Summary of Closure of frontanelle : human skull of children

Summary of Closure of frontanelle
In humans, the sequence of fontanelle closure is as follows
The posterior fontanelle generally closes 2 to 3 months after birth;
The sphenoidal fontanelle is the next to close around 6 months after birth
The mastoid fontanelle closes next from 6 to 18 months after birth; and
The anterior fontanelle is generally the last to close between 12 to 18 months.

Lecture notes of frontanelle of human skull of children

Frontanelle :  

Definition :

A fontanelle is an anatomical feature of the infant human skull. They are soft membranous gaps between the cranial bones.

Clinical importance of frontanelle: 

1. The fontanelle allows the skull to deform during birth to ease its passage through the birth canal 

2. and for expansion of the brain after birth.

3. A sunken fontanelle indicates dehydration 

4. whereas a very tense or bulging anterior fontanelle indicates raised intracranial pressure

 

Number of frontanalle in human skull of children : 4 

1. anterior frontanelle 
2. Posterior frontanelle 
3. sphenoidal frontanelle 
4. mastoid frontanelle

Anterior frontanelle: 

Anterior superior angle of parietal bone forms bregma in children it is called anterior frontanelle The anterior fontanelle bregmatic fontanelle, frontal fontanelle is the largest fontanelle, and is placed at the junction of the sagittal suture, coronal suture, and frontal suture;
It is lozenge shaped, and measures about 4 cm in its antero posterior and 2.5 cm in its transverse diameter.
The anterior fontanelle typically closes between the ages of 12 and 18 months.

Posterior frontanelle :
Posterior superior angle forms Lambda in children it is called posterior fontanelle
The posterior fontanelle lambdoid fontanelle, occipital fontanelle is a gap between bones in the human skull known as fontanelle, triangular in form and situated at the junction of the sagittal suture and  lambdoidal suture.
It generally closes in 6 to 8 weeks from birth.
A delay in closure is associated with congenital hypothyroidism.
Premature complete ossification of the sutures is called craniosynostosis.

Sphenoidal frontanelle:
Anterior inferior angle of parietal bone forms pterion in children it is called sphenoidal frontanelle
This angle is internally marked by groove for anterior division of middle meningeal artery
What is pterion
Ans union between 4 bones
Frontal bone
Anterior inferior angle of parietal bone
Greater wing of sphenoid
Squamous part of temporal bone
What is the importance of pterion
Internal surface of pterion is lodged by anterior division of middle meningeal artery 

Mastoid frontanelle :
Posterior inferior angle of parietal bone forms asterion in children it is called mastoid frontanelle
Internally a groove is present which lodges sigmoid sinus
Summary of Closure of frontanelle
In humans, the sequence of fontanelle closure is as follows
The posterior fontanelle generally closes 2 to 3 months after birth;
The sphenoidal fontanelle is the next to close around 6 months after birth
The mastoid fontanelle closes next from 6 to 18 months after birth; and
The anterior fontanelle is generally the last to close between 12 to 18 months.

Lecture notes of parietal bone

Parietal bone

Anatomical points

Superior border is longest, thickest and serrated

Superior border lies in median plane
External surface is convex

Anterior inferior angle is acute and internally marked by groove for anterior division of middle meningeal vessel

Morphological type of bone flat bone

 

Structure of bone : inner and outer table: compact bone and middle diploe spongy bone 

ossification intra membranous ossification 

Development paraxial mesoderm 

Parts of parietal bone

 external and internal surface , four borders : anterior , inferior , posterior and superior , four angle anterior superior , anterior inferior , posterior superior and posterior inferior

superior border longest, thickest and serrated and
internally marked by a sulcus known as sagittal sulcus
which lodges superior sagittal sinus
superior border is articulated with opposite parietal bone formed sagittal suture
Granular pit present side of sagittal sulcus which lodge arachnoid granulation
Anterior border is straight and serrated and articulated with frontal bone formed coronal suture

Posterior border is straight and serrated and articulated with occipital bone formed lambdoid suture

 
inferior border irregular and serrated and internally marked by posterior division of middle meningeal artery at the middle of inferior border
Inferior border is articulated with 3 bones
from antero posteriorly
Greater wing of sphenoid bone
Squamous part of temporal bone
mastoid part of temporal bone .
Anterior superior angle of parietal bone forms bregma in children it is called anterior frontanelle

A fontanelle is an anatomical feature of the infant human skull. They are soft membranous gaps between the cranial bones.
The fontanelle allows the skull to deform during birth to ease its passage through the birth canal and for expansion of the brain after birth.
A sunken fontanelle indicates dehydration 
whereas a very tense or bulging anterior fontanelle indicates raised intracranial pressure

The anterior fontanelle bregmatic fontanelle, frontal fontanelle is the largest fontanelle, and is placed at the junction of the sagittal suture, coronal suture, and frontal suture;
It is lozenge shaped, and measures about 4 cm in its antero posterior and 2.5 cm in its transverse diameter.
The anterior fontanelle typically closes between the ages of 12 and 18 months.
Posterior superior angle forms Lambda in children it is called posterior fontanelle
The posterior fontanelle lambdoid fontanelle, occipital fontanelle is a gap between bones in the human skull known as fontanelle, triangular in form and situated at the junction of the sagittal suture and  lambdoidal suture.
It generally closes in 6 to 8 weeks from birth.
A delay in closure is associated with congenital hypothyroidism.
Premature complete ossification of the sutures is called craniosynostosis.
Anterior inferior angle of parietal bone forms pterion in children it is called sphenoidal frontanelle
This angle is internally marked by groove for anterior division of middle meningeal artery
What is pterion
Ans union between 4 bones
Frontal bone
Anterior inferior angle of parietal bone
Greater wing of sphenoid
Squamous part of temporal bone
What is the importance of pterion
Internal surface of pterion is lodged by anterior division of middle meningeal artery
Posterior inferior angle of parietal bone forms asterion in children it is called mastoid frontanelle
Internally a groove is present which lodges sigmoid sinus
Summary of Closure of frontanelle
In humans, the sequence of fontanelle closure is as follows
The posterior fontanelle generally closes 2 to 3 months after birth;
The sphenoidal fontanelle is the next to close around 6 months after birth
The mastoid fontanelle closes next from 6 to 18 months after birth; and
The anterior fontanelle is generally the last to close between 12 to 18 months.
external Surface of parietal bone
Superior temporal line : gives attachment to the temporal fascia and lateral part of epicranial aponeurosis . Above the superior temporal line the bone is covered by the epicranial aponeurosis
inferior temporal line & the area of bone below it form the major part of temporal fossa & provide origin to the temporalis muscle
parietal foramen It is located close to the posterior part of superior border of external surface which transmits an emissary vein connecting the superior sagittal sinus with the veins of the scalp and a meningeal branch from the occipital artery

The external surface of the parietal bone is convex, smooth, and marked near the center by an eminence, the parietal eminence 
parietal tuber
Importance of  parietal eminence 
It indicates the point where ossification commenced
The maximum transverse diameter of skull measures by these points
It acts as a reference point for surface anatomy
Beneath the parietal tuber, the posterior ramus of lateral sulcus of the brain terminates with an upturned end
Opposite the parietal tuber supramarginal gyrus the Wernickes sensory speech area is located
internal surfaces of parietal bone is deeply concave , faces downward and medially
impression of sulci and gyri of cerebrum
impression of anterior division of middle meningeal artery at internal surface of anterior inferior angle
impression of posterior division of middle meningeal artery at middle of inferior border :sagittal sulcus near the superior border which lodge superior sagittal sinus

The margin of superior sagittal sulcus provide attachment to the dural folds the falx cerebri
Granular pits are present near the sagittal sulcus for lodgement of arachnoid granulations through which cerebrospinal fluid is absorbed in the superior sagittal sinus
sulcus for sigmoid sinus is present near the posterior inferior angle
Parietal bone overlaps partially all four major lobes of cerebral hemisphere.
central sulcus
postcentral gyrus
precentral gyrus
intraparietal sulcus
superior parietal lobule
lateral sulcus
supramarginal gyrus
angular gyrus
superior temporal gyrus

The following functional areas of brain are covered by parietal bone
Motor and somesthetic sensory area
Broca’s motor speech area
Wernicke’s sensory speech area
Primary and secondary auditory area
Two imaginary lines may be drawn on the internal surface of parietal bone
A line extends downward and forward from the superior border about 3 to 4 cm behind the anterior superior angle for a distance of about 7.5 cm .It is corresponds with the central sulcus and separates the frontal lobe of the brain in front from the parietal lobe behind
Two imaginary lines may be drawn on the internal surface of parietal bone
2. Another line extending from the anterior inferior angle to the inner aspect of parietal tuber coincides with the posterior ramus of lateral sulcus and intervenes between the frontoparietal lobes above and in front and the occipitotemporal lobes below and behind

 

Summary of Turner’s syndrome

 

Turner’s syndrome

Definition:

This syndrome is caused by the lack of sex chromosome (XO instead of XX).

Genetic disorder

It is a numerical genetic disorder also call monosomy

Genotype

Monosomy of sex chromosome (2n-1), here only one X chromosome, is present in females.

Chromosomal complement in somatic cell

45X0

Phenotype

Affected individuals are phenotypically female

Occurrence

1 in 2500 phenotypic females.

Symptome

Lymphedema, underweight and swelling or thickness of the neck.they have  underdeveloped breasts, uterus, vulva or vagina,but ovaries are not developed, so primary amenorrhea occurs, associated dysfunctions are hearing impairment, cardiovascular dysfunctions, shield chest with pin-point nipples, low set ear, bilateral cubital valgus, coarctation of aorta, and other congenital anomalies. 

Stature

Short stature

Gonadal sex

Are absent

Cause

Turner syndrome is not related to advanced maternal age; and in fact, is more likely due to instability of the Y chromosome leading to its loss during male meiosis since 75–80% of X chromosomes in TS patients are maternal in origin.

Cause of genetic disorder

Nondisjunction, anaphase lag

Barr body

Female  but barr body is absent due to absence of one  X chromosome

Treatment

There is no cure for Turner syndrome. It is commonly treated with replacement therapy including estrogen and growth hormones.

Gonad

Ovaries are not developed

 

Summary of Klinfelter’s syndrome

 

Klinfelter’s  syndrome

Definition: This syndrome is caused by the presence of an extra sex chromosome (XXY instead of XY)

Genetic disorder :

It is a numerical genetic disorder also call trisomy

Genotype

The trisomy of sex chromosome (2n+1), here one extra X chromosome- XXY, are present in males.

Chromosomal complement in somatic cell

47XXY

Phenotype:

. Affected individuals are phenotypically male

Occurrence

1 in 1100 phenotypic males.

Symptoms 

1.     Enlarged breasts, undeveloped penis and testicles associated azoospermia and sterility

2.     Length of legs and arms are usually longer than normal

3.     Increase gonadotropin levels

4.     Reduction of chest hair, axillary and pubic hair

Cause

Advance maternal age

Cause of genetic disorder

Nondisjunction

Barr body

Male but barr body is present due to presence of extra X chromosome

Treatment

Fertility treatment.

Psychological counselling.

Removal of excess breast tissue.

Hormonal Replacement Therapy.

Support and Educational evaluation.

Gonad

Testes absent or less developed

Stature : long 

 

 

Summary of endosteum

Summary of Endosteum:

Definition :

The endosteum (plural endostea) is a thin vascular membrane of connective tissue that lines the inner surface of the bony tissue that forms the medullary cavity of long bones.

Iit also lines the Haversian canal and all the internal cavities of the bone.

This endosteal surface is usually resorbed during long periods of malnutrition, resulting in less cortical thickness.

The outer surface of a bone is lined by a thin layer of connective tissue that is very similar in morphology and function to endosteum. It is called the periosteum, or the periosteal surface. During bone growth, the width of the bone increases as osteoblasts lay new bone tissue at the periosteum.

 To prevent the bone from becoming unnecessarily thick, osteoclasts resorb the bone from the endosteal side.

Composition of endosteum:

The endosteum consists of a layer of flattened osteoprogenitor cells and a type-III collagenous fibers (reticular fibers).

 

 The endosteum is noticeably thinner than the periosteum.

Classification of endosteum:

 it  is classified into three types based on their site: (i) Cortical endosteum: endosteum lining the bone marrow cavity, (ii) Osteon endosteum: Endosteum lining the osteons mainly contains nerves and blood vessels. (iii) Trabecular endosteum: Lines the trabecula near the developing part of the bone. It plays a role in the growth and development of the bone.

Functions:

Endosteum plays a role in the formation of an internal matrix by absorption and deposition of tissue.

The endosteum stimulates the uninterrupted internal bone resorption. The medullary canal, along with the overall bone diameter, increases because of endosteum-stimulated resorption.

Endosteal endoblasts secrete bone matrix and compose ridges beside the periosteal blood vessels. The bony ridges expand and fuse to convert the groove into a vascularized tunnel.

 Endosteal osteoblasts compose new lamellae and form new osteons. Finally, a new circumferential lamella appears beneath the periosteum. This process repeats for continuous bone diameter enlargement, which slows down with adulthood

Bone modeling and remodeling: Periosteum, endosteum, and its cells play a critical role in modeling and remodeling. 

Bone modeling and remodeling: Periosteum, endosteum, and its cells play a critical role in modeling and remodeling. 

• Bone remodeling is a process where osteoclasts and osteoblasts work sequentially to reshape and renew bone; the process continues throughout life. It divides into four phases; (a) recruitment and activation of osteoclasts, (b) resorption of old bony tissue, (c) apoptosis of osteoclasts, and activation of osteoblasts (d) laying of new organic matrix and mineralization.
• Bone modeling is a process to shape the bone during growth, development, and healing. Mechanical factors like stress, strain, tension, muscular attachment, etc. play an important role in bone modeling. Osteoblasts and osteoclast play an independent role in bone modeling.

 

Myoid cells of seminiferous tubules

Myoid cells of seminiferous tubules 

 

 

Definition : A peritubular myoid (PTM) cell is one of the smooth muscle cells which surround the seminiferous tubules in the testis

Ultrastructure: Myoid cells have a basal lamina and large numbers of actin filaments.

They also exhibit a significant amount of rough endoplasmic reticulum (rER), a feature indicating their role in collagen synthesis in the absence of typical fibroblasts.

Features:

1.     PTM cells are derived from mesonephric cells

2.     PTM cells are spindle shaped and

3.     They  form several thin elongated layers, approximately 5-7 cell layers, and surround Sertoli cells.

4.     Blood vessels and extensive lymphatic vasculature as well as Leydig cells are present external to the myoid layer.

5.     These are detected in the lamina propria of the seminiferous tubule and immunohistochemical studies have shown functional distinctions between these layers. The inner layers have been shown to express desmin, a smooth muscle phenotype, whereas the outer layers express vimentin, a connective tissue phenotype

Functions of myoid cells:  

1.     Rhythmic contractions of the myoid cells create peristaltic waves that help move spermatozoa and testicular fluid through the seminiferous tubules to the excurrent duct system.

2.     Peritubular myoid cells play a crucial role in the self-renewal and maintenance of the spermatogonial stem cell (SSC) population