Anatomy of the breast and male reproductive systems Flashcards
What are breasts?
The breasts are paired structures on the anterior thoracic wall in the pectoral region.
Developmentally, breasts are part of the skin and are modified sweat glands.
The mammary gland is contained within the skin.
Male and female breast tissue is the same at birth.
Normally it only functions in biological females.
The changes occur due to the activity of hormones around puberty.
Stimulation by oestrogen, growth hormone and insulin like growth factor (IGF-1) cause the increase in size in females.
Male hormones prevent any further development.
What is the Gross anatomy of the breast?
Generally, overlie the 2nd- 6th ribs.
Anterior to the pectoral muscle.
Medial border – sternum
Lateral border – anterior or mid axillary line
Superior border – infraclavicular fossa
Inferior border – mid sternum
Inframammary fold
Breast parenchyma extends into the axilla.
Axillary tail
Nipple – surrounded by areola – pigmented
Dense fibrous tissue with smooth muscle fibres – erectile function.
Lies above the inframammary fold.
At the level of the 4th anterior rib.
The areola contains modified sweat glands.
Secretions lubricate during breast feeding.
The breast is divided into 4 quadrants plus a central area around the nipple.
1-3 o’clock – upper inner quadrant
3-6 o’clock – lower inner quadrant
6-9 o’clock – lower outer quadrant
9-12 o’clock - upper outer quadrant
What is the internal anatomy of the breasts?
Internally there are 15-20 lobes.
They are separated by connective tissue and adipose tissue.
Within each lobe there are around 20-40 lobules containing clusters of alveolar glands.
The alveolar glands produce milk.
Male breast tissue lacks these specialised lobules.
Milk passes from the alveolar gland to lactiferous ducts.
Lactiferous ducts open to the outside at the nipple.
What are Terminal ductal lobular unit?
The functional unit of the breast is the lobule.
Terminal ductal lobular unit (TDLU)
Consists of 10-100 acini, that drain into the terminal duct.
The terminal duct drains into larger ducts and finally into the main duct of the lobe (or segment), that drains into the nipple.
The breast contains 15-20 lobes, that each contain 20-40 lobules.
What is the Ductal system?
Lined with epithelium.
Reduced friction for milk flow.
Middle myoepithelial cells aid in movement of milk.
Basement membrane outer layer of duct in contact with intralobular stroma.
Breasts Ligaments
Suspensory ligaments from interlobular connective tissue to the dermis.
Cooper’s ligaments
Give breast shape
Not taut – movement
Relax with age/time
Breast ptosis
Blood supply in breasts
The breast is highly vascular.
Predominantly supplied by internal mammary arteries derived from internal thoracic artery.
Lateral thoracic and thoracoacromial arteries (branches of the axillary artery) as well as posterior intercostal arteries (branches of the thoracic aorta).
Venous drainage of the breast
Venous drainage of the breast is mainly by the axillary vein.
The subclavian, intercostal, and internal thoracic veins also aid in venous drainage.
Connections between the intercostal veins and the vertebral plexus allow metastasis of cancer to bones and to the nervous system.
Breasts: Nerve supply
Thoracic intercostal nerve – T3-5
Supraclavicular nerve from cervical plexus.
Breasts Lymphatic drainage
Originates from lobules to sub areolar plexus – Sappey’s Plexus
75% of lymph drainage to axillary nodes.
Drainage by 3 main routes
-Axillary/Lateral
-Fed by Sappey’s plexus to pectoral group of axillary nodes.
-Internal Mammary
-From lateral and medial
-Passes through pectoralis major.
-May lead across median plane to contralateral breast.
-Retromammary
-Posterior part of breast
75% of lymphatic drainage of breast goes to the axillary nodes.
The lymphatic drainage of the breast is of great importance in the spread of carcinoma
Breasts: Axillary lymph nodes
There are three levels of axillary lymph nodes:
level I -bottom level, below the lower edge of the pectoralis minor muscle.
level II- lies underneath/posterior the pectoralis minor muscle.
level III -above/medial the pectoralis minor muscle.
75% of lymph drainage is to the axillary nodes.
This is important to understand as it explains the spread of carcinoma.
Breast development and physiology
Thelarche – first sign of puberty and occurs at a mean age of 10 years
Mediated by levels of hormones
Oestrogen, progesterone, prolactin, growth hormone, thyroid and parathyroid hormones, insulin and cortisol
Oestrogen promotes increase in size by
Formation of mass of tissue under areola
Increase in size and pigmentation of areola
Development of lobular ducts
Breast development
Breasts of parous women and those never pregnant are different.
Expansion of acini only occurs during pregnancy when preparing for lactation.
During menopause lobules of parous women involute to pre-pregnancy composition and become identical to nulliparous women.
What are Cyclic changes?
Oestrogen develops lobular ducts.
Progesterone stimulates development of cells lining acini.
Lactation after childbirth in response to increased levels of prolactin.
Oxytocin after delivery controls milk ejection from acini cells.
During follicular/proliferative phase of menstrual cycle.
Oestrogen levels increase vascularity of breast tissue and stimulate proliferation of ductal and acinar tissue.
Effect sustained during luteal/secretory phase.
Progesterone levels increase and contribute to breast changes.
Dilation of ducts and conversion of acinar cells to secretory cells.
Breast volume may increase by 10 – 30mL
Length of menstrual cycle does not allow for complete regression of effects.
Breast growth continues until approx. 35 years
Breasts: Pregnancy + Post pregnancy
Breast remodels into milk-secreting organ.
Reaches ultimate mature developmental stage.
Increased oestrogen – lobules further differentiate.
Progesterone stimulates cells lining alveoli to produce milk.
Increased levels of prolactin – lactation.
Positive feedback
Lactation
Milk continuously secreted into alveolar lumen.
Stored until myoepithelial cells stimulated by suckling – oxytocin – triggers let-down reflex.
Post pregnancy:
Breast has capacity to regress to a resting stage after cessation of lactation and the undergoes same cycle of expansion and regression in subsequent pregnancies
Physiology – changes with age
Premenopausal
hormone levels decrease, glandular tissue shrivels or involutes, fat levels increase.
Postmenopausal
HRT can cause glandular tissue levels to increase.
Weight loss can lead to prominence of glandular tissue due to the decrease in the amount of surrounding fatty tissue.
What is The inguinal region?
The groin; junction between anterior abdominal wall and thigh
Inguinal canal 2.5-4cm long originates from deep to abdominal wall
Passes infero-medially towards genitalia
Natural weak point in abdominal wall; inguinal hernia
What is the Inguinal canal?
Formed between:
Anterior: external oblique muscle/fascia.
Posterior: internal oblique muscle/fascia.
Superior: transversus abdominus muscle.
Inferior: inguinal ligament.
Contains:
Spermatic cord structures (male) / round ligament and genital nerve (female)
Inguinal nerve
Narrow passage in inguinal region, follows distal half inguinal ligament (ASIS to symphysis pubis)
Between deep inguinal ring and superficial inguinal ring
Deep ring:
midway between ASIS and symphysis pubis, lateral to inferior epigastric vessels.
beginning of tubular evagination (‘pouch’) of abdominal wall transversalis fascia covering internal canal structures (internal spermatic fascia)
Superficial ring:
distal end, superficial to pubic tubercle.
Triangular opening through external oblique muscle
Tubular evagination of external oblique fascia (external spermatic fascia)
What are Inguinal hernias?
Protrusion of sac of peritoneum into the inguinal canal.
May contain omental fat or potentially bowel loops
Classified as:
Indirect:
through the deep inguinal ring (lateral to inferior epigastric vessels)
More common (especially in men)
Result of processus vaginalis remaining open (congenital)
Direct:
Through weakness of posterior inguinal wall .
Medial to inferior epigastric vessels.
More common in older men; acquired due to weakness.
Complications include bowel obstruction and potential strangulation and necrosis.
Functions of the male reproductive system
Functions as a system:
Production, maturation, and storage of sperm.
Delivery of sperm into the female reproductive system.
Excretion of urine.
Functions by organ(s)
Gonads - Testes: produce sperm and testosterone.
Ducts: transport, store, and mature sperm.
Accessory sex glands: secrete liquid portion of semen
Supporting structures -Penis: passage for excretion of urine and ejaculation of sperm
Structures of the male reproductive system
Scrotum
Testes
Ducts:
Ductus deferens
Ejaculatory ducts
Urethra
Accessory sex glands:
Seminal vesicles
Prostate gland
Bulbourethral glands
Penis
What is the Scrotum?
Pouch / sack supporting testes
(literally means bag)
Externally:
Loose skin, superficial fascia and smooth muscle separate by median ridge - raphe.
Attached to root of penis.
Internally:
Septum divides into two sacs with a testis.
Fascia/dartos muscle
What are the Testes/Testis/Testicles?
Paired oval glands.
Covered by white fibrous capsule that extends inwards to create internal compartments – 200-300 lobules.
Each lobule contains 1-3 coiled seminiferous tubules.
Seminiferous tubules -lined with spermatogenic cells .
Against the basement membrane of the tubules are spermatogonia.
Towards the lumen are layers of cells in advancing maturity, once mature they are released into the lumen.
Between the sperm cells are sustentacular cells (Sertoli) - protect and nourish spermatogenic cells, phagocytize degenerative cells, secret fluid and release the hormone inhibin .
Between the tubules are interstitial cells (Leydig) – secrete testosterone
Ducts of the male reproductive system
Seminiferous tubules
Epididymis
Ductus (vas) Deferens
Ejaculatory ducts
Urethra
Ducts of the testes
Continual release of sperm into the lumen of seminiferous tubules, and fluid secreted by the sustentacular cells propels them along the ducts.
Travel through convoluted seminiferous tubules to straight tubules distally and into a network of ducts called the rete testis.
Move then through efferent ducts into epididymis
What is the Epididymis / Epididymides (plural)?
Comma-shaped organ on posterior border of each testis.
Efferent ducts join epididymis superiorly at head .
Continue as tightly coiled ductus epididymis to form main body.
Smaller distal tail continues as ductus (vas) deferens
Ductus epididymis:
6m long if laid out (<4cm in length when coiled), 1mm diameter.
Site of sperm storage and maturation (up to a month)
Helps propel the sperm during arousal by peristaltic contraction of the smooth muscle into the ductus (vas) deferens
What are Ductus (vas) Deferens?
Distal to tail of epididymis on inferior aspect of testis.
Larger diameter, straighter
takes long course:
Superiorly along posterior aspect of epididymis and penetrates the inguinal canal
Supero-medially along inguinal canal (part of spermatic cord)
Through deep inguinal ring and into pelvic cavity,
Over ureter, and inferiorly along posterior aspect of bladder
Dilated most distally at ampulla where joins ejaculatory ducts
What are Ejaculatory ducts?
Formed at junction between ampulla of vas deferens and duct from seminal vesicles
Short - Approximately 2cm long
Pass from superior to prostate, inferiorly and anteriorly through prostate
Terminate into prostatic portion of urethra
Release sperm and secretions from seminal vesicles into the urethra prior to ejaculation
what is the Urethra?
The terminal duct
Conveys both sperm and urine.
Passes through:
inferior portion of the prostate,
deep muscles of the perineum
Penis
Opening is called the external urethral orifice
Accessory sex glands
Seminal Vesicles
Prostate
Bulbourethral glands
What are the Seminal vessels?
Paired pouch-like structures, convoluted
5cm long
Posterior/base of urinary bladder, anterior to the rectum
Secrete viscous/sticky fluid 60% semen volume
Alkaline – neutralise acids harmful to sperm
Rich in fructose - ATP production by sperm
Prostaglandins - sperm viability/motility
Fluid passed into ejaculatory duct
What is Prostate?
Doughnut shaped – size of a golf ball
Lies inferior to bladder, surrounds prostatic urethra
Grows slowly until puberty, then rapidly until around 30
Typically grows again from age of 45 (benign prostatic hyperplasia)
Produces milky slightly acidic fluid (around 25% semen volume) which aids sperm motility and viability
Citric acid; ATP production
Acid phosphatase
Proteolytic enzymes (regulated by testosterone):
Prostate-specific antigen (PSA); liquefies semen dissolves cervical mucous.
Pepsinogen, amylase, lysozyme, hyaluronidase.
Enters urethra through numerous prostatic ducts
What are Bulbourethral glands?
Also known as Cowper’s glands
Paired pea-sized organs
Inferior to prostate, within urogenital diaphragm either side of the urethra
Ducts open onto spongy urethra in root of penis
Produces fluids during arousal to protect sperm:
alkaline substance to neutralise acids in urethra and vagina.
mucous to lubricate tip of penis an urethra
Penis description
Contains urethra as passageway for urine and semen
Method to deliver semen
Consists of:
Body
Root
Glans
Supported by two ligaments continuous with fascia of penis:
Fundiform ligament; inferior part of linea alba.
Suspensory ligament of penis; from pubic symphysis
Structure of the body of the penis
Three cylindrical masses, each surrounded by fibrous tunica albuginea.
Consists of tissue permeated with sinuses for blood
Paired corpus cavernosum (hollow body) on dorsal surface
Penetrated by deep arteries of penis
Smaller corpus spongiosum on ventral and midline surface.
Contains spongy urethra, keeps patent during ejaculation
What is the Semen?
Mixture of sperm and semen made up of secretions from seminiferous tubules and accessory glands.
Typical ejaculation 2-5ml containing between 50-150 million sperm per ml
Acidic prostate secretion and alkaline from seminal vesicles result in slightly alkaline overall pH 7.2-7.7; helps to neutralise acid in urethra and vagina
Provides medium to transport and give nutrients to sperm
Also contains antibacterial agent to kill bacteria
Coagulates initially (similar to blood) but then re-liquefies due to enzymes from prostate to allow movement of sperm
Sperm production – involves Mitosis and Meiosis
Mitosis of spermatogonium – somatic cell division
Stem cell (46 pairs of chromosomes) – divides into two daughter cells (23 pairs of chromosomes).
Diploid cells – one stays a stem cell, one enters meiosis called primary spermatocyte.
Meiosis – two cycles of division.
At then end of Meiosis I cells now 2 secondary spermatocytes (23 chromosomes and a pair of duplicate chromatids).
Meiosis II produces 4 haploid spematids – each have 23 individual chromosomes (one from each pair).
Last step of Spermatogenesis – each spermatid matures into a spermatozoon (sperm) with a flagellum (tail)
Takes about 5 weeks to complete
