REPRODUCTIVE ANATOMY NOTES

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Reproductive Anatomy Notes

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Reproductive Anatomy Notes

the Reproductive Systems

· Distinguishes living from non-living things

· Sexual reproduction: two types of sex - male and female

· Initial cell is called zygote (formed when ovum is fertilized by spermatozoa)

· Female system forms ovum and matures it for fertilization

· Male system forms and transmits spermatozoa to the female

Gametes

· Specialized reproductive germ cells

· Male gametes: Spermatozoa

· Female gametes: Ova

· Contain genetic material/genes on chromosomes (pass inherited characteristics)

· Body cells: 46 chromosomes (23 pairs)

· Gametes: 23 chromosomes (one from each pair)

· Formed by meiosis

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Functions of Reproductive System

Female

· Formation of female gametes (ova)

· Reception of male gametes (spermatozoa)

· Provision of suitable environment for fertilization and fetal development

· Parturition (childbirth)

· Lactation (breastfeeding)

Male

· Production of male gametes (spermatozoa)

· Transmission of spermatozoa to the female

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Male Reproductive System

Organs

· 2 testes

· 2 epididymides

· 2 deferent ducts (vas deferens)

· 2 spermatic cords

· 2 seminal vesicles

· 2 ejaculatory ducts

· 1 prostate gland

· 1 penis

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Skrotum

· Pouch of deeply pigmented skin, fibrous tissue, connective tissue, and smooth muscle

· Divided into two compartments, each containing:

· 1 testis

· 1 epididymis

· Spermatic cord

· Lies below pubic, in front of upper thigh, behind penis

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Testees

· Male reproductive gland (similar to ovaries)

· Size: 4.5 centimeters long, 2.5 centimeters wide, 3 centimeters thick

· Suspended in scrotum by spermatic cord

· Surrounded by three layers of tissue:

Tunica Vaginalis

· Outer covering (double membrane)

· Down growth of abdominal and pelvic peritoneum

· Takes blood, lymph, nerves, and deferent duct during descent

· Becomes detached from abdominal peritoneum

· Descent complete by 8th month of fetal life

Tunica Albuginea

· Fibrous covering beneath tunica vaginalis

· Ingrowths form septa dividing testes into lobules

Tunica Vasculosa

· Network of capillaries supported by delicate connective tissue

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Structure of Testees

· 200 to 300 lobules in each testis

· Each lobule has 1 to 4 convoluted loops called seminiferous tubules (germinal epithelial cells)

· Between tubules: Interstitial cells of Leydig (secrete testosterone during puberty)

· At upper part, tubules combine to form epididymis (long coiled tube, 6m in length)

· Leaves scrotum as deferent duct/vas deferens in spermatic cord

· Blood and lymph pass through spermatic cord

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Function of Testees

· Sperm produced in seminiferous tubules

· Mature as they pass through epididymis and stored there

· Hormone controlling: F.S.H

· Mature sperm has: Head (D.N.A and enzyme), Body (mitochondria), Tail (motion)

· Spermatogenesis takes place at 3 degrees Celsius below body temperature (cooled by outer placement and little fat in scrotum)

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Spermatic Cord

· Suspends testes in scrotum

· Each has: testicular artery, vein, lymphatic, testicular nerve, vas deferens

· Covered in smooth muscle, connective tissue, fibrous tissue

· Extends through inguinal canal to testes on posterior wall

Blood/Nerve Supply

· Artery: Testicular artery from abdominal ay-or-tuh

· Vein: Left from left renal vein, Right from inferior vena cava

· Lymph: Nodes around ay-or-tuh

· Nerve: 10th and 11th thoracic nerve

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Vas Deferens

· 45 centimeters long

· Runs up from testes through inguinal canal

· Ascends to posterior wall of bladder

· Joins seminal vesicle to form ejaculatory duct

Seminal Vesicles

· Two small pouches

· Join vas deferens to form ejaculatory duct

· Contract and expel stored seminal fluid during ejaculation

· Forms 60% of semen bulk

· Has nutrients for sperm

Ejakulatoree Duct

· Two ducts, about 2 centimeters long each

· Formed by union of seminal vesicles and vas deferens

· Pass through prostate gland and joins prostatic urethra

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Prostate Gland

· Surrounds first part of urethra

· Secretes thin milky fluid (makes 30% of semen)

· Has clotting enzymes that thicken semen in vagina (retained in cervix)

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Urethruh

· Used for flow of urine and semen

· 19 to 20 centimeters long

· Three parts:

1. Prostatic Urethra

· From bladder to prostate gland

2. Membranous Urethra

· Shortest and narrowest part

· From prostate gland to bulb of penis through perineal membrane

3. Spongy/Penile Urethra

· Lies in corpus spongiosum of penis

· Terminates at external opening in glans penis

Urethral Sphincters

· Internal sphincter: at neck of bladder

· External sphincter: skeletal muscle surrounding membranous part

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Penis

· Has root and body

· Root in perineum, body surrounds urethra

· Formed by three cylindrical muscles of erectile tissue and smooth muscle

· Supported by fibrous tissue and covered by skin

· Has rich blood supply

· Tip: Glans penis

· Skin fold on glans: Foreskin/Prepuce

Corpora Cavernosa

· Two lateral columnar muscles

Corpus Spongiosum

· One columnar between the two above

Blood and Nerve Supply

· Artery: Deep, dorsal, and bulbar artery (branch of internal pudendal artery)

· Vein: Internal pudendal and internal iliac vein

· Nerve: Autonomic and somatic nerve

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Ejakulashun

· Occurs at male orgasm

· Sperms expelled from epididymis to vas deferens to ejaculatory duct to urethra

· Propelled by rhythmic contraction of smooth muscle

· Prostate and seminal vesicle muscles contract

· Sperm makes 10% of semen

· Semen is slightly alkaline (neutralizes vaginal acid)

· Normal ejaculation: 2 to 5 ml semen, 40 to 100 million spermatozoa/ml

· If not ejaculated, sperm lose fertility after several months and are reabsorbed

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Blood-Testis Barrier

· Walls of seminiferous tubules lined by primitive germ cells and Sertoli cells

· Forms blood-testis barrier

· Can pass: steroids, proteins, glucose, androgen, estrogen

· Prevents autoimmune reaction

· Sertoli cells produce: Androgen-binding protein, Inhibin, M.I.S (Mullerian Inhibitory Substance)

· Convert androgen to estrogen

· Inhibin inhibits F.S.H secretion

· M.I.S causes regression of Mullerian duct in male during fetal life

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Semen Composition

· Seminal vesicles: 60%

· Prostate: 30%

· Cowper's glands and urethral glands: 10%

· Fructose, prostaglandin, ascorbic acid, flavin

· Citric acid, cholesterol, zinc, fibrinolysin

· Speed: 3 millimeters/min

· Takes 30 to 60 minutes

· Volume: 2-5ml

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Erection

· Stimulated by: Tactile, visual, auditory, and olfactory stimulation

· Dilation of penile arteries

· Veins compressed to no outflow

· Afferent impulses from genitals to lumbar spinal cord

· Descending tracts mediate erection (psychological stimulation)

· Efferent parasympathetic fibers in pelvic splanchnic nerve to vasodilation

· Terminated by sympathetic nerve

Ejakulashun (Spinal Reflex)

· Afferent receptors for touch in glans penis to spinal cord through internal nerves

· Emission: sympathetic response to contraction of smooth muscle (hypogastric nerve)

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Female Reproductive System

External Genitalia (Vulva)

1. Mons Pubis/Veneris

· Firm cushion of fat over symphysis pubis

· Covered by hair from puberty

· Role: Sensuality, protects symphysis pubis during copulation

2. Labia Majora (Greater Lips)

· Two prominent longitudinal folds of fat and areolar tissue

· Arise from lower margin of mons veneris, run downwards/backwards to perineum

· Outer aspect: pubic hair from puberty

· Inner aspect: smooth and moist

· Forms anterior border of perineal body, protects inner vulva

3. Labia Minora (Lesser Lips)

· Two thin longitudinal folds of hairless skin covered with thin membrane

· Outer surface joins inner edge of labia majora

· Anteriorly: separate to enclose clitoris

· Posteriorly: fuse to form fourchette (posterior part of vaginal orifice)

4. Vestibule

· Oval-shaped area enclosed by labia minora

· Extends from clitoris to fourchette

· Contains: external urethral meatus, vaginal introitus, Bartholin glands openings

· Bartholin glands: lubricate vulva

· Skene's glands: lubricate urethra opening

5. Clitoris

· Small rudimentary sexual organ

· Comprises erectile tissue, covered by thin epidermis, highly vascular, extremely sensitive

· Visible knob-like part above urethra meatus

· Comprises: prepuce (superiorly) and frenulum (inferiorly)

· Functions: Sexual excitement/arousal, orgasm, facilitates vulva stretching during childbirth

6. Hymen

· Thin membrane partly occluding vaginal opening

· Presence in adulthood indicates virginity

· Normally torn during first copulation, vigorous exercise, tampon use

· Remaining tags: Carunculae myrtiformes

7. Perineum

· Triangular-shaped area

· Anterior-superior: fourchette, Posterior-inferior: anus

· Comprises pelvic floor muscles, fat, connective tissue

· Injury almost inevitable during delivery

Blood Supply, Lymphatics, Nerves

· Arteries: Internal and external pudendal arteries

· Lymph: Inguinal glands to iliac glands

· Nerves: Pudendal nerve branches, vaginal nerves (parasympathetic fibers, vasodilator effect)

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Internal Genitalia

1. Vajina

· Distensible fibromuscular tubular structure connecting external and internal genitalia

· Length: approximately 10 centimeters, Diameter: approximately 2.5 centimeters

· Canal passes upwards and backwards

Relations:

· Anteriorly: Urinary bladder and urethra

· Posteriorly: Pouch of Douglas, rectum, perineal body

· Superiorly: Cervix and uterus

· Inferiorly: External genitalia

· Laterally: Upper 2/3 - pelvic fascia, lower 1/3 - pelvic floor

Structure:

· Vault: Upper end of vagina

· Walls: Anterior (7.5 centimeters), Posterior (10 centimeters)

· Fornices (4): Anterior, Posterior (largest), two Lateral

Layers:

1. Mucosa (innermost): Stratified squamous epithelium, allows exudates to moisten vagina

2. Muscle layer: Inner circular fibers, outer longitudinal fibers (allow stretching)

3. Pelvic fascial (outermost): Surrounds vagina and adjacent pelvic organs

· Walls have transverse folds called Rugae (allow maximum stretching)

Normal Vaginal State:

· Warm, moist, pinkish appearance

· Vaginal fluid: acidic (pH 4.5)

· Acidity from Doderlein's bacilli (lactobacilli) acting on glycogen

· Prevents growth of pathogenic organisms during childbearing period

· Oestrogen produces glycogen in vaginal cells

Functions:

· Allows menstrual fluid to flow out

· Receives penis and ejected sperms during copulation

· Provides exit for fetus during birth

Blood Supply: Branches of internal iliac artery (descending branch of uterine artery, vaginal artery)

Lymph: Inguinal, internal iliac, sacral glands

Nerve: Lee Frankenhauser Plexus (pelvic plexus)

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2. Serviks (Neck of Womb)

· Situated between uterine cavity and upper end of vagina

· Divided into:

· Supravaginal portion (above vagina)

· Infravaginal portion (protrudes into vault)

Areas:

1. Internal cervical os: Opening between isthmus and cervical canal

2. Cervical canal: Spindle-shaped, narrow at ends, wider in middle

3. External cervical os: Opening at lower end of cervix to vagina

Layers:

1. Cervical endometrium (inner lining): Mucous membrane with tall columnar epithelial cells, mucus-secreting glands, folded into Arbor Vitae (assists sperm passage)

2. Muscle layer: Thinner continuation of uterine muscle, longitudinal and circular fibers, embedded in collagen (facilitates stretching/dilatation during labour)

Functions:

· Prevents easy ascent of infectious organisms to uterus

· Remains closed prenatally for fetal development

· Allows passage of bloody mucoid discharge (indicates true labour)

· Facilitates expulsion of fetus during birth process

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3. Uteruss

· Thick-walled hollow muscular organ, pear-shaped, flattened anteriorly/posteriorly

· Located in pelvic cavity between bladder and rectum

Measurements:

· 7.5 centimeters long, 5 centimeters wide, 2.5 centimeters thick

· Weight: 30-40g (before first pregnancy), approximately 60g (thereafter)

· Cervix forms lower 1/3 of uterus

Position: Anteversion-anteflexion (leans forward and bends forward upon itself)

Specific Parts:

1. Fundus: Dome-shaped upper wall, above uterine tube insertion

2. Cornua: Upper outer angles where uterine tubes join

3. Corpus (Body): Below cornua to narrowing (4 centimeters long), triangular uterine cavity

4. Isthmus: Narrow area between uterine cavity and cervix (~0.7 centimeters long)

Layers/Walls:

1. Perimetrium (outermost): Double serous membrane (peritoneum extension)

· Anteriorly: covers uterus to internal cervical os, reflected to bladder forming uterovesical pouch

· Posteriorly: covers uterus completely, reflected to rectum forming recto-uterine pouch of Douglas

· Laterally: covers fundus, forms broad ligaments

2. Myometrium (middle): Muscular layer

· Thickest at fundus and body, thinner at isthmus and cervix

· Fibers interlace in all directions (fundus/body)

· More circular fibers (isthmus/cervix)

3. Endometrium (innermost): Ciliated epithelium with cuboidal cells, alkaline mucus-secreting glands, capable of rapid regeneration

Relations:

· Anteriorly: Uterovesical pouch, urinary bladder

· Posteriorly: Recto-uterine pouch of Douglas, rectum

· Superiorly: Intestines

· Inferiorly: Cervix and vagina

· Laterally: Broad ligaments, uterine tubes, ovaries, uterine blood vessels, lower ureters

Functions:

· Prepares for pregnancy monthly

· Shelters and nourishes fetus

· Expels products of conception through labour

Blood Supply: Uterine artery, Ovarian artery (highly vascular)

Nerve Supply: Autonomic nervous system (sympathetic and parasympathetic through pelvic plexus)

Lymph: Body to internal iliac glands; Cervix to various pelvic lymph glands

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Uterine Supports

Pelvic floor is main supportive factor

Cervical Level Ligaments:

1. Transverse cervical ligaments (Cardinal/Mackenrodt's): Lateral aspect of cervix to pelvic side walls

2. Pubocervical: Anterior cervix to under bladder to anterior pubic bones (pulls cervix forward)

3. Uterosacral: Posterior cervix to sacrum (pulls cervix backward)

· Pubocervical + Uterosacral maintain uterus in position

4. Broad ligaments: Double peritoneum fold draping over uterine tubes, extends from lateral uterus to pelvic side walls

5. Round ligaments: Cornua to inguinal canal to labia majora (maintains anteverted position minimally)

6. Ovarian ligaments: Cornua (posteriorly to tubes) to ovaries

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4. Uterine Tubes (Fallopian Tubes/Salpinges/Oviducts)

· Two thin tubular structures, approximately 10 centimeters long each

· Run laterally from cornua to ovaries

Parts:

1. Interstitial/Intramural: Within uterine wall (~1.25 centimeters long, 1 millimeters lumen)

2. Isthmus: Narrowest part adjoining uterus (~2.5 centimeters long)

3. Ampulla: approximately 5 centimeters long, 2 to 3 centimeters lumen

4. Infundibulum: Funnel-shaped fringed end with fimbriae (finger-like projections), longest is ovarian fimbria (directs ovum to tube)

Layers:

1. Innermost (Mucosa): Ciliated cuboidal epithelium with plicae (folds) that slow ovum movement; goblet cells produce glycogen-containing secretions

2. Middle (Muscular): Thin muscular coat with inner circular/outer longitudinal fibers (peristaltic action conveys ovum)

3. Outermost: Peritoneum continuation (inferior surface uncovered)

Relations:

· Anteriorly/Superiorly/Posteriorly: Peritoneal cavity, intestines

· Inferiorly: Broad ligaments, ovaries

· Laterally: Pelvic side walls

· Medially: Uterus

Functions:

· Facilitates passive movement of ovum from ovary to uterine cavity

· Provides site for conception

· Provides nourishment for fertilized ovum

· Receives spermatozoa

Blood/Lymph/Nerve: Uterine and ovarian arteries, lumber glands, ovarian plexus

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5. Ovaries

· Two glandular organs in peritoneal cavity, attached to broad ligaments

· Weight: 4-8g each (right slightly larger)

Development:

· At birth: 200,000 to 400,000 primordial follicles

· Some develop into graafian follicles

· From puberty: ovulation occurs monthly

Relations:

· Anteriorly: Broad ligaments

· Superiorly: Uterine tubes

· Posteriorly: Intestines

· Laterally: Infundibulo-pelvic ligament, pelvic side walls

· Medially: Uterus, ovarian ligament (~2.5 centimeters long)

Note: Ovaries + uterine tubes + mesenteries = Adnexa/Appendages

Structure:

· Medulla (inner): Supporting framework with blood/lymphatic vessels, nerves

· Entry site: Hilum, attached to broad ligament = Mesovarium

· Cortex (outer): Functional part with ovarian follicles, surrounded by connective tissue, outer fibrous layer = Tunica albuginea, covered by Germinal epithelium (peritoneum modification)

Functions:

· Produces ova throughout procreation period

· Produces estrogen and progesterone for endometrial preparation

Blood Supply: Ovarian arteries; Right ovarian vein to inferior vena cava, Left to left renal vein

Lymph/Nerve: Same as uterine tubes

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Breasts (Mammary Glands)

Description

· Compound secreting glands (glandular parenchyma, fibrous tissue, adipose tissue)

· Lie on anterior chest over pectoral muscle

· Accessory glands of female reproductive system

· Size determined by fat deposit

Development

· From 5 weeks gestation: mammary structures over entire anterior aspect (clavicle to inguinal)

· Most degenerate, leaving two on anterior chest

· At birth: nipple + few vestigial ducts

· From puberty: Oestrogen and progesterone stimulate growth

· Mature: extend from 2nd to 6th rib vertically, sternum to anterior axillary folds horizontally

· Axillary tail: Radiates upwards and outwards

· Nipple: Smooth muscle, erectile tissue; base has Areola (hyperpigmented area)

Structure

· 20 lobes per breast

· Separated by fibrous septae (runs from behind nipple to pectoral muscle)

· Each lobe has numerous lobules

· Each lobule has collection of alveoli

· Each alveolus has Acini cells (produce milk under Prolactin influence)

· Lobules to small ducts to Lactiferous ducts to Lactiferous sinuses/Ampullae (milk reservoirs)

· Milk propelled by oxytocin acting on myoepithelial cells

· Lactiferous tubules lead milk to infant's mouth

· Terminal ducts contract to prevent automatic milk flow

Blood Supply

· Arteries: Internal mammary, upper intercostal (thoracic), axillary arteries

· Veins: Circular veins behind nipple to internal mammary and axillary veins

· Richly supplied prenatally and during breastfeeding

Lymph Drainage

· Extensive, communicates between breasts

· Through internal mammary nodes to axillae and mediastinal lymph vessels/nodes

Nerve Supply

· Sensory nerve endings around nipple (facilitates milk ejection)

· 4th, 5th, 6th thoracic nerves (sympathetic fibers)

Function

· Nourishment of infant for first 6 months

Caution

· Breast cancer: 2nd malignant killer disease in females

· Self breast examination recommended (a week after menses)

· Men should also examine regularly (late diagnosis often fatal)

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Bony Pelvis

Parts of Pelvis

1. Sacrum

2. Ilium

3. Ischium

4. Pubic bone

5. Pubic symphysis

6. Acetabulum

7. Obturator foramen

8. Coccyx

· Terminal line/Pelvic brim (red line)

True Pelvis

· Comprises: Brim, Inlet, Cavity, Outlet

· Provides bony canal for fetus to pass through

· In upright gynaecoid pelvis: Brim 60°, Cavity 30°, Outlet 15°

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Brim/INLET

Determines pelvis shape

Landmarks (8):

· Anteriorly: Upper inner borders of symphysis pubis, body of pubic bone, superior ramus of pubic bone

· Laterally: Iliopectineal eminence, Iliopectineal line

· Posteriorly: Sacral-iliac joint, Alae of sacrum, Sacral promontory

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Cavity

· Lies between inlet and outlet

· Generally circular

· Anterior: symphysis pubis, bodies of ischium, part of ilium (4 centimeters deep)

· Posterior: hollow of sacrum (12 centimeters deep)

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Outlet

Anatomical:

· Anteriorly: Pubic arch, inferior pubic rami

· Laterally: Ischial tuberosities, sacrotuberous ligaments, sciatic notches, ischial spines

· Posteriorly: Coccyx

Obstetrical:

· Diamond-shaped

· Space available for fetal passage (narrow pelvic strait)

· Lies between: sacrococcygeal joint, ischial spines, pubic arch

· Ischial spines level = upper transverse border

· Intertuberous space = lower transverse border

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Diameters of Pelvic Brim

1. Anteroposterior (Obstetrical Conjugate)

· Sacral promontory center to upper inner border of symphysis pubis

· 11 centimeters (excludes bone thickness)

2. Oblique (x2)

· One sacro-iliac joint to opposite iliopectineal eminence

· Named according to sacro-iliac joint

· 12 centimeters each

3. Transverse

· Furthest points apart on each iliopectineal line

· 13 centimeters

4. Sacro-cotyloid (x2)

· Sacral promontory to iliopectineal eminence on each side

· 9.0 to 9.5 centimeters

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Cavity Diameters

· All estimated 12 centimeters each (circular area)

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Outlet Diameters

1. Anteroposterior

· Lower border of symphysis pubis to sacrococcygeal joint

· 13 centimeters (represents pelvic strait)

2. Oblique (x2)

· Estimated 12 centimeters

3. Transverse (Bispinous)

· Between ischial spines

· 10 to 11 centimeters (universally accepted as 11 centimeters)

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Other Diameters

1. Diagonal Conjugate

· Lower border of symphysis pubis to sacral promontory (digital pelvic assessment)

· approximately 13 centimeters

2. True/Anatomical Conjugate

· Sacral promontory center to highest point of symphysis pubis (X-ray)

· Includes bone thickness

· 12 centimeters

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Types/Classification of Pelvis

1. Inherited (Genetical link, racial characteristics)

1. Ginecoid (50% of women)

· Normal pelvis for childbirth

· Average height/build, shoe size 4+

· Features: Rounded brim, generous forepelvis, straight side walls, shallow/round cavity, broad/curved sacrum, blunt ischial spines, wide sciatic notch, sub-pubic angle 90°

2. Justo Minor

· Gynaecoid pelvis with all diameters proportionally reduced

· Height less than 150 centimeters, shoe size less than 4

3. Android (20% of women, male pelvis)

· Short, heavily built, hirsute

· Features: Heart-shaped brim, narrow forepelvis, convergent side walls, funnel-shaped/deep cavity, prominent ischial spines, narrow/deep sciatic notch, straight sacrum, acute sub-pubic angle ( less than 90°)

4. Anthropoid (25% of women, ape-like)

· Tall (height greater than 158 centimeters), narrow shoulders

· Features: Long oval brim (A-P greater than transverse), narrowed forepelvis, divergent side walls, narrow/long sacrum (6 vertebrae), well curved

5. Platyelloid (5% of women, flat pelvis)

· Features: Kidney-shaped brim, divergent side walls, shallow cavity, flat sacrum

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Pelvic Floor

· Soft tissues filling pelvic outlet

· Muscles hang from pelvic side walls, meet at perineal body (sling-like hammock)

· Penetrated by three canals: Anal (posterior), Vagina (medial), Urethra (anterior)

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Superficial Muscle Layer (5 muscles)

1. External Anal Sphincter: Surrounds anus, voluntarily controls defecation, attached to coccyx posteriorly

2. Transverse Perineal: Each from ischial tuberosity to perineum center

3. Bulbocavernosus (pair): From perineum, forward around vagina, inserted to corpora cavernosa of clitoris

4. Ischiocavernosus (pair): From ischial tuberosity, along inferior pubic rami, inserted to corpora cavernosa

5. Membranous Sphincter of Urethra: Fibers passing above/below urethra from pubis to pubis (not true sphincter, closes urethra when contracted)

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Deep Muscle Layer (3 pairs)

1. Pubococcygeus (with puborectalis): From posterior aspect of inferior pubic rami, around rectum to coccyx/lower sacrum; some fibers to perineal body

2. Ischiococcygeus: From ischial spines and sacroiliac fascia, attached to coccyx, lower sacrum, sacrotuberous ligaments

3. Iliococcygeus: From fascia covering obturator internus, directed posteriorly/medially, converges with pubococcygeus to coccyx

· Pubococcygeus + Puborectalis + Iliococcygeus = Levatores Ani

· Stabilize pelvic structures, support against increased abdominal pressure

· Ischiococcygeus + Levatores Ani = Pelvic Diaphragm

· Triangular ligament: Tissue filling triangular space between bulbocavernosus, ischiocavernosus, transverse perineal muscle

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Functions of Pelvic Floor

· Supports pelvic and abdominal organs

· Copulation: ischiocavernosus contraction (arousal), bulbocavernosus contraction (diminishes vaginal orifice)

· Controls micturition and defecation

· Facilitates fetal movement through birth canal

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Fetal Skull

Definition

Bony structure of fetal head comprising vault, face, and base

Rationale for Learning

· Skull encloses delicate brain (may be traumatized during labour)

· Head slightly larger than true pelvis (adaptation required)

· Head most difficult part to be born

· Standardized areas help diagnose labour course

Skull Development

· Vault bones: from membranes

· Face bones: from cartilage

· Ossification starts at 8th week of intrauterine life

· At birth: face bones ossified/fused, vault bones flat and pliable

· Vault bones ossify from center outward (ossification centers = eminences/protuberances)

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Regions and Landmarks

Vault (largest, dome-shaped, compressible part):

· Anteriorly: orbital ridges

· Laterally: temporal bones

· Posteriorly: nape of neck

Areas:

1. Sinciput/Brow

2. Vertex

3. Occiput

Fontanelles:

Anterior Fontanelle:

· Broad (3 to 4 centimeters long, 1.5 to 2 centimeters wide)

· Kite/diamond shaped

· Cerebral vessel pulsation felt through it

· Closes by 18 months

Posterior Fontanelle:

· Triangular shaped, quite small

· Identified per vaginally

· Closes by 6 weeks

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Diameters of Fetal Skull

Anteroposterior Diameters (6)

1. Suboccipitobregmatic (S.O.B) = 9.5 centimeters

· Below occipital protuberance to center of anterior fontanelle

2. Suboccipitofrontal (S.O.F) = 10 centimeters

· Below occipital protuberance to center of frontal suture/sinciput

3. Occipitofrontal (of) = 11.5 centimeters

· Occipital protuberance to glabella

4. Submentobregmatic (S.M.B) = 9.5 centimeters

· Junction of chin and neck to center of bregma

5. Submentovertical (S.M.V) = 11.5 centimeters

· Junction of chin and neck to highest point on vertex

6. Mentovertical (M.V) = 13.5 centimeters

· Tip of chin to highest point on vertex

Transverse Diameters (2)

1. Bitemporal = 8.2 centimeters

· Furthest points of coronal suture at temples

2. Biparietal = 9.5 centimeters

· Between two parietal eminences

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Introduction to Genetics

Objectives

· Explain structural relationship between chromosomes, genes, and D.N.A

· Describe molecular structure of D.N.A

· Explain autosomes and sex chromosomes

· Define genome, haploid, diploid, karyotype

Introduction

· All living things reproduce

· Babies inherit information through D.N.A

· D.N.A in nucleus organized into genes

· Genes are part of chromosomes

· All genetic material in cell = Genome

· Genetics: Study of genes

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Chromosomes

· All cells except R.B.C have genetic material

· In resting cell: not visible

· During cell division: visible as sausage-shaped chromosomes

· Each chromosome is one of a pair (one from mother, one from father)

· Human cells: 46 chromosomes (23 pairs)

Terms:

· Diploid: 23 pairs (46 chromosomes)

· Haploid: 23 chromosomes (gametes/sperm/ova)

· Homologous chromosomes: From same pair

· Karyotype: Complete set of chromosomes

· Autosomes: First 22 pairs of chromosomes

· Sex chromosomes: 23rd pair (X.X or X.Y)

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Genetics

· Each gene has information codes to make specific protein

· Each code for only one specific protein

· 24,500 genes in cell

· Genes exist in pairs called locus

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Nucleic Acids (R.N.A and D.N.A)

· Linear polymers of nucleotides linked by phosphate

Nucleotide Composition:

1. Nitrogen base: Purines (Adenine, Guanine) and Pyrimidines (Uracil, Cytosine, Thymine)

2. Pentose sugar: Ribose and Deoxyribose

3. Phosphate: Phosphoric acid

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Structure of D.N.A

· Forms a helix (double-stranded)

· Right-handed helix

· Phosphate forms hydrophilic backbone

· Nitrogen bases form hydrophobic interior

· Forms major and minor grooves

· Each base pairs with complementary strand

· Strands: 1m long

· Sugar: Deoxyribose

· Twists on histones (proteins) to three-dimensional figure to chromatids to chromosomes