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Study of the microscopic structure of the human organism co
related with the development, function and clinical
significance.
It is derived from Greek term” anatome” meaning cutting apart.
EMBRYOLOGY
It is the study of the formation and development of the embryo
from the moment of its inception upto
the time when it is born
as an infant.
Gonads: no: of chromosomes in an organism=23 pairs/46 no.
♂-----44
autosomes –XY
♀----44
autosomes - XX
Karyotyping : Classification of chromosomes based upon their
differences that enable us to identify each chromosome
individually.
Spermatogenisis : The process of formation and development of
spermatazoan .
Formed in the wall of the
seminiferous tubules of testes.
Spermiogenesis (spermateleosis) : The process of transformation
of a circular spermatid to a spermatozoan.
Mature spermatozoan: Has a head, a neck middle piece and a
principal piece or tail. Head is covered with a cap called
acrosome.
Length -50-60 microns
Golgi apparatus forms the acrosomic cap.
Nucleus forms head.
Mitochondrion forms the sheath of middle piece.
Proximal centriole comes to lie in the neck.
Distal centriole becomes ring shaped and forms the annulus.
Axial filament grows out from the centriole and is present in
middle piece and tail.
Viability of spermatozoa =4 days.
Ovulation:
The shedding of ovum from the ovary.
Corpus luteum- It is an important structure derived after the
rupture of ovarian follicle to shed the ovum.
It secretes hormone progesterone.
Viability of ovum =24 hrs
Menstrual cycle: Divided into 4 phases
1.Post menstrual phase
2.Proliferative
3.Secretory(premenstrual)
4.Menstrual
Follicular phase ---post menstrual + proliferate phase -~
Oestrogen
Luteal phase – secretory +menstrual phase -~
progesterone
Size of Oocyte— 120u.
Approximate number of occytes at puberty—around 40,000.
Approximate number of ova liberated during reproductive period
of female—around 300 to 400.
Time required for formation of spermatozoa from spermatogonium—64
days.
Fertilized ovum reaches uterine cavity—by 4 days.
Implantation of ovum (fertilized) occurs—about 7th day.
Primitive uteroplacental circulation begins—by end of 2nd week.
Number of somites in embryo — 42 to 44.
Time of somite formation — 21 to 30th day.
Organogenesis — from 4th to 8th weeks.
Formation of primary ovary in a female takes place by 8th week
Differentiation of genital organs
1.Persons with two X chromosomes are female; those with one x
and one y are male.
2.Y chromosome bears a gene responsible for production of a
testis determining factor.
3.Interstitial cells in testis produce testosterone .It forms a
complex with certain receptor proteins which attaches itself
to
DNA. This causes the mesonephric duct to develop as in male.
4.Presence of dihydrotestosterone .
5.Sertoli cells produce mullerian inhibiting substance .This
causes regression of paramesonephric ducts.
Genital swellings in male differentiate into scrotum whereas in
a female, they form labia majora.
The mesonephric duct in a female develops into Gartner's duct.
The Mullerian ducts in male develop into appendix testes whereas
in a female, they develop into uterus and uterine tubes.
In female, the homologue of prostatic glands are paraurethral
glands.
FOETAL CIRCULATION
Differs from adult circulation in
a) Source of oxygenated blood is not
the lung but the placenta.
b) Oxygenated blood from placenta
comes to foetus through umbilical vein and joins the left branch
of portal vein.
Small portion passes through the substance of
the liver to I V, but the greater part passes direct to I V
through the ductus venosus.
Changes at birth: 1) umbilical artery contracts.
2) Lumen of umbilical veins and ductus venosus occludes and this
takes place a few minutes after birth.
3) Ductus arteriosus occludes by about 10 th day.
4) Pulmonary vessels increase in size.left atrial pressure rises
than that of right atrium and leads to closure of foramen ovale.
Remnant of
Umbilical artery -
medial umbilical ligament
Left umbilical vein -
ligament teres of the liver
Ductus venosus - Ligamentum venosum
Ductus arteriosus - Ligamentum arteriosum
OSTEOLOGY
Study of bones.
Bones are divided according to their
1)Position
Human skeleton -------axial} bones of skull, vertebral column,
ribs, sternum, hyoid.
-------appendicular}
bones of pectoral, pelvic girdle ,upper and lower limbs
2) Shape
Long bones: eg: Femur, tibia, humerus, ulna, radius, and fibula
Short long bones: eg: Metacarpals, metatarsals, phalanges
Short bones: eg: Carpals, tarsals
Flat bones: eg : Scapula , sternum, ribs, parietal and frontal.
Pneumatic bones : Maxillary ,sphenoid , ethmoid, mastoid part of
temporal bone.
Irregular bones: eg: Vertebrae, skull bones
Sesamoid bone: eg: patella, pisciform, fabella
2)Structure
Compact bone =consisting of haversian system
Cancellous (spongy) bone = consisting of irregularly placed
lamellae.
Diploic =consisting of inner and outer tables of compact bone
with intervening porous layer.
3)Development
Ecto chondral bones: which develop in membrane (membranous)
Endochondral bones: which develop in cartilage. (cartilageneous)
Total no of bones ---206
Upper limbs-64
Lower limbs-62
Vertebrae-33
Skull - 29(14-facial
bones
- 14- cranial
bones , hyoid bone )
Sternum-1
Ribs- 12 pairs
Longest bone---femur
Smallest bone---stapes
Strongest part in human body- Enamel of teeth
Largest sesamoid bone --- Patella developing in quadriceps.
Microscopic unit of a bone: Haversian system (secondary osteone)
Ossification
Process of gradual bone formation.
a)Ossification in membrane (direct)—easy process
Eg: clavicle, bones of face,vault of skull.
b)Ossification in cartilage (Indirect) ---gradual process.
Eg: bones of limbs, trunk.
Secondary cartilage bone: eg: neck of mandible, sternal end of
clavicle.
Primary centres of ossification may be single or multiple
,appear before birth between 6th – 8th week of foetal life
except cuneiform ,navicular bones .
Secondary centres of ossification are multiple and appear after
birth except lower end of femur.
Ossification of acetabulum is complete at 16-17 years
Growing ends of bones of upper limb—upper end of humerus &
Lower end of radius and
ulna
Growing ends of bones of lower limbs ---- lower end of femur &
Upper limbs of tibia and fibula
In long bones, growing ends fuse with shaft at 20 yrs and
opposite ends at about 18 yrs.
In other bones it is between 20-25 yrs.
Types of epiphysis are :
a) Pressure epiphyses - located at pressure points like joints
b) Traction epiphyses: subjected to traction by pull of
muscles when located at the muscular attachment
c) Atavistic epiphyses: centre appearing in the part of bone
which was orginally a separate bone in evolution eg : Coracoid
process of scapula.
Hyaline cartilage has a tendency to get calcified in later years
of life.
Skull bones—22
bones
Facial bones (14)-paired-nasal, maxillae, zygomatic, palantine,
lachrymal, inferior nasal connchae.
Unpaired-mandible, vomer
Cranial bones (14)-paired- parietal, temporal, ear ossicles
Unpaired- frontal, ethmoid, sphenoid, occipital.
Carpal bones- 8 bones Lat TO medial (Proximal) Scaphoid, lunate,
triquetral, pisiform
(Distal)—Trapezium,
trapezoid, capitate, hamate.
Tarsal bones-7 bones (proximal) Talus, calcaneus
(distal) medial cuneiform, intermediate cuneiform, lateral
cuneiform, cuboid.
Largest and strongest of tarsal bones—Calcaneus
Paranasal sinuses
4 pairs : Frontal, sphenoidal, ethmoidal, maxillary.
Largest of all air sinuses ---Maxillary sinus (Antrum of
Highmore)
Foramina of skull
Anterior cranial fossa :
1.Foramen caecum: lies between the alae of crista galli of
ethmoid and frontal crest. Transmits an emissary vein.
Middle cranial fossa:
2.Optic canal (foramen): Transmits optic nerve, opthalmic
artery.
3.Superior orbital fissure: Bounded by lesser wing above,
greater wing below and body of sphenoid medially.
Divided by three compartments by common tendinous ring.
Transmits
–superior and inferior divisions of oculomotor, nasociliary
nerve, abducent nerve, trochlear nerve, frontal nerve,
lacrimal
nerve, lachrimal artery, orbital branch of middle meningeal
artery, superior ophthalmic vein,recurrent meningeal
branch of
lachrymal artery, inferior ophthalmic vein.
4.Foramen rotundum---transmits maxillary nerve.
5. Foramen ovale --- transmits mandibular nerve,accessory
meningeal artery ,lesser superficial petrosal nerve, emissary
vein.
6. Foramen spinosum--- transmits middle meningeal artery, nervus
spinosus
7. Foramen lacerum--- transmits Internal carotid artery.
8. Carotid canal---- transmits internal carotid artery with
plexus,
emissary veins, meningeal lymphatics.
Posterior cranial fossa:
9. Jugular foramen --- transmits 9th,, 10, 11th cranial nerves.
10. Foramen magnum---largest foramen in skull.
Divided into anterior small
compartment: Apical ligament
Upper band of cruciate ligament
Condylar parts on sides.
Posterior large compartment: lower end of medulla oblongata, 2
anterior and one posterior spinal artery, veins joining
venous plexus, lower part of tonsil of cerebellum, vertebral
artery, sympathetic plexus, spinal root of accessory nerve.
Ribs:
12 in number on each side.
True ribs—1-7th
False ribs--- 8-12th
Floating ribs --- 11-12th
Atypical ribs—1, 2, and 10.11, 12th.
Folds of duramater
Falx cerebri – encloses superior
sagittal sinus, inferior sagittal sinus, straight sinus
Tentorium cerebelli- encloses
transverse sinuses, posterior petrosal sinuses.
Falx cerebelli—encloses occipital
sinus
Diaphragma sellae—encloses
anterior and posterior intercavernous sinuses.
Important points in skull
1.Bregma: meeting of coronal and sagittal sutures.site of
anterior fontanelle, closes at 11/2 yrs of age.
2 .Lambda: meeting of sagittal and lambdoid sutures .site of
posterior fontanelle ,closes at 2-3 months of age.
3. Nasion : meeting point of internasal and fronto nasal
sutures.
4. Inion : centre of external occipital protruberance.
5. Pterion : area formed by meeting of frontal, squamous part of
temporal ,parietal, greater wing of sphenoid.deep to
this lies
anterior branch of middle meningeal artery, middle meningeal
vein ,stem of the lateral sulcus.
6. Asterion : point at the postero inferior angle of parietal
bones.
Diaphragm
Inferior aperture (outlet )of thorax.
Aortic opening—T12- transmits Aorta, thoracic duct, Azygos vein
Oesophageal opening—T10-transmits oesophagus, gastric nerves,
oesophageal branches of left gastic artery.
Venecaval opening --- T8 transmits inferior venecava, branches
of right phrenic nerve.
CEREBROSPINAL
FLUID (CSF)
Definition
CSF is a modified tissue fluid in the central nervous system. It
is contained in the ventricular system of brain and the
subarad
space of brain and spinal cord. CSF replaces lymph in the CNS.
It acts as a sensitive mirror which reflects
diseases of the na
system. Formation
1.The bulk of the CSF is formed by choroid plexuses of the
lateral ventricules, and the lesser amounts by the choroid
plexus
the third and fourth ventricles. '
2.Possibly it is also formed by the capillaries on the surface
of the brain and spinal cord.
Circulation
CSF passes from the lateral ventricles to the third ventricle
through foramina of Monro (interventricular foramina). From
ventricle it passes to the fourth ventricle through cerebral
aqueduct. From fourth ventricle the CSF passes to the
subarachnoid
around the brain and spinal cord through the
foramen of Magendie and foramina of Luschka.
Absorption
1.CSF is absorbed chiefly by the arachnoid villi and
granulations, and is thus drained to the cranial venous sinuses.
2.It is also absorbed partly by the perineural lymphatics around
I, II, VII and VIII cranial nerves
3.And also by the veins related to the spinal nerves.
Rate of Formation
200 cc/hour, 5000 cc/day.
Total Quantity About 150 cc. Pressure:60-150 mm of
fluid (or water). Composition
Proteins 20-40 mg per 100 cc.
Sugar 50-75 mg per 100 cc.
Chlorides 720-750 mg per 100 cc.
Cells 0-5 per cubic mm
Functions
It is (a) protective, (b) nutritive, and (c) excretory to the
CNS.
Applied Anatomy
1.CSF can be obtained by (a) lumbar puncture, (b) cisternal
puncture, or (e) ventricular puncture. Lumbar puncture is 1st
method of all and is commonly used. It is done in the interspace
between third and fourth lumbar spines.
2.Biochemical analysis of the CSF is of diagnostic value, as the
cases of meningitis and spinal tumours.
3.Drainage of CSF at regular intervals is of therapeutic value
in meningitis. Certain intractable headaches of unknown are
also known having been caused by a mere lumbar puncture with
drainage of CSF.
4.Obstruction to the flow of CSF in the ventricular system of
brain leads to hydrocephalus in children .Spinal obstruction
leads to Froins syndrome.
Length
of parotid duct: 5 cm.
Length of submandibular duct: 5 cm.
Length of auditory tube: 36 mm.
Bony part: 12 mm.
Cartilagenous part: 24 mm
Length of external acoustic meatus(from bottom of choncha):
2.4 cm.
Bony part:16 mm.
Cartilagenous part:8 mm.
Transverse diameter of mid cavity
Opposite the centre of tympanic membrane: 2 mm.
Total number of cones in the retina: 6.3 to 6.8 million.
Length of pharynx: 12 to 14 cm
Length of larynx
Length of vocal cords
Length of Trachea -
Pituitary gland: 13 x 8 mm.
Heart — Measures 12 x 9 cm (5x3 or 3.5
inches)
Weight 300 g (males)
250 g (females)
Termination of oesophagus 11th Thoracic vertebra.
Constrictions in oesophagus
:
·
at commencement 15 cm from incisor teeth.
·
at crossing over by aortic arch 22.5 cm from incisor teeth.
·
at crossing over by left principal bronchus 27.5 cm from incisor
teeth.
·
at its point of piercing diaphragm 40 cm from incisor teeth.
Stomach :
·
Cardiac orifice — Behind left 7th costal cartilage 1" from its
junction with sternum.
·
Pyloric orifice — 1.2 cm (0.5") to the right of midline on
transpyloric plane.
·
Capacity — at birth 30 ml; adults 1500 ml.
Length of small intestine: 6 to7 metres
Length of duodenum: 10” or 25 cm
1 st part: 5 cm
2nd part: 7.5 cm
3rd part: 10 cm
4th part: 2.5 cm
Length of large gut: 1.5 metres
Anal canal
Hilum of kidney — Transpyloric plane (LI).
Kidney:Length:
11 cm, Breadth : 6 cm, Antero-posterior diameter: 3 cm
Length of Ureter : 25 cm
Length of male urethra: 18-20 cm
Spermatic cord : 9-10 cm
Length of inguinal canal: 4 cm
Testis: Length-4.5 cm, Breadth-2.5cm, Anteroposterior dr-3
Ovary: Length -3 cm, Width-1.5 cm,Thickness-1 cm
Uterus:
Length-7.5 cm, Breadth-5 cm,Antero-posterior diameter-2.5 cm
Weight :30 to 40 gms
Uterine tubes:
Length-10 cm
Saphenous opening — Height 1.5 to 8 cm; Width 1 to 3 cm
Femoral sheath — Length 3 to 4 cm.
Femoral canal — Length 1.25 cm.
Tendo calcaneus — Length 15 cm.
Weight of spinal cord
— 30 gms.
Length of spinal cord — 45 cm.
Filum terminale — 20 cm.
Internum —15 cm.
Externum — 5 cm.
Commencement of spinal cord — Cranial border of C1 vertebra
(Atlas).
Termination of spinal cord -— lower border of LI or disc between
LI & L2 vertebrae.
Cervical enlargement of spinal cord — Circumference 39 mm.
Extends from LI to SI spinal segments.
Lumbar enlargement of spinal cord — Circumference 35 mm. Extends
from LI to S3 spinal segments.
Vertebral levels of spinal segments
Cervical vertebral spine corresponds to succeeding cord segment
Eg : C6 spine to C7 segment.
Upper thoracic spine corresponds to two spinal segments lower Eg
: T4 spine corresponds to T4 spinal segments.
Lower thoracic spine corresponds to three spinal sements below
Eg : T10 spine to LI spinal segment. T11 spine to
L3segment,
T12 spine to SI segment.
New born child lower limit of spinal cord is at — L3 vertebral
upper border.
Length of medulla oblongata — 3 cm.
Shortest segment of brain stem — mid brain 2.cm.
Thalamus-Length —- 4 cm.
Corpus callosum length 10 cm.
Specific gravity of C.S.F: 1007.
Pressure of CSF (in recumbent position):100 to 150 mm of H2O
Total volume of CSF in man: 140 ml; amount of CSF in Ventricles
25 ml.
Commencement of subclavian artery — Behind sternoclavicular
joint.
Termination of Subclavian artery — Outer border of 1st rib.
Termination of Brachial artery — Neck of radius.
Thoracic Aorta :
Commencement — T4 Vertebral lower border.
Termination — T12 Vertebral body.
Abdominal Aorta commencement — T12 Vertebral body.
Coeliac Trunk:Origin
— T12, Length —1.25 cm.Superior mesenteric artery — LI.
Inferior mesenteric artery —L3.
Commencement of common iliac —L4 vertebral body.
Bifurcation of common iliac—Sacroiliac joint
External iliac termination —Mid-inguinal point.
Vertebral prominence — C7.
Superior angle of scapula —T2.
Upper border of manubrium sterni (suprasternal notch)—T2, T3
vertebral junction.
Spine of scapula —T3
Sternal angle
—T4 & T5 (Disc between).
Inferior angle of scapula — T7.
Xiphisternal joint — T9.
Tonsil is derived from 2nd pouch
CSF to plasma glucose ratio is normally 0.6 to 0.8
Appearance of permanent kidney — 5th week of Intrauterine
period.
Invasion of primordial germ cells into developing gonad — 5th
week.
Appearance of neural plate (nervous system) — 3rd week.
Development of eye — between 4th and 7th weeks.
Appearance of limb buds — beginning of 5th week.
Descent of testis:
At deep inguinal ring— 7th month of intra uterine life.
In inguinal canal — 8th month of intrauterine life.
At superficial inguinal ring — 9th month of intrauterine life.
Haller's circle is found in the Pyloric orifice.
Marginal artery of Sudeck lies at 2.5-3.8 cm from colon.
Portal vein is about 8 cm long.
The maximum breadth of mesentry is in central part and is 8
inches
The lesser omentum is a fold of peritoneum extending from lesser
curvature of stomach and first 2 cm of duodenum to the liver.
Common carotid artery is derived from III aortic arch.
At full term, diameter of placenta is 6-8 inches.
Mesentry
contains about 100-200 lymph nodes.
Between lowest sigmoid and sup. Rectal artery anastomosis is
regarded as the critical point of Sudeck.
Mesentry is fan shaped fold of peritoneum.
Total area of placenta is 14 sq. m.
Oesophagus structure is related to both left and right lung.
Weight of parathyroid gland is 50 mg.
Length of caecum is 6 cm.
Sprain of ankle is most often due to abduction.
The superficial muscles of the back of leg are supplied by S1,2.
Thickness of suprarenal is 10 mm.
Duodenojejunal is largest duodenal recess.
Cisterna chyli is 5-7 cm long.
Ovary has minimum thickness.
V pharyngeal arch disappears at the earliest.
Weight of prostate gland is 8 gm.
Longest part of duodenum is III.
Left dome of diaphragm corresponds to the lowest part of 5 rib.
Width of stomach is 10-12 cm.
Claustrum is situated between putamen and Insula
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