Muscular tissue Questions in English

(D) Smooth muscle fibers are spindle-shaped,thick in the middle,and thin at both ends.
They are uninucleated (contain a single nucleus) and lack striations.
They are involuntary and under the control of the $ANS$ (Autonomic Nervous System).
Therefore,the statement that they are multinucleated is incorrect,as they are uninucleated.

(C) Cardiac muscles exhibit a combination of properties found in both striated and unstriated (smooth) muscles.
$1$. Like striated (skeletal) muscles,cardiac muscles show cross-striations due to the arrangement of thick and thin protein filaments ($actin$ and $myosin$).
$2$. Like unstriated (smooth) muscles,cardiac muscles are involuntary in nature,meaning they are not under conscious control.
$3$. These muscles perform rhythmic contractions throughout life under the regulation of the $ANS$ (Autonomic Nervous System).

(B) Striped (skeletal) muscle fibres are cylindrical and multinucleated. The presence of many nuclei in a single cell is known as a syncytium or coenocyte. Therefore,the correct option is $(b)$.

(B) Smooth muscle fibres are characterized by the following features:
$1$. Shape: They are spindle-shaped (fusiform) with tapered ends.
$2$. Striations: They are non-striated,meaning they lack the alternating light and dark bands seen in skeletal or cardiac muscles.
$3$. Nucleus: They are uninucleate,containing a single nucleus located in the center of the cell.
$4$. Control: They are involuntary,meaning their contraction is not under conscious control.
$5$. Branching: They are unbranched.
Therefore,the correct description is spindle-shaped,unbranched,non-striated,uninucleate,and involuntary.

(B) The correct answer is $B$.
Muscular tissue is considered the most abundant tissue in the human body.
There are approximately $639$ muscles in the body,which constitute the bulk of the body mass.
Muscles account for about $40\%$ of the total body weight and $50\%$ of the soft parts of the body.

(A) Smooth muscle fibres are covered by a plasma membrane,but they lack the specialized,distinct connective tissue sheath known as the sarcolemma that is characteristic of striated muscle fibres. While both have a plasma membrane,the term $sarcolemma$ is specifically used to describe the plasma membrane of striated muscle fibres. Therefore,in the context of comparative histology,smooth muscle fibres are often described as lacking the specialized $sarcolemma$ found in striated muscles.

(D) Unstriated muscles,also known as smooth muscles or involuntary muscles,are found in the walls of hollow visceral organs.
$1$. They are present in the walls of blood vessels like veins and arteries to regulate blood flow.
$2$. They are also found in the walls of the uterus,where they play a crucial role during childbirth.
$3$. Since they are present in all the mentioned structures,the correct answer is $D$.

(A) Striated muscles are skeletal muscles,which appear striped under the microscope due to the arrangement of actin and myosin filaments.
These muscle fibers are cylindrical in shape,unbranched,and multinucleated (syncytial).
Therefore,the set that clearly identifies striated muscles is cylindrical,syncytial,and unbranched.

(D) Muscular tissue is primarily classified into three types based on their structure and function:
$1$. Skeletal muscle (Striated/Striped muscle): These are attached to bones and are under voluntary control.
$2$. Smooth muscle (Unstriated/Unstriped muscle): These are found in the walls of internal organs and are under involuntary control.
$3$. Cardiac muscle: These are specialized muscles found only in the heart,which are involuntary and striated.

(C) syncytium is a single cell or cytoplasmic mass containing several nuclei,formed by fusion of cells or by division of nuclei.
$1$. Skeletal muscle fibers are multinucleated (syncytial) because they are formed by the fusion of many myoblasts.
$2$. Cardiac muscle fibers are branched and connected by intercalated discs,which allow them to function as a functional syncytium.
$3$. Smooth muscle cells are uninucleated and do not form a syncytium.
$4$. Therefore,smooth muscle is not syncytial.

(D) Muscular tissues are specialized tissues in animals that possess the unique property of contractility.
These tissues are composed of muscle fibers that can shorten and relax,which generates the force required for the locomotion of the organism and the movement of various internal organs.
Therefore,muscular tissues are primarily responsible for all types of movements in metazoans.

(D) Cardiac muscle tissue is a contractile tissue present only in the heart.
These muscle fibres are striated due to the presence of alternating light and dark bands.
They are branched,which allows the muscle fibres to form a network,facilitating coordinated contraction of the heart.
They are involuntary in nature,meaning their contraction is not under the conscious control of the individual.
Therefore,cardiac muscle is composed of striated,branched,and involuntary muscle fibres.

(A) The movement of food in the stomach is controlled by involuntary actions.
These movements are mediated by smooth muscles,which are also known as unstriated or visceral muscles.
Unlike striated muscles,which are under voluntary control,unstriated muscles function automatically to facilitate peristalsis in the digestive tract.

(C) Unstriated or smooth muscles are involuntary muscles that do not show striations under a microscope.
They are found in the walls of hollow visceral organs such as the alimentary canal,blood vessels,and the urinary bladder.
The pylorus is the opening from the stomach into the small intestine,which is guarded by a sphincter made of smooth muscle.
Therefore,the pylorus is the correct location for unstriated involuntary muscles.
The diaphragm and eyelid contain skeletal muscles (voluntary),and the external ear is composed of cartilage.

(A) The correct answer is $A$.
Fascia is a thin layer of connective tissue that surrounds and holds muscles,blood vessels,nerves,and organs in place.
It provides structural support and allows for the smooth movement of muscles against each other.
Peritoneum is the serous membrane lining the abdominal cavity.
Ligaments connect bone to bone.
Tendons connect muscle to bone.

(B) During embryonic development,the three germ layers are formed: Ectoderm,Mesoderm,and Endoderm.
Skeletal muscles,along with the circulatory system,bones,and dermis of the skin,are derived from the Mesoderm germ layer.
Therefore,the correct answer is Mesoderm.

(C) The term 'low blood supply' or 'hypovascularity' refers to tissues that have a relatively lower density of blood capillaries compared to highly metabolic tissues like the heart.
$1$. Cardiac muscles are highly vascularized to meet their constant demand for oxygen and nutrients.
$2$. Skeletal muscles have a moderate to high blood supply depending on their activity.
$3$. Smooth muscles,which are found in the walls of hollow organs (like the digestive tract or blood vessels),generally have a lower blood supply compared to cardiac or skeletal muscles.
Therefore,smooth muscle is the correct answer.

(D) Smooth muscle fibers are characterized by the following features:
$1$. They are fusiform (spindle-shaped) in structure,tapering at both ends.
$2$. They are unbranched and involuntary,meaning they are not under conscious control.
$3$. Each fiber contains a single,centrally located nucleus (uninucleate).
Therefore,all the given options are correct.

(C) Smooth muscles,also known as involuntary or non-striated muscles,are found in the walls of hollow visceral organs. While they are present in the intestine,stomach,and urinary bladder,the uterus is specifically noted for containing the longest smooth muscle fibers in the human body,especially during pregnancy where they undergo significant hypertrophy and hyperplasia. Therefore,among the given options,the uterus is the most appropriate answer for the location of 'long' smooth muscles.

(B) Skeletal muscles are derived from the embryonic mesoderm.
During embryonic development,the mesoderm differentiates into various tissues,including muscles,bones,and the circulatory system.
Therefore,the correct option is $B$.

(C) In vertebrates,the development of the embryo involves three primary germ layers: the ectoderm,the mesoderm,and the endoderm.
$1$. The ectoderm gives rise to the nervous system,epidermis,and associated structures.
$2$. The endoderm forms the epithelial lining of the digestive tract and respiratory system.
$3$. The mesoderm is responsible for the formation of the skeletal system,muscular system (including skeletal muscles),circulatory system,and excretory system.
Therefore,skeletal muscles are derived from the mesoderm.

(A) : Smooth muscle fibres are elongated and spindle-shaped (fusiform).
Each fibre contains a single oval nucleus surrounded by cytoplasm (sarcoplasm).
In the cytoplasm,myofibrils are arranged longitudinally.
These fibres lack striations and are involuntary in nature,meaning they are not under conscious control.

(C) The correct match is $(c)$ Smooth muscle - Wall of intestine.
$1$. Transitional epithelium is found in the urinary bladder and ureters, not the tip of the nose. The tip of the nose consists of elastic cartilage.
$2$. The lining of the stomach is composed of simple columnar epithelium, not cuboidal epithelium.
$3$. Smooth muscles are found in the walls of internal organs like the stomach, intestine, and blood vessels. They are responsible for involuntary movements like peristalsis in the intestine.
$4$. Tendons are composed of dense regular connective tissue, specifically white fibrous connective tissue, not areolar tissue.

(C) is the correct answer. Smooth muscles are known as involuntary muscles because their action is controlled by the autonomic nervous system,meaning they are not under the conscious control of the organism. The iris of the eye consists of involuntary smooth muscles. While the abdominal wall also contains smooth muscles,the biceps of the upper arm are composed of skeletal muscles,and the heart wall consists of specialized cardiac muscles.

(D) The characteristics described are as follows:
$1$. Location: They are found in the inner walls of hollow visceral organs like the alimentary canal.
$2$. Appearance: They are non-striated (smooth) and spindle-shaped (fusiform).
$3$. Control: They are involuntary,meaning they are not under conscious control.
$4$. Innervation: They are controlled by the autonomic nervous system.
These features are characteristic of smooth muscles,which are also known as visceral muscles. Therefore,the correct option is $D$.

(A) Smooth muscle fibers are fusiform or spindle-shaped,meaning they taper at both ends.
They do not possess striations (light and dark bands),which is why they are called non-striated or smooth muscles.
In contrast,skeletal and cardiac muscles are striated.

(A) Muscle tissue is responsible for movement and locomotion in the body.
It consists of specialized cells called muscle fibers that have the ability to contract and relax.
This contractile property allows the body to adjust to environmental changes and maintain posture by keeping various body parts in their correct positions.

(A) Smooth muscle tissue,also known as involuntary or non-striated muscle,consists of cells that are fusiform (spindle-shaped) in structure.
These cells are unbranched and possess a single central nucleus (uninucleate).
They lack the striations (light and dark bands) found in skeletal or cardiac muscles.
Their contraction is controlled by the autonomic nervous system,making them involuntary in nature.
Therefore,the correct characteristics are fusiform,unbranched,non-striated,uninucleate,and involuntary.

(D) $1$. Areolar tissue is a loose connective tissue found beneath the skin,not in tendons (tendons consist of dense regular connective tissue).
$2$. Pseudostratified epithelium is typically found in the trachea and bronchi,not the surface of the nose.
$3$. Cuboidal epithelium is found in kidney tubules and ducts of glands,whereas the stomach lining consists of columnar epithelium.
$4$. Smooth muscle tissue is involuntary and is found in the walls of hollow internal organs such as the stomach,blood vessels,and the intestine. Thus,$D$ is the correct match.

(D) The human body contains three types of muscle tissues: skeletal,smooth,and cardiac.
$1$. The heart wall is composed of cardiac muscle,which is striated and involuntary.
$2$. The biceps of the upper arm are skeletal muscles,which are striated and voluntary.
$3$. The abdominal wall contains skeletal muscles for voluntary movement and support.
$4$. The iris of the eye contains smooth muscles,which are involuntary and responsible for controlling the size of the pupil.

(C) Smooth muscle tissue (also known as visceral muscle) is characterized by the following features:
$1$. It is involuntary,meaning it is not under conscious control.
$2$. The cells are fusiform (spindle-shaped) in structure.
$3$. It is non-striated (smooth) because it lacks the regular arrangement of actin and myosin filaments found in skeletal muscle.
$4$. Each cell contains a single nucleus (uninucleate).
Therefore,the correct description is involuntary,fusiform,and non-striated.

(A) Cardiac muscle cells are short,cylindrical cells joined end-to-end and by side branching to form a network.
Intercalated discs are the dense junctions formed between cardiac muscle cells where they meet each other.
These discs are specialized regions of the cell membranes that allow the rapid transmission of electrical impulses.
Since cardiac muscle possesses considerable rhythmicity and generates its own wave of excitation,these discs function as boosters for the muscle contraction wave,ensuring that the heart contracts as a single unit (syncytium).

(N/A)

Cardiac muscles	Striated muscles
$(1)$ They are involuntary in function.	$(1)$ They are voluntary in function.
$(2)$ They are uninucleate and branched.	$(2)$ They are multinucleate and unbranched.
$(3)$ They are found only in the heart.	$(3)$ They are found attached to bones in limbs.

(N/A) $ \Rightarrow $ Muscle tissue is associated with the movements of the organs of the body.
$ \Rightarrow $ Each muscle is made of many long, cylindrical fibres arranged in parallel arrays.
$ \Rightarrow $ These fibres are composed of numerous fine fibrils called myofibrils.
$ \Rightarrow $ All muscle fibres contract (shorten) in response to stimulation, then relax and return to their uncontracted state in a coordinated fashion.
$ \Rightarrow $ Their action moves the body to adjust to the changes in the environment and to maintain the positions of the various parts of the body.
$ \Rightarrow $ In general, muscles play an active role in all the movements of the body.
$ \Rightarrow $ Types of muscle tissue:
Muscles are of three types:
$ (i) $ Skeletal muscle tissue
$ (ii) $ Smooth muscle tissue
$ (iii) $ Cardiac muscle tissue
$ (i) $ Skeletal muscle tissue: These are closely attached to skeletal bones. In a typical muscle such as the biceps, striated (striped) skeletal muscle fibres are bundled together in a parallel fashion. $ A $ sheath of tough connective tissue encloses several bundles of muscle fibres.
$ (ii) $ Smooth muscle tissue:
$ \Rightarrow $ Location: The wall of internal organs such as the blood vessels, stomach, and intestine contains this type of muscle tissue.
$ \Rightarrow $ Structure: Each cell is spindle-shaped and has a nucleus in its central broader part. Dark and light bands are not seen in it.
$ \Rightarrow $ They are involuntary in action.
$ (iii) $ Cardiac muscle tissue:
$ \Rightarrow $ Location: This muscle is present only in the wall of the heart.
$ \Rightarrow $ Structure: Cardiac muscle cells are branched and cylindrical. They contain one or two nuclei arranged in the centre.
$ \Rightarrow $ They possess intercalated discs at the ends of the cells, which function as communication junctions. They are involuntary and show rhythmic contraction.

(N/A)

Skeletal muscle	Cardiac muscle
$(1)$ The cells are unbranched.	$(1)$ The cells are branched.
$(2)$ Intercalated disks are absent.	$(2)$ Intercalated disks are present,which help in the synchronization of heartbeats.
$(3)$ Alternate light and dark bands are prominent.	$(3)$ Faint bands are present.
$(4)$ They are voluntary muscles.	$(4)$ They are involuntary muscles.
$(5)$ They contract rapidly and get fatigued easily.	$(5)$ They contract rhythmically and do not get fatigued.
$(6)$ They are attached to bones.	$(6)$ They are present only in the heart.

(N/A) Muscle tissue is primarily responsible for movement in the body. Its key functions include:
$1$. Movement: Muscle tissue enables voluntary movements (like walking or lifting objects) and involuntary movements (like the beating of the heart or peristalsis in the digestive tract).
$2$. Posture Maintenance: Muscles maintain body posture and stabilize joints by providing constant tension.
$3$. Heat Production: Muscle contraction generates heat,which is essential for maintaining body temperature ($37^{\circ}C$ in humans).
$4$. Protection: Muscles provide a protective layer for internal organs and bones.

(N/A) Smooth muscle tissue is a type of non-striated,involuntary muscle found in the walls of hollow internal organs such as the stomach,intestines,blood vessels,and urinary bladder.
$1$. Structure: The cells are fusiform (spindle-shaped) and taper at both ends. They do not show striations,hence the name 'smooth'. Each cell contains a single,centrally located nucleus.
$2$. Function: These muscles are involuntary,meaning they are controlled by the autonomic nervous system and are not under conscious control.
$3$. Characteristics: They contract slowly and can remain contracted for long periods without fatigue. They are held together by cell junctions and bundled together in a connective tissue sheath.

(N/A)

Non-striated muscle	Striated muscle
$(1)$ It is also called smooth muscle.	$(1)$ It is also called skeletal muscle.
$(2)$ They are composed of spindle-shaped cells having a single nucleus.	$(2)$ It is made up of multinucleated,long,cylindrical cells.
$(3)$ They are involuntary.	$(3)$ They are voluntary.
$(4)$ They are located in internal organs.	$(4)$ They are connected to bones.
$(5)$ They do not get tired quickly.	$(5)$ They get tired quickly.

(A) $(i)$ Location: Cardiac muscular tissue.
$\Rightarrow$ Function: These are communication junctions that allow the cells to contract as a unit by transmitting signals for contraction.
$(ii)$ Location: Inside Red Blood Cells $(RBCs)$.
$\Rightarrow$ Function: It acts as a respiratory pigment responsible for the transport of $O_{2}$ and $CO_{2}$ in the blood.

(N/A) The cardiac muscle tissue present in the heart has the following special characteristics:
$(1)$ Cardiac muscle fibers are involuntary,meaning they do not function according to our will.
$(2)$ These muscles are fatigue-resistant and exhibit rhythmicity.
$(3)$ They have a rich blood supply.
$(4)$ They are myogenic,meaning they can generate their own electrical impulses for contraction even when removed from the body. They possess properties of both muscle and nerve tissue.

(N/A) $\Rightarrow$ Location: The walls of internal organs such as blood vessels,stomach,and intestine contain this type of muscle tissue.
$\Rightarrow$ Structure: Each cell is spindle-shaped and has a nucleus in its central broader part.
$\Rightarrow$ Sarcolemma: The sarcolemma is indistinct. Dark and light bands (striations) are not observed.
$\Rightarrow$ Myofibrils: There is no regular arrangement of myofibrils.
$\Rightarrow$ Sarcoplasm: Granular sarcoplasm surrounds the nucleus,while the remaining cytoplasm contains a large number of minute myofibrils.
$\Rightarrow$ Organization: They are bundled together in a connective tissue sheath.
$\Rightarrow$ Function: The contraction and relaxation of smooth muscle tissue are not rapid. They are involuntary in action; hence,they are called involuntary muscles.
$\Rightarrow$ Fatigue: Their contraction and relaxation occur at a very slow speed and persist for a longer period,so they do not get fatigued easily.

(N/A) Cardiac muscle tissue is a contractile tissue present only in the heart.
$1$. Structure: Cardiac muscle cells are cylindrical,branched,and uninucleated (or sometimes binucleated),with the nucleus located centrally.
$2$. Striations: These muscles are striated,meaning they possess alternating dark and light bands ($A$ and $I$ bands) similar to skeletal muscles.
$3$. Intercalated Discs: $A$ unique feature of cardiac muscle is the presence of intercalated discs at the junctions between adjacent cells. These are specialized cell junctions that allow the cells to contract as a single unit by facilitating rapid communication through gap junctions.
$4$. Connective Tissue: The intercellular spaces are filled with loose connective tissue (endomysium) containing a network of collagen fibers.
$5$. Function: They are involuntary in nature and contract rhythmically throughout life without fatigue.

(B) Based on the provided figures:
$A$ represents skeletal muscle,which is characterized by long,cylindrical,multinucleated,and striated fibres.
$B$ represents smooth muscle,which consists of spindle-shaped,uninucleated,and non-striated fibres.
$C$ represents cardiac muscle,which consists of branched,striated,and uninucleated fibres with intercalated discs.
Therefore,the correct identification is $A$ - Skeletal muscle,$B$ - Smooth muscle,$C$ - Cardiac muscle.

(B) Muscle tissue plays a vital role in providing movement and heat generation to the organs of the body.
Muscle cells are specialized for contractility,which is the ability to shorten,and relaxation,which is the ability to return to their original length.
Therefore,muscle cells are specialized in contraction and relaxation.

(D) The cells of smooth muscle tissue are fusiform (spindle-shaped) and pointed at their ends.
Striations are absent in these muscles because the actin and myosin filaments are not arranged in a regular,repeating pattern as they are in striated muscles.
Smooth muscles are involuntary and are found in the walls of internal organs.

(A) Cardiac muscles are involuntary,cross-striated,and non-fatigued fibers.
Cell junctions fuse the plasma membranes of cardiac muscle cells and make them stick together.
Communication junctions,known as intercalated discs,are present at some fusion points.
These discs allow the cells to contract as a single unit; when one cell receives a signal to contract,its neighboring cells are also stimulated to contract.

(D) Smooth muscle is an involuntary,spindle-shaped,uninucleated,tapering,and non-striated muscle.
Smooth muscles are responsible for the contractility of hollow organs,such as blood vessels,the gastrointestinal tract,the bladder,or the uterus.
Their structure differs significantly from that of skeletal muscle,although they can develop isometric force per cross-sectional area equal to that of skeletal muscle.

(B) The smooth muscle fibres are involuntary,taper at both ends (fusiform shape),and do not show striations under a microscope.
They are found in the walls of internal organs such as the blood vessels,stomach,and intestine.
Since their function cannot be directly controlled by our will,they are termed 'involuntary' muscles.

(B) The statements describe the characteristics of cardiac muscle tissue.
$(i)$ Cardiac muscle is a contractile tissue present exclusively in the heart.
$(ii)$ Cell junctions (intercalated discs) fuse the plasma membranes of cardiac muscle cells,ensuring they remain firmly attached.
$(iii)$ Communication junctions (gap junctions) at these fusion points allow the cells to contract as a single unit (syncytium). When one cell receives a signal to contract,the electrical impulse spreads rapidly to neighboring cells,stimulating them to contract simultaneously.
Therefore,the correct option is $B$.

(C) Intercalated discs are a unique and distinguishing feature of cardiac muscle. They are dark,irregular,zig-zag partitions found between adjacent cardiac muscle cells. They consist of both transverse and lateral portions. Intercalated discs provide firm adhesions between adjacent cells and facilitate electrical coupling for the rapid spread of excitation,which allows the heart muscle to contract as a single unit.