Histology of Pineal body : easy and brief descriptions

Histology of Pineal body

The pineal body is a projection of the roof of the diencephalon. It is located in the brain above the superior colliculi.

Development : it is developed from neuroectoderm 

Histologically it has following parts

a)      Capsule : it is derived from pia mater . pia mater is thin collagenous connective tissue .

Septa(trabeculae)  arises from capsule divide the gland into incomplete lobules. The blood vessels and nerve  travel in the trabeculae to be distributed throughout the pineal body , providing it with rich vascular supply

b)     Parenchymal cells :

1.      Pinealocytes  : it is larger than neuroglial cells contain large, pale nuclei with prominent nuclei

Histology of vagina

Histology of vagina

The vagina is a fibromuscular tube that joins internal reproductive organs to the external environment . it extends from cervix of uterus to vestibule- the area between two labia minora . i

In a vargin the opening of vagina is surrounded by hymen – folds of muscous membrane, it is the remnant which derived from endodermal membrane

and it is the organ of copulation , it passage fetus during labour .

Histologically it has three  layers from inside to outside.

1.      Mucosa :

a)      Lining epithelium : non-keratinized stratified squamous epithelium. Keratohyaline granules may be present in the epithelial cells

b)     Lamina propria : this layer composed of fibro-elastic connective tissue

which contain numerous blood vessels , it is the unique feature of vagina .

Vagina has no muscularis mucosa and submucosa

2.      Muscle layer : organized into two indistinct layers : outer longitudinal and inner circular . the outer longitudinal layer continuous with the corresponding layer of the uterus and much thicker than the inner layer . bulbospongiosus the skeletal muscle is present near the opening of vagina.

3.      Adventitia : it has two layers 

Histology of thyroid gland with brief description of Thyroid follicle

Thyroid follicle

It is the structural unit of thyroid gland

Difference between follicular cells and para-follicular cells

Histologically Thyroid gland has following parts

1.      Capsule

2.      Parenchyma (glandular portion )

3.      Stroma  (supporting structure : connective tissue )

Parenchyma (glandular portion )

Glandular portion is formed by two types of cells

1.      Follicular cells

2.      Parafollicular cells

These two types of cells formed a definite structure known as thyroid follicle

Parts of thyroid follicle

It is a round structure contain a lumen and wall of thyroid follicle is lined by follicular cells and its basement membrane, so follicular cells are facing toward the follicular lumen.

Some whitish or pale colour bubbles are observed near the apical region of follicular cells , what is this ?

They are secretory vesicle which contain secretion of follicular cells and come out from the follicular cell into colloid by the process of exocytosis

        Again secretion of the colloid enter into the follicular cell by the process of endocytosis.   

Parafollicular cells are present peripheral part of follicular wall but within the basement membrane and it never exposed to lumen of thyroid follicle

Para-follicular cells of thyroid gland

Para-follicular cells of thyroid gland 

Topics	Para-follicular cells
Secretion	Calcitonin
Shape and size of cell	It is larger than the follicular cell and the shape of the cell is Round
Staining	It takes less staining
Exposure to luminal surface	It is never exposed to luminal surface, it is located peripheral part of thyroid follicle
Nuclei	It contain large pale stain nuclei
Golgi complex	Large amount of  golgi complex are present but  no definite location
Secretory vesicles	It contains numerous secretory vesicle present though out of the cell
rER	Present in small amount  but no definite location
Lysosome	Present but not abundant
Endocytotic vesicles or colloidal resorption droplets	No present
Microvilli	Absent
Development	4th pharyngeal pouch
Derived from	Neural crest