Internal Structure of Flowering Plants and Mammals

1. Internal Structure of a Flowering Plant

The internal anatomy of a flowering plant consists of tissues organized into three main organs: roots, stems, and leaves. These tissues are specialized for protection, support, and transport.

A. The Root (Transverse Section)

In a typical dicot root, the tissues from the outside inward are:

• Epidermis (Piliferous layer): Single layer of cells with root hairs for water and mineral absorption.
• Cortex: Large area of parenchyma cells for storage and transport.
• Endodermis: The innermost layer of the cortex, regulating water flow into the vascular cylinder.
• Pericycle: Layer inside the endodermis where lateral roots originate.
• Vascular Bundles: Xylem (usually star-shaped in the center) and Phloem (located between the arms of the xylem).

B. The Stem (Transverse Section)

The stem provides support and transports fluids.

• Dicot Stem: Vascular bundles are arranged in a ring around a central pith.
• Monocot Stem: Vascular bundles are scattered throughout the ground tissue.
• Tissues: Epidermis (protection), Cortex (support/storage), Xylem (water transport), and Phloem (food transport).

C. The Leaf (Transverse Section)

• Cuticle: Waxy layer to prevent water loss.
• Epidermis: Upper and lower layers; contains stomata for gas exchange.
• Mesophyll: Divided into Palisade mesophyll (tightly packed, high chloroplast count for photosynthesis) and Spongy mesophyll (loose cells for gas exchange).
• Vascular bundles: Found in the veins; contain xylem and phloem.

D. Supporting Tissues in Plants

Plants require mechanical support to stay upright and withstand environmental stress:

• Collenchyma: Living cells with thickened cellulose walls at corners. Provides flexibility and support in young stems.
• Sclerenchyma: Dead cells with heavily lignified walls. Found in mature parts of the plant (e.g., fibers).
• Xylem: Provides structural support due to lignified tracheids and vessels.
• Phloem Fibres: Provide additional mechanical strength to the vascular system.

2. Internal Structure of a Mammal

Mammalian internal organs are organized within two main cavities: the Thoracic cavity (chest) and the Abdominal cavity, separated by the Diaphragm.

A. Digestive Organs

• Stomach: Located on the left side of the upper abdomen; J-shaped organ for protein digestion.
• Liver: Large, dark-red organ located on the right side; produces bile.
• Small Intestine: Long coiled tube for digestion and absorption.
• Pancreas: Located behind the stomach; secretes digestive enzymes and insulin.

B. Excretory Organs

• Kidneys: Bean-shaped organs located against the back wall of the upper abdomen.
• Ureters: Tubes carrying urine from kidneys to the bladder.
• Urinary Bladder: Sac-like structure in the pelvic cavity for storing urine.

C. Reproductive Organs

• Male: Testes (located in the scrotum), Vas deferens, and Prostate gland.
• Female: Ovaries (produce eggs), Fallopian tubes (site of fertilization), and Uterus (site of embryo development).