16 Most VSAQ’s of Structural Organisation in Animals Chapter in Inter 1st Year Zoology (TS/AP)

2 Marks

VSAQ-1 : What is cephalization? How is it useful to its possessors?

Cephalization is the development of a distinct head region in animals with bilateral symmetry. It is useful to possessors because it concentrates nerve cells and sensory organs, enhancing environmental perception and movement efficiency. This, in turn, leads to complex behaviors that aid in survival and reproductive success.

VSAQ-2 : Mention the animals that exhibited a ‘tube-within-a-tube’ organisation for the first time? Name their body cavity.

  1. The animals that first exhibited a ‘tube-within-a-tube’ organization are Nematoda (roundworms).
  2. Their body cavity is known as a Pseudocoelom.

VSAQ-3 : Why is the true coelom considered a secondary body cavity?

The true coelom is considered a secondary body cavity because it develops later in the embryonic stage from the mesoderm, replacing the blastocoel, which serves as the primary body cavity during early development. This replacement of the blastocoel with the true coelom designates it as the secondary body cavity in eucoelomate animals.

VSAQ-4 : What are retroperitoneal organs?

Retroperitoneal organs are vertebrate organs, like the kidneys, which are covered by the parietal peritoneum only on their ventral side. The term “retroperitoneum” denotes the space located behind the peritoneum, and organs situated in this space are termed retroperitoneal organs.

VSAQ-5 : What is Enterocoelom? Name the enterocoelomate phyla in the animal kingdom?

  1. Enterocoelom is a true coelom that originates from the mesodermal outpouching of the archenteron during embryonic development.
  2. The enterocoelomate phyla in the animal kingdom include Echinodermata, Hemichordata, and Chordata.

VSAQ-6 : Distinguish between endocrine and exocrine glands with examples.

Endocrine Glands

  1. Ductless glands.
  2. Secrete hormones directly into the bloodstream.
  3. Examples: Pituitary gland, Thyroid gland.

Exocrine Glands

  1. Glands with ducts.
  2. Secrete substances like saliva, mucus, and digestive juices.
  3. Examples: Salivary glands, Mucus glands.

VSAQ-7 : Mention any two substances secreted by mast cells and their functions.

Two substances secreted by mast cells are:

  1. Histamine: Histamine is released during allergic reactions and plays a crucial role in causing symptoms such as inflammation, itching, and increased blood flow to affected areas.
  2. Heparin: Heparin is an anticoagulant that prevents blood from clotting too quickly. It is released by mast cells to prevent the formation of clots in the blood vessels near the site of an injury or inflammation.

VSAQ-8 : Distinguish between a ligament and a tendon.


  1. Connects bone to bone.
  2. Provides joint stability.
  3. Limits joint movement.
  4. Made of fibrous tissue.


  1. Connects muscle to bone.
  2. Transmits muscle force to move bones.
  3. Enables precise movement.
  4. Also made of fibrous tissue, but more elastic.

VSAQ-9 : What is the Strongest Cartilage? In Which regions of the human body, do you find it?

The strongest type of cartilage is called fibrous cartilage, and it is found in two regions of the human body:

  1. Intervertebral Discs: These are located between the vertebrae of the spine.
  2. Pubic Symphysis of the Pelvis: Fibrous cartilage forms the cartilaginous connection between the two pubic bones.

VSAQ-10 : Define osteon.

An osteon, also referred to as the Haversian system, is a structural unit present in compact bone. It comprises a central Haversian canal, which is encircled by concentric layers of lamellae and lacunae. Within the Haversian canal are blood vessels, nerves, and connective tissue, forming a vital transport system for nutrients and waste products within dense bone tissue. Osteons play a pivotal role in enhancing the strength and stability of compact bone in the human body.

VSAQ-11 : What is a Sesamoid bone? Give an example.

A sesamoid bone is a small, rounded bone that develops within a tendon or near a joint. It forms through a process called ossification, in which bone tissue replaces soft connective tissue.

A prime example of a sesamoid bone is the patella, commonly known as the kneecap, which is located within the tendon of the quadriceps muscle at the front of the knee joint. Sesamoid bones serve to protect tendons from wear and tear and improve the mechanical advantage of the muscle.

VSAQ-12 : What are microglia and what is their origin and add a note on their function.

Microglia are immune cells found in the central nervous system (CNS). They originate from myeloid progenitor cells in the embryonic yolk sac and serve essential functions:

  1. Immune Response: Microglia defend the CNS by phagocytosing pathogens and debris.
  2. Surveillance: They continuously monitor brain tissue for damage or abnormalities.
  3. Maintenance: Microglia help maintain brain health by clearing waste and assisting in neural repair. Dysregulation can lead to neuroinflammatory conditions and neurodegenerative diseases.

VSAQ-13 : What is the haematocrit value?

The haematocrit value, also referred to as packed cell volume (PCV), represents the percentage of the volume of red blood cells (RBCs) within the total volume of blood. Essentially, it measures the proportion of blood that consists of RBCs. This parameter is a crucial component of blood tests and is employed to evaluate various medical conditions, including anemia and dehydration.

VSAQ-14 : What are intercalated discs? What is their significance?

Intercalated discs are specialized structures located in cardiac muscle cells. They manifest as dark lines spanning across cardiac muscle fibers. These discs hold great importance in heart function.

Significance: Intercalated discs contain gap junctions, facilitating rapid and synchronized electrical communication between neighboring cardiac muscle cells. This swift transmission of electrical impulses via intercalated discs ensures the coordinated contraction of heart muscles. This, in turn, leads to an efficient heartbeat and the proper pumping of blood throughout the body, crucial for sustaining life.

VSAQ-15 : “Cardiac muscle is highly resistant to fatigue”. Justify.

Cardiac muscle is highly resistant to fatigue due to specific adaptations:

  1. Abundant Sarcosomes (Mitochondria): Cardiac muscle cells have numerous mitochondria for continuous energy production through aerobic respiration, preventing fatigue.
  2. High Myoglobin Content: Rich myoglobin stores in cardiac muscle provide a stable oxygen reserve, ensuring prolonged aerobic metabolism and sustained contraction.
  3. Rich Blood Supply: A constant blood supply via coronary arteries delivers oxygen and nutrients, supporting continuous energy production and preventing fatigue during prolonged activity. These adaptations allow cardiac muscle to maintain efficient and relentless pumping of blood without tiring easily.

VSAQ-16 : Distinguish between white matter and grey matter of ‘CNS’.

White Matter:

  1. Appears white due to the presence of myelin.
  2. Comprises myelinated nerve fibers.
  3. Functions in transmitting nerve impulses over long distances.

Grey Matter:

  1. Appears grey because of Nissl bodies.
  2. Comprises non-myelinated nerve fibers, dendrites, and cell bodies (cytons).
  3. Functions in information processing, including synaptic connections and integration of signals.