Anatomy
MBBS Anatomy question bank: general anatomy and osteology, regional gross anatomy (upper limb, lower limb, thorax, abdomen, pelvis, head and neck), neuroanatomy, histology and embryology.
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Definition
The bony pelvis is the ring of bones connecting the trunk to the lower limbs; the pelvic diaphragm is the muscular floor supporting the pelvic viscera.
Bony Pelvis
- Two hip bones (ilium, ischium, pubis)
- Sacrum + coccyx
- Pelvic brim divides greater (false) & lesser (true) pelvis
Pelvic Diaphragm
- Formed by levator ani + coccygeus
- Funnel-shaped muscular floor
- Supports the pelvic organs
Functions
- Supports the viscera
- Transmits body weight to the lower limbs
- Forms the birth canal (female)
The bony ring transmits weight; the muscular diaphragm forms its floor. Part Structure Bony ring Hip bones, sacrum, coccyx Floor Levator ani, coccygeus Division Pelvic brim Applied
- Pelvic fracture
- Prolapse (weak pelvic diaphragm)
🔑KEY POINTS TO REMEMBER- Bony pelvis: hip bones + sacrum + coccyx; brim divides true/false.
- Pelvic diaphragm = levator ani + coccygeus.
- Supports viscera, forms birth canal.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The urinary bladder is a muscular reservoir for urine in the pelvis; the urethra conveys urine to the exterior.
Bladder
- Detrusor muscle wall
- Trigone (between ureters & urethra)
- Empty — pelvic; full — rises into abdomen
- Apex, base, neck
Male Urethra (~20 cm, 3 parts)
- Prostatic
- Membranous (shortest, narrowest)
- Spongy (penile, longest)
Female Urethra (~4 cm)
- Short and straight → more UTIs
Urine collects in the bladder and drains through the urethra. Feature Male Female Length ~20 cm ~4 cm Parts 3 1 UTIs Less More Applied
- Catheterisation
- Urethral rupture (male, membranous part)
🔑KEY POINTS TO REMEMBER- Bladder: detrusor wall, trigone; rises when full.
- Male urethra ~20 cm (prostatic, membranous, spongy).
- Female urethra ~4 cm → more UTIs.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The rectum and anal canal are the terminal GI tract; the perineum is the diamond-shaped region below the pelvic diaphragm.
Rectum
- Continuation of the sigmoid colon
- No taeniae or appendices epiploicae
- Stores faeces
Anal Canal
- Upper 2/3 — endoderm (visceral, painless)
- Lower 1/3 — ectoderm (somatic, painful)
- Dentate (pectinate) line divides them
Perineum (2 triangles)
- Urogenital triangle (anterior)
- Anal triangle (posterior)
- Perineal body — central tendon
The perineum splits into a urogenital and an anal triangle. Anal canal Above line Below line Origin Endoderm Ectoderm Nerve Autonomic Somatic Pain No Yes Applied
- Haemorrhoids (internal vs external)
- Anal fissure (painful, below the line)
🔑KEY POINTS TO REMEMBER- Rectum stores faeces; no taeniae.
- Anal canal split by dentate line (visceral above, somatic below).
- Perineum: urogenital + anal triangles, perineal body.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The female reproductive organs in the pelvis include the ovaries, uterine tubes, uterus and vagina.
Organs
- Ovaries — produce ova & hormones
- Uterine (fallopian) tubes — site of fertilisation
- Uterus — anteverted, anteflexed; body, fundus, cervix
- Vagina — canal to the exterior
Uterine Support
- Pelvic diaphragm (levator ani)
- Ligaments (broad, round, uterosacral, cardinal)
Blood Supply
- Uterine artery (from internal iliac)
- Crosses the ureter (‘water under the bridge’)
The ovum travels ovary → tube → uterus, then out via the cervix and vagina. Organ Function Ovary Ova, hormones Uterine tube Fertilisation Uterus Implantation Applied
- Ureter injury in hysterectomy
- Ectopic pregnancy (uterine tube)
🔑KEY POINTS TO REMEMBER- Organs: ovaries, tubes, uterus, vagina.
- Uterus anteverted & anteflexed; supported by levator ani + ligaments.
- Uterine artery crosses the ureter.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The male reproductive organs include the testes, epididymis, vas deferens, seminal vesicles, prostate and penis.
Organs
- Testes — sperm + testosterone (in the scrotum)
- Epididymis — sperm maturation/storage
- Vas deferens — conveys sperm
- Seminal vesicles + prostate — secretions
Pathway of Sperm
- Seminiferous tubules → epididymis → vas deferens
- → ejaculatory duct → urethra → penis
Sperm mature in the epididymis and travel out via the vas, duct and urethra. Organ Role Testis Sperm, testosterone Epididymis Maturation Prostate Seminal fluid Applied
- Vasectomy (vas deferens)
- Benign prostatic hyperplasia (prostate)
🔑KEY POINTS TO REMEMBER- Organs: testes, epididymis, vas, seminal vesicles, prostate, penis.
- Sperm path: tubules → epididymis → vas → duct → urethra.
- Vasectomy at the vas; BPH at the prostate.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The levator ani is the main muscle of the pelvic diaphragm, forming a muscular sling that supports the pelvic viscera.
Parts
- Pubococcygeus
- Puborectalis (maintains the anorectal angle)
- Iliococcygeus
Functions
- Supports the pelvic organs
- Maintains continence (anorectal angle)
- Resists raised intra-abdominal pressure
The levator ani slings up the viscera and keeps the anorectal angle. Part Role Puborectalis Anorectal angle Pubococcygeus Support Iliococcygeus Support Applied
- Weakness → prolapse, incontinence
- Damaged in childbirth
🔑KEY POINTS TO REMEMBER- Levator ani: pubococcygeus, puborectalis, iliococcygeus.
- Supports viscera + maintains continence.
- Childbirth damage → prolapse.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The male and female pelves differ structurally, mainly adapting the female pelvis for childbirth.
Female Pelvis
- Wider and shallower
- Rounded / oval inlet
- Wider subpubic angle (>90°)
- Adapted for childbirth
Male Pelvis
- Narrower and deeper
- Heart-shaped inlet
- Narrow subpubic angle (<90°)
- Heavier bones
The female pelvis is wider and shallower for childbirth. Feature Female Male Inlet Oval / round Heart-shaped Subpubic angle Wide (>90°) Narrow (<90°) Cavity Shallow, wide Deep, narrow Applied
- Obstetric importance (pelvimetry)
🔑KEY POINTS TO REMEMBER- Female pelvis: wide, shallow, oval inlet, subpubic angle >90°.
- Male pelvis: narrow, deep, heart-shaped inlet, angle <90°.
- Obstetric relevance.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The anal canal is the terminal ~4 cm of the GI tract; the dentate (pectinate) line divides it into two developmentally distinct halves.
Above the Dentate Line
- Endodermal (hindgut)
- Columnar epithelium
- Visceral (autonomic) — painless
- Internal haemorrhoids
Below the Dentate Line
- Ectodermal
- Squamous epithelium
- Somatic (pudendal) — painful
- External haemorrhoids, fissures
The dentate line separates visceral (painless) from somatic (painful) anal canal. Feature Above line Below line Origin Endoderm Ectoderm Nerve Autonomic Somatic Pain No Yes Applied
- Internal (painless) vs external (painful) haemorrhoids
🔑KEY POINTS TO REMEMBER- Dentate line: endoderm above, ectoderm below.
- Above = visceral (painless); below = somatic (painful).
- Internal vs external haemorrhoids.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The uterus is supported by muscular and ligamentous structures that prevent prolapse.
Primary (Muscular) Support
- Pelvic diaphragm (levator ani) — most important
- Perineal body
- Urogenital diaphragm
Ligamentous Support
- Uterosacral ligaments
- Transverse cervical (cardinal / Mackenrodt) ligaments
- Pubocervical ligaments
- Round & broad ligaments (maintain position)
Muscular floor plus ligaments hold the uterus and prevent prolapse. Type Support Muscular Levator ani, perineal body Ligament Cardinal, uterosacral Applied
- Weakness → uterine prolapse
🔑KEY POINTS TO REMEMBER- Main support = pelvic diaphragm (levator ani).
- Ligaments: cardinal, uterosacral, pubocervical.
- Weakness → prolapse.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The prostate is a fibromuscular gland surrounding the male urethra at the bladder neck, contributing to seminal fluid.
Features
- About the size of a walnut
- Surrounds the prostatic urethra
- Five lobes (anterior, posterior, median, 2 lateral)
- Secretes alkaline seminal fluid
Zones (Clinical)
- Peripheral zone — site of cancer
- Transitional zone — site of BPH
The prostate hugs the urethra; BPH and cancer arise in different zones. Condition Zone BPH Transitional (central) Cancer Peripheral Applied
- BPH → urinary retention
- Cancer felt on PR (hard, irregular)
🔑KEY POINTS TO REMEMBER- Prostate surrounds the prostatic urethra at the bladder neck.
- BPH → transitional zone; cancer → peripheral zone.
- PR exam for cancer.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The perineal body is a fibromuscular node in the centre of the perineum where several muscles converge — a key support of the pelvic floor.
Location & Attachments
- Between the anal canal and the vagina / bulb of penis
- Converging muscles: levator ani, perineal muscles, external anal sphincter
Functions
- Central support of the perineum & pelvic floor
- Especially important in females
Several perineal muscles anchor to this central node, supporting the floor. Feature Detail Location Central perineum Role Pelvic floor support Applied
- Torn in childbirth → prolapse
- Protected by episiotomy
🔑KEY POINTS TO REMEMBER- Perineal body = central fibromuscular node.
- Muscles converge; supports the pelvic floor.
- Childbirth tear → prolapse.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The pudendal nerve (S2, S3, S4) is the main nerve of the perineum, supplying its muscles and skin.
Course
- From the sacral plexus (S2–S4)
- Exits via the greater sciatic foramen
- Re-enters via the lesser sciatic foramen
- Runs in the pudendal (Alcock’s) canal
Supplies
- External anal & urethral sphincters
- Perineal muscles
- Skin of the perineum & genitalia
The pudendal nerve runs in Alcock’s canal to supply the perineum and sphincters. Modality Supplies Motor Sphincters, perineal muscles Sensory Perineum, genitalia Applied
- Pudendal nerve block (childbirth)
- ‘S2, 3, 4 keep the pelvis off the floor’
🔑KEY POINTS TO REMEMBER- Pudendal nerve S2–S4; runs in Alcock’s canal.
- Supplies sphincters, perineal muscles, perineal skin.
- Blocked for childbirth analgesia.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.