Chapter 7: Structural Organisation in Animals

i) American cockroach

ii) 4 pairs of spermathecae are found in earthworms.

iii) Two ovaries are found lying laterally around the 2^nd to the 6^th abdominal segments.

iv) 10 segments

v) Malpighian tubules are found at the junction of the midgut and the hindgut of the alimentary canals of insects.

i) Nephridia perform the function of excretion and osmoregulation in earthworms.

ii) Three types of nephridia are found in the earthworm based on their location, and they are

• Septal nephridia are present on both sides of the intersegmental septa of segment 15 to the last that opens into the intestine.
• Integumentary nephridia are attached to the lining of the body wall of segment 3 to the last that opens on the body surface.
• Pharyngeal nephridia are present as three paired tufts in the 4th, 5th and 6th segments.

The diagram of the reproductive organs of an earthworm is as follows:

The diagram of the alimentary canal of a cockroach is as follows:

a) Prostomium and peristomium

The differences are as follows:

b) Septal nephridium and pharyngeal nephridium

The cellular components of blood are Red blood cells (RBC), white blood cells (WBC) and platelets.

a) Chondrocytes are the cells of cartilage. Cartilage is present in the tip of the nose, outer ear joints, and between adjacent bones of the vertebral column, limbs and hands in adults. They are rounded, large and mature cells that are found occurring in clusters in the matrix of the cartilage.

b) An axon is a long slender projection of a neuron or nerve cell. They are present throughout the body. They emerge from the cyton and are responsible for conducting nerve impulses away from the cell body. They terminate in a group of branches known as terminal arborisations.

c) If the columnar or cuboidal cells bear cilia on their free surface, they are called the ciliated epithelium. They are present in the inner surface of hollow organs like bronchioles and fallopian tubes. It comprises fine vibratile cytoplasmic processes that are termed cilia, found on its free surface. This cilium is functional in trapping foreign substances and dust.

Epithelial tissues are found lining the body surface forming a protective surface. These cells are densely packed with a very little intercellular matrix.

Various types of epithelial tissues are

i) Simple epithelium:

It is a single layer of cells which functions as a lining for body cavities, ducts, and tubes.

Based on the structural modifications of the cells, Simple epithelial cells are further divided into 4 types.

• • Squamous epithelium

Simple epithelium is made of a single layer of a flattened cell having irregular boundaries. Since their cells represent tiles of a floor, they are also referred to as pavement epithelium. They are found in the walls of blood vessels and air sacs of the lungs. They are involved in excretion, protection, exchange of gases, secretion of coelomic fluid, etc.

• • Cuboidal epithelium

Cuboidal epithelium is made up of a single layer of cube-like cells. They are commonly found in ducts of glands and tubular parts of nephrons in kidneys, and their primary functions are secretion and absorption of gamete formation.

• • Columnar epithelium

The columnar epithelium is made of a single layer of tall and slender cells. They are found in the lining of the stomach and intestine and help in secretion and absorption. The nuclei of these cells are elongated and found at different positions. It aids in absorption and secretion.

• • Ciliated epithelium

If cuboidal or columnar epithelium has cilia, they are called ciliated epithelium. They are present in the inner surface of hollow organs like fallopian tubes and bronchioles. Their function is to move particles in a specific direction.

ii) Compound epithelium

The compound epithelium is a layer of two or more cells with a protective function, as it does in our skin. They are thick and strong compared to the simple epithelium, as they comprise two or more cell layers; they render protection. They cover the dry skin surface, the moist surface of the buccal cavity, and the inner lining of the ducts of pancreatic ducts and salivary ducts.

a. Simple epithelium and compound epithelium

b. Cardiac muscle and striated muscle

c. Dense regular and dense irregular connective tissues

d. Adipose and blood tissue

e. Simple gland and compound gland

1. The answer is neuron because it is not a connective tissue.
2. The answer is cartilage because it is not part of blood.
3. The answer is ligament because it is connective tissue, whereas the rest are glands.
4. The answer is antennae because the rest are the parts of a cockroach’s stomach.
5. The answer is Protenema because it is a thread-like chain of cells found in the life cycle of moss, whereas others are the parts of segments of a cockroach’s leg.