Gizzard - Anatomy & Physiology

BACK TO THE AVIAN DIGESTIVE TRACT - ANATOMY & PHYSIOLOGY

Introduction

The gizzard is also referred to as the muscular stomach. It is connected by the isthmus to the proventriculus and to the duodenum.

Structure and Function

Gizzard Anatomy - RVC 2008

• Mechanical reduction of tougher material through powerful muscular development

• Cranial to the liver and spleen (contacts the liver)

• Contacts the sternum and lower left abdominal wall

• Dorsally the abdominal air sacs separate it from the intestines and gonads

• Duodenum and pancreas lies in its caudal right surface

• More caudal than the proventriculus

• Roughly on the midline of the bird

• Lens shaped

• Interior elongated by cranial and caudal blind sacs

• Cranial blind sac contacts proventriculus

• Pylorus on right surface next to cranial blind sac

• Two thick masses of muscle that insert on tendonous surfaces

• In seed eating birds grit is digested to increase grinding down of food particles

• Surface covered by glistening tendonous layer

• The cranial and caudal extremities are formed by powerful red muscular tissue

• A circular aponeurosis is present connecting the cranial end of the gizzard to the isthmus and the caudal end to the duodenum

Histology

• Thin, but tough mucous membrane

• Pale, thin lining raised into ridges

• 3 layers of lamina muscularis

• Cuboidal epithelium

• Tubular glands

• Cuticle of koilin a carbohydrate complex is present due to the solidifying of the glandular secretion. It is replenished as it is worn down.

• Thick keratin layer to protect muscle

Species Diffences

• No gizzard in falconiformes (raptors etc.)

• No gizzard in stringiformes (owls etc.)

• No gizzard in gulls

Other Information

• Grit should be provided in seed eating birds diet. It is radiodense and marks out where the gizzard is located on radiographs.