First Week of Human Development

Last updated: November 10, 2024

Major differences between oogenesis and gametogenesis

	Oogenesis	Spermatogenesis
Definition	Production of oocytes from oogonia	Production of spermatozoa from spermatogonia
Location of stages	2 stages. Meiosis I in the Ova and Meiosis II completes in the fallopian tube	Meiosis I and Meiosis II all occur in the testes
Continuity	Early oogenesis occurs during the fetal period. The remaining stages occur from puberty to menopause	A continuous process from puberty to death
Length of growth phase	Prolonged	Shortened
Polar body	Produced after Meiosis I	No polar bodies are formed
Motility of the gametes	Produces non-motile gametes	Produces motile gametes

Distinguish between mitosis and meiosis

	Mitosis	Meiosis
Number of divisions	One	Two
Independent assortment	Does not occur	Occurs in metaphase I
Synapsis	Does not occur	Occurs forming bivalents
Crossing over	Does not occur	Occurs in prophase I
Outcome	Two daughter cells	Four daughter cells
Cell ploidy	Diploid cells	Haploid cells
Utility	Division of body cells	Formation of gametes
Genetics of daughter cells	Identical to parent cells	Variation exists

Outline the stages/ phases of mitosis and state key events of each stage

Prophase: Chromosomes condense, Spindle fibers form
Metaphase: Chromosomes align at the equatorial or metaphase plate
Anaphase: Sister chromatids are cleaved to form 2 identical daughter chromosomes
Telophase: The nuclear envelope forms around the chromosomes
Cytokinesis: The cell divides into 2 halves

Name the hormones involved in the regulation of the uterine and ovarian cycles and state their respective roles

Gonadotropin-releasing hormone (GnRH): Released from the hypothalamus to stimulate the anterior pituitary to produce FSH and LH
Follicle Stimulating Hormone (FSH): Stimulates the granulosa cells and recruits a group of maturing follicles in the ovary. Follicular cells produce estradiol and Inhibin B
Luteinizing hormone (LH): Stimulates the theca cells to produce progesterone and androstenedione (androgen), Surge induces ovulation, Fall in LH after ovulation causes the corpus luteum to degenerate
Estradiol: negative feedback to the pituitary gland to inhibit FSH release, Causes proliferation of the endometrium
Inhibin B: Negative feedback to the pituitary gland to inhibit FSH release
Progesterone: Causes differentiation of the endometrium in preparation for implantation

Distinguish between the following terms: Spermatocytogenesis, Spermiogenesis, Spermiation

Spermatocytogenesis: Spermatogonia form into spermatozoa
Spermiogenesis: Spermatids mature into spermatozoa
Spermiation: The release of mature spermatids from Sertoli cells into the seminiferous tubules, prior to their passage into the epididymis

Describe the phases of the menstrual cycle, respective changes in the endometrium, and the underlying hormonal basis

Phases in the ovarian cycle
- Follicular phase: FSH causes maturation of follicles
- Ovulation: LH surge causes ovulation
- Luteal phase: The remaining dormant follicle transforms into the corpus luteum under the influence of FSH and LH. The corpus luteum secretes progesterone
Phases in the Uterine cycle
- Proliferative phase: Estrogen from granulosa cells of the mature follicle causes proliferation of the endometrium
- Secretory phase: Progesterone from the corpus luteum causes differentiation of the endometrium. Glycogen, lipids, and proteins are secreted into the uterus and the cervical mucus thickens:
- Menstrual phase: Falling Estrogen and progesterone levels and increased prostaglandin production cause shedding of the uterine mucosa

Regarding fertilization describe the following: Prerequisites of fertilization, Phases of fertilization, The immediate results of fertilization

Prerequisites of fertilization: Capacitation, Acrosomal reaction, Zona reaction
Phases of fertilization: Penetration of the corona radiata, Penetration of the zona pellucida, Fusion of the oocyte and sperm membrane
Immediate results of fertilization: Restoration of diploid number of chromosomes, Sex determination, Initiation of cleavage (Mitosis), Metabolic activation of the cell

Reference Intervals ›

Biochemistry

ACTH	P: <80 ng/L
ALT	P: 5–35 U/L
Albumin	P: 35–50 g/L
Aldosterone	P: 100–500 pmol/L
Alk. phosphatase	P: 30–130 U/L
α-Amylase	P: 0–180 IU/dL
α-Fetoprotein	S: <10 kU/L
Angiotensin II	P: 5–35 pmol/L
ADH	P: 0.9–4.6 pmol/L
AST	P: 5–35 U/L
Bicarbonate	P: 24–30 mmol/L
Bilirubin	P: 3–17 μmol/L
BNP	P: <50 ng/L
CRP	P: <10 mg/L
Calcitonin	P: <0.1 mcg/L
Calcium (ionized)	P: 1.0–1.25 mmol/L
Calcium (total)	P: 2.12–2.60 mmol/L
Chloride	P: 95–105 mmol/L
Cholesterol	P: <5.0 mmol/L
VLDL	P: 0.128–0.645 mmol/L
LDL	P: <2.0 mmol/L
HDL	P: 0.9–1.93 mmol/L
Cortisol AM	P: 450–700 nmol/L
Cortisol Midnight	P: 80–280 nmol/L
CK ♂	P: 25–195 U/L
CK ♀	P: 25–170 U/L
Creatinine	P: 70–100 μmol/L
Ferritin	P: 12–200 mcg/L
Folate	S: 2.1 mcg/L
FSH	P: 2–8 U/L ♂; >25 menopause
GGT ♂	P: 11–51 U/L
GGT ♀	P: 7–33 U/L
Glucose (fasting)	P: 3.5–5.5 mmol/L
Growth hormone	P: <20 mu/L
HbA1C (DCCT)	B: 4–6%
HbA1C (IFCC)	B: 20–42 mmol/mol
Iron ♂	S: 14–31 μmol/L
Iron ♀	S: 11–30 μmol/L
Lactate (venous)	P: 0.6–2.4 mmol/L
Lactate (arterial)	P: 0.6–1.8 mmol/L
LDH	P: 70–250 U/L
LH	P: 3–16 U/L
Magnesium	P: 0.75–1.05 mmol/L
Osmolality	P: 278–305 mosmol/kg
PTH	P: 0.8–8.5 pmol/L
Potassium	P: 3.5–5.3 mmol/L
Prolactin ♂	P: <450 U/L
Prolactin ♀	P: <600 U/L
PSA	P: 0–4 mcg/mL
Protein (total)	P: 60–80 g/L
Red cell folate	B: 0.36–1.44 μmol/L
Renin (erect)	P: 2.8–4.5 pmol/mL/h
Renin (recumbent)	P: 1.1–2.7 pmol/mL/h
Sodium	P: 135–145 mmol/L
TBG	P: 7–17 mg/L
TSH	P: 0.5–4.2 mU/L
T4	P: 70–140 nmol/L
Free T4	P: 9–22 pmol/L
TIBC	S: 54–75 μmol/L
Triglycerides	P: 0.50–2.3 mmol/L
T3	P: 1.2–3.0 nmol/L
Troponin T	P: <0.1 mcg/L
Urate ♂	P: 210–480 μmol/L
Urate ♀	P: 150–390 μmol/L
Urea	P: 2.5–6.7 mmol/L
Vitamin B12	S: 0.13–0.68 nmol/L
Vitamin D	S: 50 nmol/L

Arterial Blood Gases

pH	7.35–7.45
PaCO₂	4.7–6.0 kPa
PaO₂	>10.6 kPa
Base excess	±2 mmol/L

Urine

Cortisol (free)	<280 nmol/24h
Hydroxyindole acetic acid	16–73 μmol/24h
Hydroxymethylmandelic acid	16–48 μmol/24h
Metanephrines	0.03–0.69 μmol/mmol cr.
Osmolality	350–1000 mosmol/kg
17-Oxogenic steroids ♂	28–30 μmol/24h
17-Oxogenic steroids ♀	21–66 μmol/24h
17-Oxosteroids ♂	17–76 μmol/24h
17-Oxosteroids ♀	14–59 μmol/24h
Phosphate (inorganic)	15–50 mmol/24h
Potassium	14–120 mmol/24h
Protein	<150 mg/24h
Protein/creatinine ratio	<3 mg/mmol
Sodium	100–250 mmol/24h

Haematology

WCC	4.0–11.0 ×10⁹/L
RBC ♂	4.5–6.5 ×10¹²/L
RBC ♀	3.9–5.6 ×10¹²/L
Hb ♂	130–180 g/L
Hb ♀	115–160 g/L
PCV ♂	0.4–0.54 L/L
PCV ♀	0.37–0.47 L/L
MCV	76–96 fL
MCH	27–32 pg
MCHC	300–360 g/L
RDW	11.6–14.6%
Neutrophils	2.0–7.5 ×10⁹/L (40–75%)
Lymphocytes	1.0–4.5 ×10⁹/L (20–45%)
Eosinophils	0.04–0.44 ×10⁹/L (1–6%)
Basophils	0–0.10 ×10⁹/L (0–1%)
Monocytes	0.2–0.8 ×10⁹/L (2–10%)
Platelets	150–400 ×10⁹/L
Reticulocytes	0.8–2.0% / 25–100 ×10⁹/L
Prothrombin time	10–14 s
APTT	35–45 s

Paediatric

Pulse Rate (bpm)
Neonate	140–160
Infant <1yr	120–140
1–5 years	110–130
5–12 years	80–120
>12 years	70–100
Respiratory Rate (tachypnoea)
0–2 months	≥60/min
2–12 months	≥50/min
1–5 years	≥40/min
>5 years	≥30/min
Blood Pressure (mmHg)
Term	65/45
1 year	75/50
4 years	85/60
8 years	95/65
10 years	100/70
Weight Formulas
3–12 months	(a + 9)/2 kg
1–6 years	2a + 8 kg
>6 years	(7a − 5)/2 kg
Haemoglobin (g/dL)
Term newborn	13–20
1 month	11–18
2 months	10–15
1–2 years	10–13
>2 years	11–14
MUAC (6 months–5 years)
Obese	>17.5 cm
Normal	13.5–17.4 cm
At risk	12.5–13.4 cm
Moderate malnutrition	11.5–12.4 cm
Severe malnutrition	<11.5 cm
Developmental Milestones
Social smile	1.5 months
Head control	4 months
Sits unsupported	7 months
Crawls	10 months
Stands unsupported	10–12 months
Walks	12–13 months
Talks	18 months
CSF WBC (/mm³)
Term newborn	0–25
>2 weeks	0–5

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