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

T lymphocyte and B lymphocyte

T lymphocyte and B lymphocyte 

 T lymphocyte

T lymphocyte develop from bone marrow-derived cells that migrate to the thymus .

They are essential to human defense against infectious organisms and some cancers. There are two main types of T-cells: helper T-cells and killer T-cells. Helper T-cells stimulate B-cells to make antibodies and help killer cells develop. Killer T-cells directly kill cells that have already been infected by a foreign invader. T-cells also use cytokines as messenger molecules to send chemical instructions to the rest of the immune system to ramp up its response. Activating T-cells against cancer cells is the basis behind checkpoint inhibitors, a relatively new class of immunotherapy drugs that have recently been federally approved to treat lung cancer, melanoma and other difficult cancers. Cancer cells often evade patrolling T-cells by sending signals that make them seem harmless. Checkpoint inhibitors disrupt those signals and prompt the T-cells to attack the cancer cells.

B lymphocyte

B cells, also known as B lymphocytes, are a type of white blood cell of the lymphocyte subtype.

 They function in the humoral immunity component of the adaptive immune system by secreting antibodies.

Additionally, B cells present antigens (they are also classified as professional antigen-presenting cells (APCs)) and secrete cytokines

 In mammals, B cells mature in the bone marrow, which is at the core of most bones.

 In birds, B cells mature in the bursa of Fabricius, a lymphoid organ where they were first discovered by Chang and Glick, (B for bursa) and not from bone marrow as commonly believed.

B cells, unlike the other two classes of lymphocytes, T cells and natural killer cells, express B cell receptors (BCRs) on their cell membrane

 BCRs allow the B cell to bind to a specific antigen, against which it will initiate an antibody response

While both are critical to the body's defense against disease and infection, T-cells and B-cells play very different roles. CART therapy and checkpoint inhibitors are examples of how researchers are using what they’ve learned about T-cells specifically in developing new cancer treatments. But as their differences and similarities show, both types of immune cells employ important natural defenses in helping the body fight cancer.

 

 Summary of T Lymphocyte and B lymphocyte 

topic	T lymphocyte	B lymphocyte
Origin	Bone marrow	Bone marrow
Mature	Thymus	Bone marrow
Location of mature cell	Mature cell present within the lymph node	Mature cell present out side the lymph node
Receptors	Bear TCR receptors	Bear BCR receptor
Viral antigens	Recognized viral antigens on the outside of infected cells	Recognized  antigens on the surface of bacteria and viruses
Life span	Long	Short
Type of immunity	Cell mediated immunity	Humoral or Antibodies mediated immunity
Types of active cell	Cytotoxic T cell , Helper T cell and suppressor / regulatory T cells and memory cells	Plasma cell and memory cells
Surface antigens	Lack of surface antigen	Have surface antigen
Secrete	Lymphokines	Antibodies
%	80% are T lymphocyte	20% are B lymphocyte
Site of infection	Move to the site of infection	Does not move to the site of infection
Tumor cell	Act against tumor cell or transplant	Do not act against tumor cell or transplant
Effect on immune system	Inhibitory effect on immune system	No inhibitory effect on immune system
Functions	·         Lyse virus infected cells and cancer cells ·         Provides immunity against most viruses and few bacteria ·         Aid B cell in antibodies production ·         Modulate immune response	Help eliminate free foreign invaders by enhancing innate immune responses against them Provide immunity against most bacteria and few viruses