5A.Human reproductive system

• The testes in man are located in a pouch outside the abdomen called scrotal sacs (scrotum)
• Each testis is enclosed in a fibrous envelope called the tunica albuginea
• The testis is covered by an outer peritoneal layer called tunica vaginalis
• The canals that connect the cavities of the scrotal sac and abdominal cavity are the inguinal canal
• The structures that keep the testes in their position are the gubernaculum, a fibrous cord that connects the testis to the bottom of the scrotal sac
• Sertoli cells of the seminiferous tubules are nourishing cells that nourish the spermatozoa and produce a hormone called inhibin, which stops the production of FSH. They are present along with sperm mother cells
• Leydig cells are interstitial cells present between columns of seminiferous tubules. They secrete androgens, with Testosterone being important
• The copulatory organ of man is the penis
• It has three columns of tissues:

  • The two upper (dorsal) columns are corpora cavernosa
  • The single ventral column is corpus spongiosum
• Spermiogenesis is the process in which spermatids transform into spermatozoa
• Spermiation is the process in which spermatozoa (sperm heads) are released from seminiferous tubules
• After ovulation, the empty follicle is filled with a yellow mass of glandular cells called corpus luteum
• It secretes progesterone which maintains pregnancy
• The gestation period is the period of development of an embryo inside the uterus, from inception (fertilization) to delivery (parturition)
• Human pregnancy (gestation) is about 38 weeks from fertilization or 40 weeks from the last menstrual cycle
• Implantation:

  • Occurs early in human pregnancy (after 6th day of fertilisation)
  • Human embryo (blastocysts) adheres to the wall of the uterus
• Epiblast:

  • After implantation, the outer layer of cells of germinal disc of blastocyst forms the epiblast
  • Future ectoderm
• Hypoblast:

  • After implantation, the inner cell layer facing the blastocyst cavity forms the Hypoblast
  • Future extraembryonic endoderm
• Two major functions of testis:

  • Produces sperms and male hormones (Testosterone) called androgens
• Two major functions of ovary:

  • Produces ova
  • Produces female hormones estrogen and progesterone
• Labelled diagram of a sperm:

  • Head
  • Plasma membrane
  • Acrosome
  • Nucleus containing chromosomal material
  • Neck
  • Middle piece
  • Mitochondria (energy source for swimming)
  • Tail
• Major components of the seminal fluid:

  • Fructose
  • Proteins
  • Citric acid
  • Inorganic phosphorous
  • Potassium
  • Prostaglandins
  • Due to secretion of Seminal vesicles, prostate glands, cowpers glands
• Menstrual cycle:

  • The reproductive cycle in the human female primates
  • Cyclic changes occur in the uterus every 28/29 days
  • Regulated mainly by four hormones:
  • Follicle stimulating hormone (FSH)
  • Luteinizing hormone (LH) from the pituitary
  • Estrogen
  • Progesterone from the ovary
• Parturition:

  • The process of delivery of childbirth
  • Oxytocin induces parturition
• For the formation of six puppies, six eggs (ova) are released, unless there are no identical twins
• Neurulation:

  • The process of formation of the neural tube from the neural plate in the embryo, as part of organogenesis
• Capacitation of sperm:

  • Refers to the physiological changes that spermatozoa undergo to penetrate and fertilize an egg
• Compaction in human development:

  • The process of firm binding between cells at the morula stage
  • Blastomeres change shape and align tightly against each other to form the compact morula
• Involution vs. Ingression in human development:

  • Involution: The inward growth and curling inward of a group of cells in the formation of a gastrula from a blastula
  • Ingression: The inward migration of future endodermal cells from the epiblast during gastrulation
• Four extra embryonic membranes:

  • Amnion
  • Allantois
  • Yolk sac
  • Chorion