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<p>Lymphoid precursors migrate into the developing bursa during the first few weeks of embryo development. The bursa continues to grow through development and in chickens the bursa reaches its maximum size by six weeks. After this it slowly regresses (involutes) until only a small remnant is present in the adult.</p>
<p>Lymphoid precursors migrate into the developing bursa during the first few weeks of embryo development. The bursa continues to grow through development and in chickens the bursa reaches its maximum size by six weeks. After this it slowly regresses (involutes) until only a small remnant is present in the adult.</p>
==Structure==
==Structure==
<p>The bursa is a round out-pouching of the [[The Avian Vent and Cloaca - Anatomy & Physiology|cloaca]]. It is found on the caudodorsal surface of the [[The Avian Vent and Cloaca - Anatomy & Physiology|cloaca]] (in the proctodeum) cranial to the dorsal proctodeal gland. The bursa consists of a number of lymphoid lobules and crypt-like folds surrounding a lumen, which enclosed in a thin layer of stratified squamous epithelium. The lumen opens into the proctodeum.</p>
<p>The bursa is a round out-pouching of the [[The Avian Vent and Cloaca - Anatomy & Physiology|cloaca]]. It is found on the caudodorsal surface of the [[The Avian Vent and Cloaca - Anatomy & Physiology|cloaca]] (in the proctodeum) cranial to the dorsal proctodeal gland. The bursa consists of a number of lymphoid lobules and crypt-like folds surrounding a lumen, which is enclosed in a thin layer of stratified squamous epithelium. The lumen opens into the proctodeum.</p>
<p>Like the [[Thymus - Anatomy & Physiology|thymus]] the lobules have a cortex and medulla and the [[Lymphocytes - WikiBlood|lymphocytes]] are supported by epithelial cells. [[Lymphocytes - Anatomy & Physiology#B cells|B lymphocytes]] developing from the lymphoid precursors gather in the cortex, hence the cortex stains stronger than the medulla.</p>
<p>Like the [[Thymus - Anatomy & Physiology|thymus]] the lobules have a cortex and medulla and the [[Lymphocytes - WikiBlood|lymphocytes]] are supported by epithelial cells. [[Lymphocytes - Anatomy & Physiology#B cells|B lymphocytes]] developing from the lymphoid precursors gather in the cortex, hence the cortex stains stronger than the medulla.</p>
===Histology===
===Histology===