Week 11

Question 1

What cell types are within the testes?

Answer 1

1. Spermatogonia: derived from primordial germ cells
2. Sertoli cells: derived from intermediate mesoderm
3. Peritubular myoid cells: smooth muscle cells that surround each seminiferous tubule
4. Immune cells: present in interstitial tissue
5. Germinal epithelium:

Question 2

What are some important functions of Sertoli cells?

Answer 2

1. Express SRY
2. Produce AMH during development
3. Secretes inhibin to control FSH release
4. Supports developing sperm cells: blood-testis barrier. provides nutrients and synthesised ABP
5. Maintains spermatogonial stem cells (which are outside the blood-testis barrier)

Question 3

Describe the development of PGCs in the embryo:

Answer 3

1. Specification:
   - Around 6 cells express Blimp1
2. Commitment:
   - After proliferation a subset of Blimp1 positive cells also express Stella and commit to the germline
3. Migration:
   - Passive and active migration to the gonads
4. Colonisation:
   - PCGs colonise the gonads and undergo sex determination

Question 4

Describe the key points of environmental adaptation:

Answer 4

1. Environment (pressure)
2. Phenotype
3. Genotype
4. Adaptation (solutions)
5. Morphology outward phenotypic expression that is shaped by a process of adaptation, selection and random genetic drift

Question 5

Where did humans evolve?

Answer 5

• Humans evolved largely in Africa in tropical/subtropical climates
• Occurred around 7 million years ago in East Africa (rift valley)
• Humans have 1.4% different genes to chimpanzees , this accounts for 1 genetic change per 10,000 years (700 genes in 7 million years)

Question 6

What anatomical adaptations do humans have since out last common ancestor chimpanzees?

Answer 6

1. Encephalisation:
   - Large increase in brain size compared to body size
   - Occurred fairly late in human evolution
2. Masticatory Evolution (dental reduction, enamel)
3. Vocal tract modification (descended larynx- we cannot breathe and drink at the same time beyond infancy)
4. Integumentary changes
5. Alteration to pattern of manipulation (precision over power)
6. Habitual bipedalism (first major adaptation of hominins)

Question 7

How are we anatomically different to chimpanzees to allow us to be bipedal?

Answer 7

1. Reorganisation of pelvis:
   - Humans have a short pelvis and wide sacrum
   - Humans have a reinforced pelvic floor
2. Changes to foot:
   - Humans have a robust first digit (hallux)
3. Changes to hindlimbs:
   - Humans have much longer hindlimbs
4. Changes to vertebral column:
   - Humans have 2 curves of their spine (secondary curvatures)

Question 8

Problems due to the adaptation of bipedalism:

Answer 8

1. Issues with spinal cord:
   - Shifting body mass puts incredible pressure on intervertebral discs
   - This can cause the development of nucleus pulpsosis
2. Inguinal hernias:
   - Due to us having an anterior abdominal wall
   - The pushing down of the organs exposes a weak spot
3. The obstetric dilemma:
   - The pelvis has been shaped to accommodate bipedality
   - Increases in brain size have also occurred
   - There must be a comprimise between birthing large headed infants and having a pelvis optimal of bipedality