`star` Digestive System
`star` Circulatory System
`star` Respiratory System


● The body wall of the `color{violet}("earthworm")` is covered externally by a thin `color{brown}("non-cellular cuticle")` below which is the epidermis, two muscle layers `color{violet}("(circular and longitudinal)")` and an innermost coelomic epithelium.

● The `color{brown}("epidermis")` is made up of a `color{violet}("single layer of columnar epithelial cells")` which contain secretory gland cells.

● The `color{brown}("alimentary canal")` is a `color{violet}("straight tube")` and runs between first to last `color{violet}("segment of the body.")`

● A `color{violet}("terminal mouth")` opens into the `color{violet}("buccal cavity")` (1-3 segments) which leads into `color{brown}("muscular pharynx")`.

● A small narrow tube, `color{brown}("oesophagus")` (5-7 segments), continues into a `color{brown}("muscular gizzard")` (8-9 segments).

● It helps in `color{violet}("grinding")` the `color{violet}("soil particles")` and decaying leaves, etc.

● The `color{brown}("stomach")` extends from 9-14 segments.

● The food of the `color{violet}("earthworm")` is decaying leaves and `color{violet}("organic matter")` mixed with soil.

● `color{brown}("Calciferous glands,")` present in the `color{violet}("stomach, neutralise")` the humic acid present in humus.

● Intestine starts from the 15th segment onwards and continues till the last segment.

● A pair of short and conical `color{brown}("intestinal caecae")` project from the `color{violet}("intestine")` on the 26th segment.

● The characteristic feature of the `color{violet}("intestine")` between 26-35 segments is the presence of internal median fold of dorsal wall called `color{brown}("typhlosole.")`

● This increases the `color{violet}("effective area")` of absorption in the `color{violet}("intestine.")`

● The `color{violet}("alimentary canal")` opens to the exterior by a small rounded aperture called `color{brown}("anus")`.

● The ingested `color{violet}("organic rich soil")` passes through the digestive tract where digestive `color{violet}("enzymes breakdown
complex food")` into smaller `color{violet}("absorbable units.")`

● These `color{violet}("simpler molecules")` are absorbed through `color{violet}("intestinal membranes")` and are utilised.


● `color{violet}("𝘗𝘩𝘦𝘳𝘦𝘵𝘪𝘮𝘢")` exhibits a `color{brown}("closed type of blood")` vascular system, consisting of `color{violet}("blood vessels, capillaries and heart.")`

● Due to `color{violet}("closed circulatory")` system, `color{violet}("blood")` is confined to the heart and blood vessels.

● Contractions keep `color{violet}("blood circulating")` in one direction.

● Smaller `color{violet}("blood vessels supply")` the gut, nerve cord, and the body wall.

● `color{brown}("Blood glands")` are present on the 4th, 5th and 6th segments.

● They produce `color{brown}("blood cells")` and `color{brown}("haemoglobin")` which is dissolved in blood plasma.

● `color{violet}("Blood cells")` are `color{violet}("phagocytic")` in nature.


● Earthworms `color{brown}("lack specialised")` breathing devices.

● Respiratory exchange occurs through `color{brown}("moist body surface")` into their `color{violet}("blood stream")`