Important Diagrams: Structural Organisation in Animals | Biology Class 11 - NEET PDF Download

Animal Tissues

Animal tissue refers to the group of cells in an animal that perform a specific function. These tissues are categorized into four main types: epithelial, connective, muscle, and nervous tissues. Each type has distinct structures and functions that contribute to the overall health and operation of the animal body.

Let's study them in Detail through diagrams one by one.

Epithelial Tissue 

Epithelial tissue is a type of tissue that forms the outer layer of the body's surfaces and lines the internal organs and cavities. It serves as a protective barrier against mechanical, chemical, and biological stress. Its cells are closely packed and arranged in one or more layers, and it is involved in functions like absorption, secretion, and sensory processes.

1. Types of Simple Epithelium

• Squamous Epithelium: A single layer of thin, flat cells with irregular boundaries, found in blood vessel walls and lung air sacs, primarily for facilitating diffusion.
• Cuboidal Epithelium: Composed of cube-shaped cells, located in gland ducts and kidney nephrons, specialized in secretion and absorption.
• Columnar Epithelium: Features a single layer of tall, slender cells with nuclei at the base and often microvilli on the surface, key for secretion and absorption in the stomach and intestines.
• Ciliated Epithelium: Columnar or cuboidal cells equipped with cilia to move substances across their surface, commonly lining the bronchioles and fallopian tubes.

Simple epithelium: (a) Squamous (b) Cuboidal (c) Columnar (d) Columnar cells bearing cilia

2. Types of Glandular Epithelium

Glandular epithelium, specialized for secretion, includes unicellular types like goblet cells and multicellular types like salivary glands, classified into exocrine (secreting products like mucus and enzymes via ducts) and endocrine glands (releasing hormones directly into surrounding fluids).

Glandular epithelium : (a) Unicellular (b) Multicellular

3. Compound Epithelium

Connective Tissue - Adipose, Areolar, Dense, Special.

1. Areolar Connective Tissue

Loose connective tissue, featuring cells and fibers in a semi-fluid matrix like areolar tissue beneath the skin, supports epithelium and contains fibroblasts, macrophages, and mast cells.

Areolar Connective Tissue

2. Adipose Tissue

Adipose Tissue

3. Dense Connective Tissue

Dense connective tissues, where fibers and fibroblasts are tightly packed, exhibit either a regular arrangement forming structures like tendons and ligaments, or an irregular orientation found in the skin.

Dense Connective Tissue: (a) Regular (b) Irregular

4. Special Connective Tissues

• Cartilage, with its solid and pliable matrix, houses chondrocytes in small cavities and is mainly found in areas like the nose, outer ear, and joints, while in adults, much of it transitions to bone. 
• Bones, composed of calcium salts and collagen, provide structural support, protect organs, aid movement through interaction with muscles, and contain marrow for blood cell production.

Special Connective Tissue (a) Cartilage (b) Bone

Blood, a fluid connective tissue with plasma, RBCs, WBCs, and platelets, circulates to transport substances throughout the body.
Special Connective Tissue (c) Blood

Types of Muscle Tissue

• Skeletal muscle tissue, like in the biceps, consists of striated fibers aligned parallel and encased in connective tissue, attaching directly to bones and enabling voluntary movement. 
• Smooth muscle, found in internal organs like blood vessels and the digestive tract, features non-striated, fusiform fibers that operate involuntarily, controlled automatically by the body. 
• Cardiac muscle, exclusive to the heart, has intercalated discs among fused cells allowing synchronized contractions essential for pumping blood.

(a) Skeletal muscle (b) Smooth muscle (c) Cardiac muscle

Nervous Tissue

Neurons, the unit of neural system are excitable cells. The neuroglial cell which constitute the rest of the neural system protect and support neurons.

Structure of Neuron

Morphology and Anatomy of Cockroach

External Features of Cockroach

Adult Periplaneta americana cockroaches are 34-53 mm long, with males having wings that extend beyond their abdomen, and possess a segmented body divided into head, thorax, and abdomen, all protected by a hard, brown chitinous exoskeleton with sclerites linked by a flexible arthrodial membrane.

Morphology of Cockroach

Head region of cockroach

The cockroach's head is triangular, positioned anteriorly at right angles to the body, highly mobile due to a flexible neck, equipped with compound eyes, thread-like sensory antennae, and mouthparts for biting and chewing, including a labrum, mandibles, maxillae, labium, and a tongue-like hypopharynx.

Alimentary Canal of Cockroach

Alimentary Canal of Cockroach

Open Circulatory System of Cockroach

Circulatory System of Cockroach

Reproductive System of Cockroach

• Males have a pair of testes in the 4th-6th abdominal segments, connected by vas deferens to the ejaculatory duct and a mushroom-shaped gland in the 6th-7th segments acting as an accessory gland. 
• Females have two large ovaries in the 2nd-6th segments, each with ovarian tubules leading to a median oviduct that opens into the genital chamber, complemented by spermatheca for sperm storage in the 6th segment. The fertilized eggs are encased in oothecae, which are deposited in moist areas.

Reproductive System of Cockroach : (a) male (b) female

Morphology and Anatomy of Frog

External Features of Frog

• Frog skin is smooth and moist due to mucus, olive green on the dorsal side with spots, and pale yellow on the ventral.
• Frogs absorb water through their skin and feature a body divided into head and trunk, with webbed digits for swimming and distinct sexual dimorphism visible in vocal sacs and copulatory pads in males.

External Features of Frog

Digestive System of Frog

Digestive System of Frog

Male Reproductive System of Frog

Male reproductive organs consist of a pair of yellowish ovoid testes, which are found adhered to the upper part of kidneys by a double fold of peritoneum called mesorchium. Vasa efferentia are 10-12 in number that arise from testes. They enter the kidneys on their side and open into Bidder’s canal.

Male Reproductive System of Frog

Female Reproductive System of Frog

Female frogs have a pair of ovaries located near the kidneys, with oviducts extending from the ovaries to open separately into the cloaca; external fertilization occurs in water, with females capable of laying 2500 to 3000 ova that develop through a tadpole larval stage into adulthood.

Female Reproductive System of Frog

Diagram Based Previous Year Questions NEET

Q1: Match List I with List II related to digestive system of cockroach. (NEET 2024)

Choose the correct answer from the options given below:
(a) A-IV, B-II, C-III, D-I
(b) A-I, B-II, C-III, D-IV
(c) A-IV, B-III, C-II, D-I
(d) A-III, B-II, C-IV, D-I

Ans: (a)

The digestive system of a cockroach consists of several specialized structures that perform specific functions:
Crop is a part of the alimentary canal where food is stored temporarily. This aligns with the description for List I "A. The structures used for storing of food". Thus, A corresponds to IV (Crop).
Gastric Caeca are blind tubules located at the junction of the foregut and the midgut in insects. These tubules secrete enzymes and provide an increased surface area for digestion and absorption. This fits the description for List I "B. Ring of 6-8 blind tubules at junction of foregut and midgut". Hence, B corresponds to II (Gastric Caeca).
Malpighian tubules are thin filamentous structures present at the junction of the midgut and hindgut. They are primarily involved in excretion and osmoregulation. They match the description for List I "C. Ring of 100-150 yellow coloured thin filaments at junction of midgut and hindgut". Thus, C corresponds to III (Malpighian tubules).
Gizzard, also known as the proventriculus, is equipped with hard chitinous plates that grind the food mechanically. This description fits List I "D. The structures used for grinding the food". Therefore, D corresponds to I (Gizzard).
By collaborating all this information, the correct answer is: Option A: A-IV, B-II, C-III, D-I

Q2: Which of the following is characteristic feature of cockroach regarding sexual dimorphism?(NEET 2023)
(a) Dark brown body colour and anal cerci
(b) Presence of anal styles
(c) Presence of sclerites
(d) Presence of anal cerci

Ans: (b)

• Option (b) is the correct answer because anal styles are present in male cockroaches and absent in female cockroaches.
• Option (a), (c) and (d) are not the correct answers because sclerites, anal cerci and dark brown body colour are common features of both male and female cockroaches.
  

Q3: Tegmina in cockroach, arises from: (NEET 2022 Phase 1)
(a) Metathorax 
(b) Mesothorax 
(c) Prothorax and Mesothorax 
(d) Prothorax

Ans:(b)

• Option (b) is the correct answer because tegmina or forewings (the first pair of wings) in cockroach arises from mesothorax.
• Options (a), (c) and (d) are incorrect because no wing arises from prothorax and hindwings arise from metathorax.