part of the pancreas are classified as $Merocrine$ glands.
In $Merocrine$ secretion,the secretory products are released via exocytosis from secretory vesicles into the duct,without any loss of cellular cytoplasm or damage to the cell itself.
This is the most common mode of secretion in the human body.

(D) The basement membrane is a thin,fibrous,extracellular matrix of tissue that separates the lining of an internal or external body surface from underlying connective tissue. It is not composed of cells (epidermal or endodermal) themselves; rather,it is a non-cellular layer secreted by the epithelial cells and the underlying connective tissue. Therefore,the correct answer is $(d)$ None of these.

(D) The coelomic epithelium,also known as the mesothelium,lines the coelom (body cavity) in animals. The cells forming this lining are typically flat,thin,and scale-like,which characterizes the squamous epithelium. Therefore,the correct answer is $D$.

(D) Epithelial tissues are characterized by the presence of specialized junctions that provide both structural and functional links between individual cells.
These junctions include tight junctions (which prevent leakage),adhering junctions (which perform cementing to keep neighboring cells together),and gap junctions (which facilitate communication between cells by connecting the cytoplasm of adjacent cells for the rapid transfer of ions,small molecules,and sometimes big molecules).
These specialized junctions are a defining feature of epithelial tissues,allowing them to act as a cohesive barrier.

(A) The basement membrane is a thin,fibrous,extracellular matrix of tissue that separates the lining of an epithelium from underlying connective tissue.
In $Transitional$ $epithelium$ (also known as urothelium),the cells are capable of stretching and changing shape,and a distinct basement membrane is often considered absent or poorly developed compared to other epithelial tissues,as these cells are specialized for distension in organs like the urinary bladder.
In contrast,squamous,columnar,and cuboidal epithelia are typically anchored to a well-defined basement membrane.

(D) $1$. Ciliated epithelium is found in the inner surface of hollow organs like bronchioles and Fallopian tubes. This is a correct pair.
$2$. Compound epithelium is found in the dry surface of the skin and the moist surface of the buccal cavity, pharynx, and inner lining of ducts of salivary glands and pancreatic ducts. Wait, actually, the ducts of salivary glands are lined by simple cuboidal or columnar epithelium, not compound. However, looking at standard $NCERT$, compound epithelium is primarily protective. Let's re-evaluate: Areolar tissue is a loose connective tissue found beneath the skin (subcutaneous layer). Thus, $(d)$ is also a correct description of its location.
$3$. Upon closer inspection of $NCERT$: Compound epithelium is found in the ducts of salivary glands and pancreatic ducts. So $(b)$ is correct.
$4$. Areolar tissue is present beneath the skin. So $(d)$ is correct.
$5$. Wait, the question asks for the incorrect pair. Let's re-verify: $(a)$ is correct. $(b)$ is correct. $(c)$ is correct. $(d)$ is correct. Actually, in many competitive contexts, 'Areolar tissue' is described as being present 'beneath the skin', not 'in the skin'. If the question implies $(d)$ is incorrect because it is 'beneath' rather than 'in', then $(d)$ is the answer.

(A) The secretory portion of sweat glands is lined by cuboidal epithelium.
Cuboidal epithelium consists of cube-like cells and is primarily involved in secretion and absorption.
It is commonly found in the ducts of glands and the tubular parts of nephrons in the kidneys.

(D) The vagina is lined by a stratified squamous epithelium.
This type of epithelium consists of multiple layers of cells,where the cells at the free surface are flattened (squamous).
This structure provides protection against mechanical abrasion,which is necessary for the vaginal lining during various physiological processes.

(C) Merocrine glands are those in which the secretory product is released via exocytosis without any loss of cellular material.
Salivary glands are the classic example of merocrine glands.
Sebaceous glands are holocrine glands,while mammary glands are apocrine glands.

(C) The inner lining of the stomach and the alimentary canal (intestine) is composed of $Simple \ columnar \ epithelium$.
This tissue consists of a single layer of tall, slender cells with nuclei located at the base.
Its primary function is secretion and absorption, which is essential for the digestive tract.
While the liver is a glandular organ, the epithelial lining of the digestive tract itself is characteristically columnar.

(A) Ciliated epithelium consists of cells that bear cilia on their free surfaces.
These cilia move particles or mucus in a specific direction over the epithelium.
In the human body,ciliated epithelium is primarily found in the inner surface of hollow organs like the bronchioles and the trachea (windpipe) to help move mucus and trapped dust particles out of the respiratory tract.
Therefore,the correct option is $A$.

(D) Ciliated epithelium consists of cells that bear cilia on their free surface.
These cilia move particles or mucus in a specific direction over the epithelium.
They are primarily present in the inner surface of hollow organs like the bronchioles,trachea,and the fallopian tubes (oviducts).
In the fallopian tubes,they help in the movement of the ovum.
In the trachea and bronchioles,they help in moving mucus and trapped dust particles out of the respiratory tract.
Therefore,since they are found in both the fallopian tubes and the trachea,the correct answer is 'All of the above'.

(D) Epithelial tissue is characterized by a free surface that faces either a body fluid or the outside environment,thus providing a covering or a lining for some parts of the body. The cells are compactly packed with little intercellular matrix. Epithelial tissue does not form the internal structural parts of organs (like the parenchyma or connective tissue framework); rather,it covers or lines them. Therefore,the statement that it forms internal structural parts of organs is incorrect.

(A) Sweat glands (eccrine glands) are classified as $Merocrine$ glands because they secrete their products via exocytosis without the loss of any cellular material or cytoplasm.
In contrast,$Holocrine$ glands (like sebaceous glands) release their entire cell as a secretion,and $Apocrine$ glands release a portion of the cell.
Therefore,the correct classification for sweat glands is $Merocrine$.

(D) The epidermis of human skin is composed of $Stratified$ $squamous$ $epithelium$.
Specifically, it is a $keratinized$ $stratified$ $squamous$ $epithelium$ that provides a protective barrier against mechanical injury, pathogens, and water loss.
While the dermis beneath it contains connective tissues like $areolar$ and $dense$ $irregular$ $connective$ $tissue$, the epidermis itself is epithelial in nature.

(D) tissue is defined as a group of cells having a common embryonic origin and usually performing a common function. This structural and functional organization allows the cells to work together efficiently to perform specific tasks within an organism. Therefore,the correct definition of a tissue emphasizes both its developmental origin and its functional role.

(A) In biological organization, cells are the basic structural and functional units of life. When a group of cells, which are similar in structure and origin, work together to perform a specific function, they are collectively known as a $Tissue$. Multiple tissues then organize to form an $Organ$, and various organs work together to form an $Organ \text{ } system$.

(A) In biological organization,cells are the fundamental units of life.
When cells that are similar in structure and perform a specific,common function group together,they form a tissue.
Therefore,the correct answer is tissue.

(A) Melanin is a pigment produced by specialized cells called melanocytes. It is responsible for the pigmentation of skin,hair,and eyes in humans. While it is often classified as a pigment,it is a complex polymer derived from the amino acid tyrosine and is associated with protein structures in the body. Among the given options,Melanin is the correct answer regarding body coloration.

(B) Scales,feathers,hair,nails,and the outer layer of skin in vertebrates are composed of $Keratin$. $Keratin$ is a fibrous,structural,and insoluble protein that provides protection and mechanical strength to these tissues. Myosin and Actin are contractile proteins found in muscles,while Melanin is a pigment responsible for skin and hair color.

(A) Melanin is the primary pigment responsible for skin color in humans. It is produced by specialized cells called melanocytes located in the epidermis of the skin. Melanin helps protect the skin from harmful ultraviolet $(UV)$ radiation by absorbing it. Actin and myosin are contractile proteins found in muscle cells,while hemoglobin is the oxygen-carrying protein found in red blood cells.

(C) In biological hierarchy,a tissue is defined as a group of cells having a common origin,similar structure,and performing a specific function. Therefore,a tissue is formed by the organization of cells. Since a tissue is essentially a group of cells working together,both options $(A)$ and $(B)$ describe the components involved in the formation of a tissue. Thus,the correct answer is $(C)$.

(D) Biological organization refers to the hierarchy of complex biological structures and systems that define life.
$1$. Subatomic particles,atoms,and molecules are chemical levels of organization,not biological.
$2$. Tissues are formed by a group of cells performing a specific function,which represents a fundamental level of biological organization.
Therefore,the correct option is $D$.

(D) : Most cells in animal tissues (with the exception of a few terminally differentiated cells such as skeletal muscle cells and blood cells) are in communication with their adjoining cells via gap junctions.
At the place where a gap junction is present,the membranes of two adjacent cells are separated by a uniform narrow gap of about $2-4 \ nm$.
The gap is spanned by channel-forming proteins called connexins,which allow inorganic ions and other small water-soluble molecules to pass directly from the cytoplasm of one cell to the cytoplasm of another cell.

(C) The correct answer is $C$.
$1$. Inner lining of salivary ducts is lined by simple cuboidal epithelium.
$2$. The moist surface of the buccal cavity is lined by non-keratinized stratified squamous epithelium.
$3$. The tubular parts of nephrons (like proximal convoluted tubule) are lined by cuboidal epithelium.
$4$. The inner surface of bronchioles is lined by ciliated columnar epithelium.

(A) The correct option is $(A)$.
Intestine is lined by glandular epithelium,which is secretory in function.
The glands found in the intestine are exocrine and may be unicellular or multicellular.
When unicellular glands secrete mucus,they are called goblet cells,which are common in the columnar epithelium of the intestine.
Multicellular glands consist of a duct and a secretory portion,both formed of epithelial cells,such as the Crypts of Lieberkuhn and Brunner's glands found in the intestine.

(B) : In humans,ciliated columnar epithelial cells are primarily found in the inner surface of hollow organs like the bronchioles and the Fallopian tubes (oviducts).
These cells possess cilia on their free surface,which help in the movement of particles or mucus in a specific direction.
They are also found in the nasal passages,the ventricles of the brain,and the central canal of the spinal cord in the embryo.

(B) : Simple squamous epithelium is composed of large flat cells whose edges fit closely together like the tiles in a floor,hence it is also called pavement epithelium.
The nuclei of the cells are flattened and often lie at the centre of the cells and cause bulgings of the cell surface.
The epithelium lines the blood vessels,lymph vessels,heart,terminal bronchioles,alveoli of the lungs,walls of the Bowman's capsules,and descending limbs of the loop of Henle.
In the blood vessels and heart,it is specifically called endothelium.

(B) : The ciliated columnar epithelial cells in humans are present in the nasal passages,oviducts (Fallopian tubes),terminal bronchioles,ventricles of the brain,and the central canal of the spinal cord of the embryo. Ciliated epithelium consists of cells that bear cilia on their free surface,which help in the movement of particles or mucus in a specific direction.

(B) : Epithelial tissues consist of variously shaped cells closely arranged in one or more layers.
The cells are held together by intercellular junctions like tight,adhering,and gap junctions.

(D) The correct answer is $D$. Cell junctions are specialized structures that provide contact between neighboring cells or between a cell and the extracellular matrix. They are most abundant in epithelial tissues, which form the lining of various body cavities and surfaces.
$1$. $Ciliated$ $epithelium$ is a type of epithelial tissue consisting of columnar or cuboidal cells. Because epithelial cells are tightly packed to form a continuous barrier, they require various types of cell junctions (such as tight junctions, adherens junctions, and gap junctions) to maintain structural integrity and regulate transport.
$2$. $Thrombocytes$ (platelets) are blood cells involved in clotting and do not form tissue layers with junctions.
$3$. $Tendon$ and $hyaline$ $cartilage$ are types of connective tissue. In connective tissues, cells are typically separated by a large amount of extracellular matrix, and therefore, cell junctions are far less frequent compared to epithelial tissues.

(C) In epithelial tissue,there are three main types of cell junctions that provide structural and functional links between cells:
$1$. Tight junctions: These help to stop substances from leaking across a tissue.
$2$. Adhering junctions: These perform cementing to keep neighboring cells together.
$3$. Gap junctions: These facilitate the cells to communicate with each other by connecting the cytoplasm of adjoining cells,for rapid transfer of ions,small molecules,and sometimes big molecules.
Therefore,the correct answer is $3$.

(B) The provided figure illustrates a glandular epithelium structure.
Specifically,it shows a cluster of cells forming a secretory unit,which is characteristic of a multicellular gland.
In a multicellular gland,the secretory cells are arranged in a cluster or a pocket-like structure,as indicated by label $A$.
Therefore,$A$ represents a multicellular gland.

(D) The characteristics described are:
$1$. The presence of cilia on the free surface of cells helps in moving particles or mucus in a specific direction over the epithelial surface.
$2$. This tissue is commonly found in the inner surface of hollow organs like the bronchioles and fallopian tubes.
Therefore,the correct tissue is the Ciliated epithelium.

(D) Compound epithelium consists of two or more cell layers and has a protective function in our skin and other organs.
$1$. It is multi-layered,which provides protection against chemical and mechanical stresses.
$2$. It covers the dry surface of the skin and the moist surface of the buccal cavity,pharynx,and inner lining of ducts of salivary glands and pancreatic ducts.
$3$. Due to its multi-layered structure,its role in secretion and absorption is very limited.
$4$. It does not produce hormones. Therefore,the statement that it 'Produces hormone only' is incorrect.

(B) The wall of blood vessels is lined by a single thin layer of flattened cells with irregular boundaries,which is known as the $Squamous$ $epithelium$. This specific type is also referred to as the $endothelium$ in blood vessels. Its primary function is to form a diffusion boundary,facilitating the exchange of substances between the blood and surrounding tissues.

(A) Cuboidal epithelium consists of a single layer of cube-like cells.
It is commonly found in the ducts of glands and the tubular parts of nephrons in the kidneys.
Its main functions are secretion and absorption.
Cartilage is a type of connective tissue,the pharynx is lined with stratified squamous epithelium,and the alveoli are lined with squamous epithelium.

(A) The compound epithelium is made up of more than one layer (multi-layered) of cells.
Because of its multi-layered structure,it has a limited role in secretion and absorption.
Its main function is to provide protection against mechanical and chemical stresses.
Examples include the dry surface of the skin and the moist surface of the buccal cavity.

(A) The lining of the stomach and intestine is composed of columnar epithelium tissue.
This tissue consists of tall and slender cells.
Their nuclei are located at the base.
This type of epithelium is specialized for absorption and secretion,which are the primary functions of the stomach and intestinal lining.

(B) The correct matches are as follows:
$1$. Cuboidal epithelium is found in the ducts of glands $(1-c)$.
$2$. Columnar epithelium is found in the lining of the stomach and intestine $(2-e)$.
$3$. Ciliated epithelium is found on the inner surface of fallopian tubes $(3-b)$.
$4$. Compound epithelium is found on the moist surface of the buccal cavity and pharynx $(4-a)$.
Therefore,the correct sequence is $1-c, 2-e, 3-b, 4-a$.

(D) Epithelial tissue is the type of animal tissue that forms the outer covering of the body and the lining of internal organs and cavities.
It acts as a protective barrier against mechanical injury,pathogens,and dehydration.
Connective tissue supports and binds other tissues.
Muscular tissue is responsible for movement.
Neural tissue is responsible for the control and coordination of body activities.

(C) The correct statement is $C$.
$1$. Columnar epithelium cells have nuclei located at the base,not the top,and are found in the lining of the stomach and intestine.
$2$. Squamous epithelium cells have irregular boundaries and a flattened nucleus,not a small nucleus with regular boundaries.
$3$. Cuboidal epithelium consists of cube-like cells arranged in a single layer,commonly found in the ducts of glands and tubular parts of nephrons in kidneys.
$4$. Cuboidal epithelium cells are cube-shaped,not flattened (flattened cells are characteristic of squamous epithelium),and while they are found in the thyroid gland,the description of them being 'flattened' is incorrect.

(B) The provided figure shows a tissue composed of more than one layer of cells,which is characteristic of compound epithelium.
Compound epithelium is made up of more than one layer (multi-layered) of cells and thus has a limited role in secretion and absorption.
Their main function is to provide protection against chemical and mechanical stresses.
The label '$a$' points to the multiple layers of cells present in the tissue.
Therefore,the correct identification is Compound epithelium - multilayered cells.