Platelets are cell fragments produced by megakaryocytes in the bone marrow that help the body form blood clots to stop bleeding. They have no nucleus and an average lifespan of 8-9 days. Platelets attach to damaged blood vessel walls and release chemicals that attract more platelets to form a hemostatic plug to stop bleeding. Low platelet counts can cause excessive bleeding while high counts have few symptoms. Platelet counts are regulated by thrombopoietin and can be affected by disease, medications, and lifestyle factors.

2.  platelets = small plate; thrombo=clot; cytes =
cells
 Platelet are smalllest blood cells, colourless,
nonnucleated, round or oval, flattened, disk-
shaped structures
 Cytoplasm =Golgi apparatus , endoplamic
reticulum, few mitochondria, microvsicles,
glycogen, lysosomes

4.  Platelets, also called thrombocytes (thromb- + -cyte,
"blood clot cell")Platelets are produced in the bone
marrow.
 Platelets are produced from very large bone marrow cells
called megakaryocytes.
 As megakaryocytes develop into giant cells, that results in
the release of over 1,000 to 3000 platelets per
megakaryocyte.
 Platelets have no cell nucleus.
 2–3 µm in greatest diameter.
 Megakaryocyte and platelet production is regulated by
thrombopoietin, a hormone in the kidneys and liver.

5.  Each megakaryocyte produces between
1,000 and 3,000 platelets during its lifetime.
 An average of 1011 platelets are produced
daily in a healthy adult.
 average life span of circulating platelets is 8
to 9 days
 In adults 1.5 -4 lakhs/mm3 of blood.

6.  On a stained blood smear, platelets appear as dark purple
spots.
 First, platelets attach to substances outside endothelium
 Second, they change shape, turn on receptors and secrete
chemical messengers
 Third, they connect to each other through receptor bridges.
 platelet granules. Alpha granules contain clotting mediators such
as factor V, factor VIII, fibrinogen, fibronectin, platelet-derived
growth factor, and chemotactic agents. Delta granules, or dense
bodies, contain ADP, calcium, serotonin, which are platelet-
activating mediators. -
 Platelets have d-granules that contain serotonin, adenosine
diphosphate (ADP), and Ca2


7.  The main function of platelets is to contribute to hemostasis: the
process of stopping (arrest) bleeding endothelium
 Phagocytosis of small particles (carbon)and (viruses)
organisms.
 Storage and transport (Serotonin )of chmicals. (Heparin)
 platelet provided factor 3 (platelet phospholipids ) process of
clotting blood.
 Serotonin released by platelet observed immediately after
vascular injury.
 Hemostatic plug is formed by platelet and is their primary
function.(stops bleeding).
 Platelet have growth factor repair of the damaged vassel wall.

8.  Platelet activation causes its membrane surface
to become negatively charged that negatively
charged phospholipids from the inner to the
outer platelet membrane surface.
 These phospholipids then bind the tenase and
prothrombinase complexes, two of the sites of
interplay between platelets and the coagulation.
 Calcium ions are essential for the binding of
these coagulation factors.

9.  Symptoms of a Low Platelet Count
 red, purple
 a rash with small red or purple dots
 nosebleeds
 bleeding gums
 bleeding from wounds that lasts for a prolonged period or
doesn’t stop.
 heavy menstrual bleeding
 blood in the stools or Gastrointestinal bleeding
 blood in the urine
 In more serious cases
 blood in the urine
 blood in the stool
 bloody or very dark vomit

10.  Increased Numbers Of Platelets
thaThrombocytosis
 Decreased Numbers Of Platelets
Thrombocytopenia

11.  aplastic anemia
 a vitamin B-12 deficiency
 an iron deficiency
 viral infections, including HIV, Epstein-Barr virus, and
chickenpox
 exposure to chemotherapy, radiation, or toxic chemicals
 consuming too much alcohol or Alcohol toxicity, ethanol abuse
 Leukemia
 an autoimmune disorder
 Pregnancy
 Viral, bacterial, and rickettsial infections
 Antiplatelet antibodies

12.  Idiopathic thrombocytopenia (ITP), also known as immune
thrombocytopenic is the result of antibody production
against platelets.
 Viral infections such as mononucleosis, hepatitis, HIV or
measles
 Heparin-induced thrombocytopenia (HIT) results in low
platelets when a person who is on or received heparin
therapy develops an antibody.
 Leukemia, lymphoma, or another cancer that has spread
(metastasized) to the bone marrow—people with cancers
after significantly decreased number of platelets.
 Aplastic anemia—a condition in which the production of all
blood cells is significantly reduced
 Long-term bleeding problems (e.g., chronic bleeding from
stomach ulcers)
 Sepsis, especially that caused by a serious bacterial
infection with Gram-negative bacteria.

13.  Cancer, most commonly lung, gastrointestinal, ovarian, breast or lymphoma
 Anemia, in particular iron-deficiency anemia and hemolytic anemia
 Inflammatory conditions such as inflammatory bowel disease (IBD) or
rheumatoid arthritis
 Infectious diseases such as tuberculosis
 Recovery from significant blood loss such as from trauma or major surgery
 After physical activity or exertion
 Recovery from excess alcohol consumption and vitamin B12 and folate
deficiency
 diabetes mellitus, increased blood lipids or cholesterol levels, increased
platelet levels, and smoking.
 Rheumatoid arthritis
 Renal failure
 Chronic pancreatitis

14.  1. Platelet counts normally increase at high
altitudes; exercise, trauma, or excitement;
and in winter.
 2. Platelet counts normally decrease before
menstruation and during pregnancy.

15.  avoiding contact sports
 avoiding activities with a high risk of bleeding.
 limiting alcohol consumption
 stopping or switching medications that affect
platelets, including aspirin and ibuprofen
 blood or platelet transfusions
 changing medications that are causing a low
platelet count
 corticosteroids to block platelet antibodies
 drugs that suppress your immune system
 a splenectomy, or the surgical removal of the
spleen