31.2
睾丸：大体解剖学
睾丸，也称为睾丸，是男性生殖腺。它们位于阴囊内，阴囊是位于阴茎下方的囊状结构。阴囊的主要作用是调节睾丸的温度，这对精子的产生至关重要。
每个睾丸都被一层称为白膜的致密结缔组织层所包围，提供结构支撑和保护。这层白膜被一层称为鞘膜的外浆膜覆盖，有助于减少睾丸与周围结构之间的摩擦。
阴囊由一层薄薄的皮肤、…
成对的睾丸是雄性生殖腺。
每个睾丸重10至15克，长约5厘米，宽3厘米，厚2.5厘米。
白膜是一层致密的结缔组织，为睾丸提供结构支持。
其外部由鞘膜（tunica vaginalis）覆盖，鞘膜是一种浆膜，衬于阴囊内，将睾丸悬吊于会阴下方。
阴囊具有薄层的皮肤、浅筋膜和肌肉。
阴囊中隔为每个睾丸形成独立的腔室，其由一层皮下筋膜和称为肉膜的平滑肌构成。
该肌肉还沿阴囊皮下层走行，可引起阴囊表面皱缩，从而减少热量散失。
此外，提睾肌的骨骼肌纤维会收缩，使睾丸在性兴奋或外界温度降低时更靠近身体。
这些阴囊肌肉使睾丸温度比身体其他部位低约2至3华氏度，这是精子发育的理想温度。
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Q1: What are the testes and where are they located?
The testes, also called testicles, are the male gonads that produce sperm and hormones essential for reproduction. Each testis weighs 10 to 15 grams and measures approximately 5 cm long, 3 cm wide, and 2.5 cm thick. They are housed within the scrotum, a sac-like structure located beneath the penis that provides protection and temperature regulation.
Q2: What is the tunica albuginea and what role does it play?
The tunica albuginea is a dense connective tissue layer that surrounds each testis, providing structural support and protection. It is externally covered by the tunica vaginalis, a serous membrane that lines the scrotum and helps reduce friction between the testes and surrounding structures, allowing them to move freely.
Q3: How does the scrotum maintain optimal testicular temperature?
The scrotum maintains testicular temperature 2 to 3 degrees Fahrenheit lower than the rest of the body through two mechanisms. The dartos muscle wrinkles the scrotal skin to reduce heat loss, while the cremaster muscles, made of skeletal muscle fibers, contract during cold temperatures or sexual arousal to pull the testes closer to the body, protecting them from excessive cooling.
Q4: What is the scrotal septum and how is the scrotum divided?
The scrotal septum is a fibrous partition composed of subcutaneous fascia and smooth muscle that divides the scrotum into two separate chambers, each housing one testis. This structural division prevents the testes from moving freely between sides and helps maintain independent temperature regulation for each gonad.
Q5: What are the layers of the scrotal wall?
The scrotal wall consists of a thin layer of skin, superficial fascia, and muscle layers that provide physical protection to the testes. The dartos muscle runs along the subcutaneous layer and causes wrinkling of the scrotal surface, while the cremaster muscles extend from the abdominal wall to assist in thermoregulation and support.
Q6: Why is temperature regulation critical for testicular function?
Temperature regulation is essential because the testes require a cooler environment than the rest of the body for optimal sperm development and production. The scrotum's thermoregulatory mechanisms maintain this ideal temperature differential, ensuring the testes function effectively and support male fertility and reproductive capacity.
Q7: How do the dartos and cremaster muscles work together?
The dartos muscle, composed of smooth muscle in the subcutaneous layer, wrinkles the scrotal skin to reduce heat loss passively. The cremaster muscles, made of skeletal muscle fibers, actively contract in response to cold or sexual arousal, pulling the testes upward toward the body. Together, these muscles provide dual thermoregulatory control to maintain optimal testicular conditions.