Lecture 8 (Male reproduction) Flashcards
Describe the male anatomy of the penis
- Internal
- resting inside the genital fold (prepucial sheath)
- evolved for hydrodynamic efficiency
Describe the tissue composition of cetacean penis and length
- NO BONE
- fibroelastic tissue (similar to cows/pigs)
- 2.5 to 3 m long and 25-30 cm in diameter
What shape does the penis make when retracted in cetaceans and does it lengthen during increased blood flow?
- S shape
- does not lengthen during increase blood flow
Which muscle helps stabililze the penis
- Retractor penis muscle
Where are the testes located?
- In the abdomen
- position varies depending on species
What is the Baculum and its purpose?
Which mammal has the largest and which has the smallest?
- ossified anterior portion of corpus cavernosum
- Penis bone
- prevent water damage to sperm
- Largest = walrus
- Smallest = otariids
Describe penile structure of Phocids
- Baculum - covered in thick glandular structure
- Scrotum - NONE
- Testes - external to abdomen muscles but covered by superficial muscles
Describe penile structure of Otariid
- Baculum - covered only by thin layer epithelium
- Scrotum - HAVE YES
- Testes - in some species withdrawn into inguinal position
How does a fractured baculum affect reproduction?
- failed reproductive abilites
What is the purpose of the scrotum?
- lower temp of testes
How are the testes cooled without a scrotum?
- Blood cooled by venous countercurrent
- arterial plexis blood cooled b/c heat transfer to venous return
- NOW cooler arterial blood keeps testes temp low
Where are the testes located in phocids?
- para-abdominal insulated by skin and 7-8 cm blubber
Where are the testes located in Otariids
- withdrawn into the inguinal area
- testes may descend into scrotum to avoid hyperthermia
Which species has the largest testes?
When do testes increase in weight?
Right whale
- Bigger than sperm whales
Testes weight increases during breeding season
How many times larger are odontocete testes compared to the average mammal?
- 7 to 25 times larger
What percentage of the body weight are the testes of Dusky dolphins? How does this compare to the human testes?
- 8%
- human testes = 0.08%
- 100x difference
How heavy are the Right Whale testes?
900 kgs (about 2% body weight)
Where are the testes of the sea otter and polar bear located?
- scrotum
Where are the testes of sirenians located?
- abdomen
In pinnipeds what happens to the testes during the seasons?
- changes in size and function
What is the purpose of the Vas Deferens?
- Delivers sperm to prostate
What is the purpose of the epididymus?
- Sperm stored
What is the purpose of the papiniform plexus?
- Supply testes with blood
What is the Mediastinum testes?
- support structure for vessels
What is the Tunica Albuginia?
- Connective tissue covering testes
What is the Parenchyma containing seminiferous tubules?
- Contains sertoli cells that make sperm
Where is the prostate located and what is its purpose?
- Surrounds urethra just after bladder
- Produces seminal fluid for sperm viability and motility
- Musculoglandular organ
How does the prostate gland compare between pinniped species?
- no, pinniped prostates are similar in physiology across all seals
How does the prostate gland compare between cetacean species?
- variable but little is known
- Beluga only rudimentary
- largest in dolphin
How does the prostate gland compare between sirenian species?
- manatee very muscular
- dugong no discrete prostate
How does the prostate gland present in polar bears?
- small prostate
Where does conception occur?
- in the womb
Why do dolphins mate quickly?
- Avoid predators (sharks and whales)
- Salt water can kill sperm
- Female vagina locks around the penis to create a water tight seal
During week 9 of dolphin development what happens?
- nostrils merge and form blowhole
During weeks 11-12 of dolphin development what happens?
- sexual development
What happens in week 12 of dolphin development?
- Fetus must swim in womb to maintain proper body temp
During weeks 24 -28 during dolphin development, what happens?
- Tail formed
- eyes open and close
During week 36 what happens in dolphin development?
- Whiskers on both sides of rostrum
- Skin now dolphin color
- Insulation blubber layer started to form
During week 52 what happens in dolphin development?
- Birth
- Weighs around 30 pounds
- Born caudal fin first
- Fins folded against body to prevent injury to mother
- Mother may nurse for 2 years
- Whiskers eventually fall out due to water pressure
