February 2019 | Biology Hubspot - Definition and Examples of Biology Terms


Blog For Biology and Medical Related Help


Thursday, February 28, 2019

What is Synovial joint

February 28, 2019 0

Synovial joint

The synovial joint is freely movable so it is functionally diarthrosis in nature. It differs from the rest of the joints due to the presence of a  characteristic
feature called the synovial cavity.
The articulating bones of the synovial joint are covered by a layer of hyaline cartilage called articular cartilage. It covers them but doesn't unite or bind them together. Articular cartilage reduces friction and absorbs shock during joint movements.

Articular capsule

It encloses the synovial cavity and unites the articulating bones of the synovial joint with each other. It consists of two layers viz. outer fibrous membrane and inner synovial membrane.
The outer fibrous membrane attaches to the periosteum of the articulating bones and mostly consists of collagen fibers. Due to flexible nature allows considerable movement at a joint, provides great tensile strength to prevent bones from dislocation.
Bundles of fibers in the fibrous membrane, together called ligaments are one of the important means by which articulating bones in synovial joints are united to each other.
The inner synovial membrane is made up of elastic fibers and areolar connective tissue. This type of layer in certain synovial joints is associated with the accumulation of adipose tissue called articular fat pads e.g. fat pads in the knee.

Synovial fluid

Synovial fluid is secreted by the synovial membrane. It consists of two components hyaluronic acid and interstitial fluid.The former is secreted by the fibroblast-like cells present in the synovial membrane and the latter is filtered blood plasma.
Due to the lubricating property of the synovial fluid, it reduces friction between articulating bones and absorbs shock.
Synovial fluid provides nutrients and oxygen and removes carbon dioxide and wastes from articular cartilage (cartilages are avascular).
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Wednesday, February 27, 2019

What are the layers of the heart tissue ?

February 27, 2019 0
What are the layers of the heart tissue ?

What are the layers of the heart tissue

The heart consists of the following three layers viz epicardium, myocardium, endocardium.
Let’s explain these layers one by one.


It is the external layer of the heart that is also known by the visceral layer of serous pericardium. It is tightly attached to the surface of the heart and imparts smooth, slippery texture to its outer surface.


It is the middle layer of the heart that consists of cardiac tissue. The cardiac tissue like the smooth muscle is involuntary in nature and constitutes 95% of the heart.
The myocardium is involved in the pumping action of the heart.


 It is the inner most layer of the heart wall and is present over a thin layer of connective tissue.
The covering of endothelium over the heart chambers and valves provides them a smooth lining. In addition to that, it also lines the large blood vessels and minimizes surface friction as blood passes through the heart and blood vessels.
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Structure Of Nephron: Renal corpuscle and Renal tubule

February 27, 2019 0

Structure Of Nephron

The nephron is the structural and functional unit of the kidney. The nephron consists of two main parts viz. Renal corpuscle and Renal tubule.
The renal corpuscle helps in the filtration of blood plasma while as renal tubule acts as the receiving part of the filtered fluid.

Renal Corpuscle

Parts that constitute the renal corpuscle are glomerulus and glomerular capsule. The former is made up of the capillary network while as latter is a double-walled cup of epithelial tissue that envelops the glomerular network.

Renal Tubule

The renal tubule of the nephron consists of three parts namely proximal convoluted tubule(PCT), Loop of Henle, Distal convoluted tubule(DCT).

Proximal Convoluted Tubule

The proximal convoluted tubule of the nephron lies in the middle of the Bowman’s capsule and the U-turn Loop of Henle.
Its function is the resorption of various ions like Sodium, Chloride, and water from the filtrate.

Loop of Henle

The loop of Henle connects the proximal convoluted tubule (PCT) and distal convoluted tubule of the nephron. This part of the renal tubule consists of two limbs namely the descending loop of Henle and the ascending loop of Henle.
The part of the loop of Henle that dips into the renal medulla is called descending limb of the loop of Henle whereas the part that lies in the renal cortex is called the ascending loop of Henle.
The nephron is divided into two types based upon the location of the renal corpuscle and length of the loop of Henle. The two types are cortical nephron and juxtamedullary nephron.
The cortical nephron has a short loop of Henle and their renal corpuscle lies in the outer portion of the renal cortex. About 80-85% of the nephrons are cortical in nature.
The rest of the nephrons 15-25% are known as juxtamedullary nephrons. These nephrons have a long loop of Henle and their renal corpuscle lie deep within the cortex.

Distal Convoluted Tubule

The distal convoluted tubule of the nephron joins the loop of Henle with the collecting duct. The network of the collecting ducts unite and form papillary ducts which then drain into the minor calyces.
Collecting duct and papillary duct extend from the renal medulla of the nephron to the renal pelvis.

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Epithelial tissue | To the point

February 27, 2019 0

Epithelial tissue

The epithelial tissue consists of single or multiple cell layers that are arranged in sheets. It forms the covering and lining of various organs in the body.
The space between the adjacent plasma membrane of epithelial cells is quite small due to the closely packed arranged of cells.
The major functions of the epithelial tissue are grouped as under:
1) It acts as a barrier that controls the movements of materials into and out of the body.
2) It helps in the secretion of cell products via its secretory surfaces.
3) Protects the body from abrasive conditions of the environment.
The rate of cell division in epithelial tissue is quite high so that dead or injured cells can be removed or repaired quickly. It combines with the nervous tissue to form sense organs.
Epithelial tissue possesses its own nerve supply but lacks its own blood vessels. The connective tissue located adjacent to the epithelial tissue supplies nutrients and removes wastes from it. The exchange of substances occurs via diffusion.
The epithelial tissue is of two types:
a) Covering and lining epithelium: - This type of epithelial tissue forms covering around the skin, some internal organs, blood vessels, ducts and interior of the different body systems.
b) Glandular epithelium:- This type forms secreting portions of various body glands like thyroid gland, adrenal gland etc.

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Ureters | To the point

February 27, 2019 0


Ureters are two tube-like structures that transport urine from the renal pelvis of the kidney to urinary bladder by peristaltic movement of its muscles.
The ureters are thick walled, 25-30 cm in length and having a diameter in the range of 1mm- 10mm.
Ureters do not possess anatomical valve at the site of the opening into the urinary bladder but instead contain physiological valve which operates quite effectively.
When the urinary bladder is filled with urine it generates pressure that causes compression of oblique openings into the ureters by preventing backflow of urine.
If the physiological valve is not properly closed the microbes will travel from urinary bladder towards the kidney resulting infection of either one or both the kidneys.
The wall of ureters is made up of three layers viz. mucosa, muscularis, and adventitia.
The mucosa contains mucus secreted by its goblet cells which prevent cells from coming in contact with the urine.
The middle muscularis consists of inner longitudinal and outer circular layers of the smooth muscle fibers. The main function of muscularis is peristalsis.
The superficial layer adventitia consists of areolar connective tissue and different blood and lymphatic vessels. Its function is to anchor the ureters.
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Saturday, February 23, 2019

Classification Of Joints - Structural and Functional

February 23, 2019 0

Classification Of Joints

Joints are classified both structurally and functionally. The structural classification of joints is based on the two criteria
  • Whether there is a space between the articulating bones or not.

  • Type of the connective tissue that finds the articulating bones.

Structural classification of joints

  • Fixed or fibrous joint: - It lacks synovial cavity and the articulating bones are held together by the fibrous tissue. E.g. sutures in the skull bones, the joint between the tooth and jawbone (Gomphosis), syndesmosis is another fibrous joint between the radius-ulna and tibia-fibula.

  • Imperfect or cartilaginous joint: - It also lacks synovial cavity and the articulating bones are connected by either by hyaline cartilage or fibrocartilage.

    The examples of cartilaginous joints are pubic symphysis, ribs, sternum, epiphyseal plate, and intervertebral joints.

  • Freely movable or Synovial joint: - The characteristic feature that distinguishes this joint from others is the presence of synovial cavity between articulating bones. This cavity enables a wide range of movements.

    The articulating bones in a synovial joint are united together by an articular capsule and by accessory ligaments.

    Synovial joints include hip joint, shoulder joint, carpometacarpal joint, radio-carpal or wrist joint, elbow joint, knee joint etc…

  • Functional classification of joints

    • Synarthroses:- These are immovable joints and provide a strong articulation between bones for protection of vital organs.

    • Amphiarthroses: - These are slightly movable joints that allow a limited amount of movement.

    • Diarthroses: - Are freely movable joints and include all synovial joints of the body which provide the majority of body movements.
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Red blood cells: shape, cell size, count

February 23, 2019 0

Red blood cells

Red blood cells are also known by the other two names namely erythrocytes and RBCs.Red blood cells lack a nucleus (enucleated) and other cellular organelles but contain an important pigment called hemoglobin.

Red blood shape, cell size, count

These are biconcave or dumbbell-shaped measuring about 7-8 mm in length and 1-2 micrometers in thickness.
The number of Red blood cells per microliter or mm3 is called total red blood cell count and is measured by an instrument called hemocytometer.
The number of red blood cells in a healthy adult male is about 5.4 million per microliter of blood, and a healthy adult female has about 4.8 million per microlitre of blood.

Diseases caused by up or down RBC count

The red blood cells constitute 98% of the cells in the blood. The increase in the number of RBCs causes a disease called Polycythemia while a decrease in the number of RBCs causes a disease called Erythrocytopenia.
RBC Physiology
The red blood cells contain respiratory pigment called hemoglobin. The hemoglobin contains four atoms of iron in its heme portion each of which is capable of binding to the O2 molecule in a reversible form of reaction to form Oxyhaemoglobin.
The quantity of hemoglobin is measured in per hundred ml of blood by an instrument called Haemometer or haemoglobinometer. The normal value of hemoglobin is 14-16 grams per hundred ml of blood in males and 12-14 grams per hundred ml of blood in females.
The normal life span of red blood cells is 120 days. The aged or dead Red blood cells are destroyed in the spleen, thus it is called graveyard of RBCs. At any time 2.5 million red blood cells are destroyed per second and the same number is formed also.
The red blood cells are formed in the bone marrow under the influence of hormone erythropoietin secreted by kidneys the process called erythropoiesis.
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Tuesday, February 19, 2019

Function of the digestive system

February 19, 2019 0

Function of the digestive system

Function of the Digestive System is the breakdown of complex food molecules into smaller and simple ones that are easily absorbed by the body cells.

Organs that make the digestive system

Two groups of organs namely the Gastrointestinal (GI) tract and the accessory digestive organs constitute the digestive system.
The GI tract is a continuous tube-like structure that extends from the mouth to the anus. Its length is almost 5-7 meters in a normal person. The organs that constitute the GI tract are mouth, esophagus, stomach, small intestine, and large intestine.
The accessory digestive organs include the teeth, salivary glands, liver, gall bladder, and pancreas.

Processes performed by the digestive system

The digestive system in human beings performs six basic processes which are listed below:
  • Ingestion: - The process of taking food through the mouth into the gastrointestinal tract by activities like eating or drinking. In unicellular organisms, it takes place through the cell membrane.

  • Mixing and propulsion:- The walls of the gastrointestinal tract contain smooth muscles that generate alternating contractions and relaxations resulting in the mixing of food and also aid in the process of peristalsis that is the movement of food along the digestive tract.

  • Secretion: - The secretions from the walls of the gastrointestinal tract and accessory digestive organs prevent the growth of bacteria, help in the breakdown of complex substances, moist food and adjust the PH to the optimum level.

  • Digestion: - The process of Digestion is classified into two types:

    a) Mechanical Digestion: - It involves process mastication (food is crushed into pulpy mass) and peristalsis.

    b) Chemical Digestion:- It helps in the breakdown of large carbohydrates, lipids, proteins, and nucleic acids into smaller molecules via enzymes secreted by various parts of the digestive system.

  • Absorption: - This process mostly occurs in the small intestine. The small intestine contains microvilli and finger-like projections called villi. Both of these increase surface area so that more nutrients can be absorbed.

  • Defecation: - The final step in digestion, undigested substances, wastes, bacteria and digested materials that were not absorbed during the process are removed from the body as faces.

Also Read:

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Sunday, February 17, 2019

Things you should not do while studying for the exam -Exam Tips

February 17, 2019 0
Today I’m going to share with you an important article that is “Things you should not do while studying for the exam”

#1: “Don't copy others”

Follow your own time table and be consistent. Don’t copy the timetable framed by your friend, it might be controversial to you.

 At the time he has planned to study you might be busy in other kinds of work…

 Be cautious of night-owl persons do not follow them. Take enough sleep but not too much.

Avoiding sleep increases the risk of disorders like high blood pressure, cardiovascular disease, diabetes, depression, and obesity.

 #2: “Don’t change your books”

During the period of studying for the examination, we all had a habit of calling the friend asking him about exam preparation, books he is using, the syllabus finished or not.

 And if he told I had finished the syllabus using xyz books .we starting thinking in our mind perhaps the books that he has consulted are easy that is why he had completed the syllabus earlier.

Later we also start preparing from the same book which results in the storage of newly studied information into short term memory and makes our mind frustrated while answering the questions during the time examination.

#3: “Stop doing mugging up be logical”

Most students use the technique of mugging up the subjects before exams for getting higher marks.

 But according to my perspective, those marks are useless and will spoil your bright career.

Try to get your concepts clear, it may take time but once your concepts are clear you will be free from the time-wasting mugging up process.
#4: “Say goodbye to junk foods”
Eating a lot of junk foods especially during the examination may make you feel sleepy and sick.

So take light meals during the period of exam preparation.

“Health is like oil of a car and without oil, a car cannot even start”. So try to stay healthy...
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Sunday, February 3, 2019

Oxygen transport: hemoglobin affinity for oxygen

February 03, 2019 1

Oxygen transport? 

The solubility of oxygen in water is little that is why only 1.5% of oxygen is dissolved in blood plasma. The remaining portion of oxygen (98.5%) is transported by hemoglobin as Oxyhaemoglobin (Hb-O2) within Red Blood Cells.
The hemoglobin contains four atoms of iron in its heme portion each of which is capable of binding to the O2 molecule in a reversible form of reaction to form Oxyhaemoglobin.
The binding of O2 with hemoglobin depends on an important factor that is partial pressure of oxygen.
When the partial pressure is high, hemoglobin binds with large amounts of O2 and is almost 100% saturated When the partial pressure of oxygen is low, hemoglobin is only partially saturated (i.e. less amount of Hb is converted to Hb-O2).
In pulmonary capillaries where the partial pressure of oxygen is high a lot of oxygen binds to hemoglobin whereas in tissue capillaries where the partial pressure of oxygen is lower, hemoglobin doesn’t hold a greater amount of oxygen and the dissolved oxygen is unloaded through diffusion into tissue cells.

Factors affecting the affinity of Hemoglobin for oxygen? 

  1. Acidity: As acidity increases (PH decreases) the affinity of hemoglobin for oxygen decreases and oxygen dissociates readily from hemoglobin.
  2. The partial pressure of carbon dioxide: The effect of the partial pressure of carbon dioxide is similar to that of an increase in acidity. As the partial pressure of carbon dioxide raises the affinity of hemoglobin for oxygen decreases.
  3. Temperature: An increase in temperature results in a decrease in the affinity of hemoglobin for oxygen. In contrast during hypothermia (lower body temperature), the larger amount of oxygen binds to hemoglobin.
  4. BPG: It is called 2,3 bisphosphoglycerate, a substance formed in Red Blood Cells during the breakdown of glucose to produce ATP in a process called glycolysis. It decreases the affinity of hemoglobin for oxygen.

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Saturday, February 2, 2019

Pulmonary Ventilation: Inhalation and Exhalation

February 02, 2019 0

What Is Pulmonary ventilation? 

Pulmonary ventilation is also known by the more common term namely breathing. In this process, the alternating pressure differences generated by contraction and relaxation of respiratory muscles causes the air exchange between alveoli of the lungs and atmosphere.
The amount of air exchange and effort required for breathing is also affected by the other three factors viz alveolar surface tension, compliance of the lungs and airway resistance.

Pressure Changes During Pulmonary Ventilation? 

The air moves into and out of the lungs due to the air pressure difference between the inside of the lungs and outside the environment.
When the air pressure inside the lungs is lower than the air pressure outside the environment air rushes into the lungs(inhalation) and when the air pressure difference is in opposite direction air moves out of the lungs(exhalation).
Let's explain this in detail one by one
The process of breathing in is known as inhalation, it is also known as inspiration. For the process of inhalation to occur the air pressure inside the lungs must be lower than the air pressure outside the environment. This condition (air pressure lower inside the lungs) is achieved by expanding the lungs.
The two important muscles that are involved in expanding of the lungs during inhalation are diaphragm and external intercostals.
  1. Diaphragm: The dome-shaped diaphragm contracts during inhalation. The contraction changes its structure from dome-shaped to flatten which results in a larger thoracic cavity and more space for the lungs.The Contraction of Diaphragm accounts for about 75% of the air to enter into the lungs.
  2. External Intercostals: The external intercoastal is responsible for uplifting the ribs during inhalation which results in an increase in the volume of the chest cavity. This increase in volume leads to a decrease in intra-alveolar pressure, creating a pressure lower than atmospheric pressure.The Contraction of external intercostals accounts for about 25% of the air to enter into the lungs.


The breathing out called Exhalation (expiration) also occurs due to the air pressure difference between inside the lungs and outside the environment.But the air pressure difference in this process is in opposite direction in contrast to inhalation.
The exhalation is a passive process during Quiet breathing because no muscular activity is involved in it, as it results due to the elastic recoil of the chest wall and lungs both of which have an inherent tendency to recoil back after they are stretched.
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