Questions and Answers
What is the cloaca?
It is the expanded terminal end of the hindgut, before its division into rectum, bladder, and genital primordia.
What divides the cloaca into dorsal and ventral parts?
Mesenchyme - urorectal septum
Where does the urorectal septum develop?
In the angle between the allantosis and hindgut during week 3.
How does the urorectal septum grow?
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With which germ layer does the urogenital septum fuse?
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The three parts of the cloaca are the rectum, cranial part of the anal canal, and the ______.
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What are the three parts of the urogenital sinus?
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What composes the lower part of the rectum?
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What composes the upper 2/3 part of the rectum?
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Study Notes
Cloaca Overview
- The cloaca is the terminal end of the hindgut, before it divides into the rectum, bladder, and genital primordia.
- It has an endoderm-lined structure, interacting with surface ectoderm at the cloacal membrane.
- The cloacal membrane consists of the endoderm of the cloaca and ectoderm of the anal pits.
Division of Cloaca
- The urorectal septum, composed of mesenchyme, divides the cloaca into dorsal and ventral parts.
Urorectal Septum Development
- The urorectal septum forms in the angle between the allantois and hindgut during week 3 of embryonic development.
- It grows towards the cloacal membrane and fuses by week 6, creating a partition that separates the cloaca into three distinct parts.
Urogenital Septum Formation
- The urogenital septum fuses with the ectoderm germ layer.
Parts of the Cloaca
- The cloaca divides into three components:
- Rectum
- Cranial part of anal canal
- Urogenital sinus
Urogenital Sinus Structure
- The urogenital sinus consists of three parts:
- Vesical part: forms the bladder
- Pelvic part: comprises the urethra and neck of the bladder
- Phallic part: develops into the primordium of the penis or clitoris
Rectum Composition
- The lower part of the rectum is lined with ectoderm up to the pectinate line, featuring stratified squamous cells.
- The upper two-thirds of the rectum is lined by endoderm, containing columnar cells.
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Description
Explore the intricate development of the cloaca, sinus urogenitalis, and urinary bladder through this educational quiz. Understand the anatomical significance and the biological processes involved in these structures. Ideal for students of developmental biology and anatomy.
