Week 1 Gametes OBA Lecture PDF

Male gamete: Spermatozoon (sperm, sperm cells) A mature spermatozoon  Objectives You should be able to describe a mature male gamete (spermatozoon) You should be able to understand some clinical significance of the sperm A mature spermatozoon  Anatomic parts of sperm...

Male gamete: Spermatozoon (sperm, sperm cells) A mature spermatozoon  Objectives You should be able to describe a mature male gamete (spermatozoon) You should be able to understand some clinical significance of the sperm A mature spermatozoon  Anatomic parts of spermatozoon Head Neck Middle piece tail  Characteristics of the sperm Microscopic Elongated, like a tadpole (about 60 µm) Highly motile (about 3 mm/min) Highly differentiated Haploid – (23 chromosomes) Viable for average of 48 hours in the female tract  Head of a spermatozoon The head of a spermatozoon is the anterior ovoid or piriform end. About 4 µm long and 3 µm wide at its widest part Contains a densely-parked nucleus, and the acrosomal cap Acrosomal cap overlies anterior ⅔ of the nucleus  Head of spermatozoon The head of a spermatozoon is the anterior ovoid or piriform end. About 4 µm long and 3 µm wide at its widest part Contains a densely- parked nucleus, and the acrosomal cap Acrosomal cap overlies anterior ⅔ of the nucleus  Contents of acrosome These include (some lysosomal) enzymes: – Acrosin (a proteinase) – Hyaluronidase (hydrolysis of hyaluronic acid) – Neuraminidase (sialidase, a glycohydrolase; hydrolysis of glycosides) – Arylsulphatase (hydrolysis of sulphate moiety of glycoproteins) The acrosomal cap is derived from the Golgi apparatus. external to nucleus and acrosome is the cell membrane No cytoplasm intervenes between them  Sperm nucleus Nature: highly condensed/compact (nuclear protein in sperm is protamine) Location: head of sperm (behind acrosome) Forms male pronucleus at fertilization Is haploid (has 23 chromosomes)  Neck of the sperm Is a small constriction Position: just caudal to the head Length: about 0.3 µm Contains centrioles proximally and basal body distally Also contains a little amount of cytoplasm  Middle piece of sperm Location: just distal to neck Length: 7 µm long (cylindrical portion) Structure: made of the central axoneme, and spiral sheath of mitochondria  Middle piece of sperm Axoneme: consists of a central pair of microtubules surrounded by nine pairs of microtubules. Dynein and radial spokes (protein complexes) are associated with these microtubules mitochondrial sheath surrounds axoneme. Mitochondria are arranged in a helical pattern around axoneme Mitochondria generate ATP for sperm motility  Tail of spermatozoon caudal part of a spermatozoon Long tapering process : is about 40 µm long & 0.5 µm wide resembles a flagellum. Its core is has the axoneme (bundle of microtubules) plasma membrane envelops the tail externally repeated movement of the tail produces sperm motility (of 3 mm/minute) THE OVUM MORPHOLOGY HUMAN OVUM (200 µM)  CHARACTERISTICS Rounded Large (200 µm; size of pin head) Immotile Viable for about 24 hours post-ovulation Rich in nutritive yolk – Lecithin (lipid) – Isolecithal  The gametes 1 =nucleolus 2 =nucleus 3 =zona pellucida 4 =head 5 =acrosome 6 =centriole 7 =mitochondrion 8 =tail 9 =middle piece 10 =neck 11 =corona radiata 12 =cytoplasm OVUM SPERM  PARTS OF THE OVUM Nucleus (germinal vesicle) – haploid (23 chromosomes) Nucleolus (germinal spot) Cytoplasm (vitellus, yolk, ooplasm) – Formative yolk (= normal cytoplasm; has organelles) – Nutritive yolk (=deutoplasm; has lecithin; isolecithal) Cortical granules – Contain enzymes Cell membrane Zona pellucida – of glycoprotein Miss. Egg , I miss you very much! Mr. Sperm , I miss you very much too ! Study questions 1. Give a brief definition of embryology 2. List and define specific stages in human embryogenesis 3. Draw, label and describe a mature human spermatozoon 4. Draw, label and describe a mature human ovum 5. Write a short note on the clinical correlates of the human gametes