Anatomy Basic Question and Answer

Question :  What is the definition of human anatomy?

Ans : Human anatomy is one of the basic essential sciences of medicine. The discipline of anatomy is divided into macroscopic and microscopic anatomy. Macroscopic anatomy, or gross anatomy, is the examination of an animal's body parts using unaided eyesight.

Question :  What is anatomical structure?

Ans : An anatomical structure is a part of an organism, mainly a body. Simple as that. For example, a bone is an anatomical structure, a vein, an artery, a nerve, an organ, a ligament, etc. Or more specifically a part of a part of the body is also an anatomical structure. The left atrium of the heart, the right lobe of the liver, the left Conium of the femur etc.

How to position of Human Body ?

Ans : All the organs making up the human body are protected by the skin, which forms its outer covering. The skin is the largest organ of the body.

 
Man : Male human being producing cells able to fertilize the ovum (egg); the male’s skeleton is generally larger and heavier than that of the female.

 

Anterior View

  

Posterior View

Woman : Human being of the female sex capable of conceiving children from an ovum (egg) fertilized by a spermatozoon (sperm, the reproductive male cell) .

 

Anterior View 

 

Posterior View

Blood

Description Of Blood

Blood is the life sustaining "river of life" that flows within our bodies. It transports everything that must be carried from one place to another within the body nutrients, and body heat through blood vessels. Man recognized that blood was vital, and its loss was always considered to be a possible cause of death.

BLOOD COMPOSITION AND FUNCTION :

Blood is a thick, or viscous, substance composed of :

A. A fluid portion (plasma) in which

B. Living cells (formed elements) are suspended.

PLASMA :

Plasma (plaz'mah), which is approximately 90% water, is the liquid part of the blood. Over 100 different substances are dissolved in the plasma.

Composition of plasma varies continuously as cells remove or add substances to the blood.However, assuming a normal healthy diet, the composition of plasma is kept relatively constant by various homeostatic mechanisms of the body.

When the blood starts to become too acid (acidosis) or too basic (alkalosis), both the respiratory system and kidneys are called into action to restore it to its normal slightly alkaline pH range of 7.35 - 7.45.

In addition to transporting various substances around the body, plasma has another important role  - it helps distribute body heat evenly through the body tissues.

FORMED ELEMENTS :

Three types of formed elements, or blood corpuscles are present in the blood.

1.The most numerous are erythrocytes ( RBCs ) which are oxygen-carriers.

2.Leukocytes ( WBCs) are part of the body's immune system.

3.Thrombocytes or platelets help repair leaks in the blood vessels.

Formed elements make up 40%-45% of whole blood whereas plasma accounts for the remaining 55%-60%.

Only WBCs are complete cells

RBCs have no nuclei or organelles, and platelets are just cell fragments

Most formed elements survive in the bloodstream for only a few days

Most blood cells do not divide but are renewed by cells in bone marrow

ERYTIlROCYTES :

Erythrocytes, or red blood cells (RBCs), are small cells with a distinct biconcave disk shape. RBCs are anucleate. are unable to divide and have a limited lift span of 100-120days.

When mature and circulating in the blood, RBCs are literally sacs of hemoglobin molecules.

Hemoglobin (Hb) transports the bulk of the oxygen that is carried in the blood.

After that time, they begin to fragment, or fall apart, and their remains are eliminated by the spleen, liver, and other body tissues.

Lost cells are replaced more-or-Iess continuously by the division of cells called hemocytoblasts, located in the red bone marrow.

The rate of RBC production,hemopoiesis is controlled by a hormone, erythropoietin.

Which released by the kidneys in response to decreasing oxygen levels in the blood.

RBCs outnumber white blood cells by about 1000 to 1 and are the major factor contributing to blood viscosity.

Production of Erythrocytes :

Hematopoiesis –blood cell formation

Hematopoiesis occurs in thered bone marrow of the:

Axial skeleton and girdles

Epiphyses of the humerus and femur

Fate and Destruction of Erythrocytes :

The life span of an erythrocyte is 100–120 days

Old erythrocytes become rigid and fragile, and their hemoglobin begins to degenerate

Dying erythrocytes are engulfed by macrophages

Heme and globin are separated and the iron is reused

Heme is degraded to a yellow pigment called bilirubin

The liver secretes bilirubin into the intestines as bile

The intestines metabolize it into uro bilinogen

This degraded pigment leaves the body in feces, in a pigment called stercobilin

Globin is metabolized into amino acids and is released into the circulation

Hb released into the blood is captured by haptoglobin and phgocytized

Erythrocytes (RBCs) :

Although the numbers of RBCs in the circulation do vary, there are normally 4.5-5.5million cells per cubic millimeter of blood.

(Acubic millimeter [mm3] is a very tiny drop of blood, almost not enough to be seen.)

When thenumber of RBC/mm increases, blood viscosity increases.

Similarily; as the number of RBCs decreases, blood thins and flows more rapidly.

  

Erythrocyte Disorders :

1. Anemia: Is a decrease in the oxygen-carrying ability of the blood.

May be result of:

A. A lower than normal number of RBCs or,

B. A lower than normal hemoglobin content in the RBCs.

·It is a symptom rather than a disease itself

·Blood oxygen levels cannot support normal metabolism

·Signs/symptoms include fatigue, paleness, shortness of breath, and chills

Some types of anemia :

> Hemorrhagic anemia : result of acute or chronic loss of blood

>Hemolytic anemia : prematurely ruptured erythrocytes

>Aplastic anemia : destruction or inhibition of red bone marrow

Iron deficiency anemia results from :

A secondary result of hemorrhagic anemia

Inadequate intake of iron containing foods

Impaired iron absorption

Pernicious anemia results from :

Deficiency of vitamin B12

Lack of intrinsic factor needed for absorption of B12

Treatment is intramuscular injection of B12

Thalassemias - absent or faulty globin chain in hemoglobin

Erythrocytes are thin, delicate, and deficient in hemoglobin

Sickle cell anemia results from : defective gene coding for an abnormal hemoglobin called hemoglobinS (HbS)

HbS has a single amino acid substitution in the beta chain 

2. Polycythemia: Is an abnormal increase in number of erythrocytes ( RBCs).

May be result from:

A. Bone marrow cancer or,

B. Living at a high altitudes where less oxygen is available (secondary polycythemia).

The problem that results from excessive number of RBCs is increased viscosity of blood, which causes it to flow sluggishly in the body.

Leukocytes (WBCs) :

Basically WBCs are the blood's protective "movabie army." which helps protect the body from damage by bacteria, viruses, and tumor cells.

Leukocytes, the only blood components that are complete cells:

Are less numerous than RBCs and average from 5000 - 10,000 cells mm3

WBCs are more like most body cells than RBCs are that is, they contain nuclei

Make up 1% of the total blood volume

Can leave capillaries via diapedesis

Move through tissue spaces

Leukocyte Disorders :

1.Leukocytosis : WBC count over 10,000 per cubic millimeter

Normal response to bacterial or viral invasion

2.Leukemia : (literally, white blood) is a situation in which the

bone marrow becomes cancerous, and huge numbers of WBCs are turned out rapidly.

Classification of Leukocytes :

The WBCs are classified into two major groups, depending on whether or not they contain

Visible granules in their cytoplasm:

A. Granulocytes \–neutrophils, eosinophils, and basophils :

They are formed in red bone marrow as RBCs

Contain cytoplasmic granules that stain specifically (acidic,basic, or both)

Are larger and usually shorter-lived than RBCs

Have lobed nuclei

Are all phagocytic cells

1. A. Neutrophils

Neutrophils have two types of granules that:

Take up both acidic and basic dyes

Give the cytoplasm a lilac color

Contain peroxidases, hydrolytic enzymes, and defensins (antibiotic-like proteins)

Active phagocytes; their number increases rapidly during short-term or acute infections

2. A. Eosinophils

Eosinophils account for 1–3% of WBCs

Have red-staining, bilobed nuclei connected via a broad band of nuclear material

Have red to crimson (acidophilic) large, coarse, lysosome-like granules

Lead the body’s counterattack against parasitic worms

3. A. Basophils

Basophils account for 0.5% of WBCs and:

Cytoplasm has a few large granules, which stain deep purple with Wright's stain, large U or S shaped nucleus with constrictions, which stains dark blue

Granules believed to contain histamine (a vasodilator chemical ) and heparin (an anticoagulant), which are discharged on exposure to foreign substances (bacteria, viruses, and toxins)

B. Agranulocytes –lymphocytes and monocytes:

Lack visible cytoplasmic granules

They also arise from hemocytoblasts but migrate to lympnatic tissues.

Are similar structurally, but arefunctionally distinct and unrelated cell types

Have spherical (lymphocytes) or kidney-shaped (monocytes)nuclei.

        1. B. Lymphocytes :

Account for 20% -35% of WBCs and:

Have large, dark purple, circular nuclei with a thin rim of blue cytoplasm

2.B.Monocytes :

account for 3–8% of leukocytes

They are the largest leukocytes

  

Platelets :

Platelets are fragments of megakaryocytes with a blue-staining outer region and a purple granular center.

The normal platelet count in blood is 300,000 mm3.

Platelets are needed for the clotting process that occurs inplasma when blood vessels are ruptured or broken.

Genesis of Platelets :

The stem cell for platelets is the hemocytoblast.

The sequential developmental pathway is hemocytoblast, megakaryoblast, promegakaryocyte, megakaryocyte, and platelets.

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Muscles

Description Of Human Muscles

Muscles : 

Muscle is the contractile tissue which produces movements. Derived from the mesodermal layer of embryonic germ cells.

  

Types of muscles : 

 

Classification of Muscles

Morphological classification (based on structure)

1.  Striated

v                    Skeletal muscle

v                    Cardiac muscle

2.  Non striated or smooth

v                    Smooth muscle

Functional classification

1.  Voluntary

v                    Skeletal muscle

2.  Involuntary

v                    Cardiac muscle

v                    Smooth muscle

 

CARDIAC MUSCLE :

Cardiac muscle consists of muscle cells with one centrally placed nucleus.
Nuclei are oval, and located centrally in the muscle cell.

Cardiac muscle is innervated by the autonomic nervous system.

Cardiac muscle exhibits cross-striations.

Cardiac muscle is also called involuntary striated muscle.

Cross-striations in cardiac muscle are less distinct than skeletal muscle.

In contrast to skeletal muscle cells, cardiac muscle cells often branch at acute angles

They are connected to each other by specializations of the cell membrane in the region of the intercalated discs.

Intercalated discs invariably occur at the ends of cardiac muscle cells.

   

Smooth Muscle :

Smooth muscle consists of spindle shaped cells of variable size.

The largest smooth muscle cells occur in the uterus during pregnancy. The smallest are found around small arterioles.

Smooth muscle cells contain one centrally placed nucleus.

The innervation of smooth muscle is provided by the autonomic nervous system.

Smooth muscle makes up the visceral or involuntary muscle.

Skeletal Muscle :

Most abundantly attached to Skeleton.

Showing cross striation under the microscope.

Supplied by somatic nerves, therefore under the voluntary control.

Respond quickly to stimuli, producing rapid contraction, that’s why fatigue quickly.

Skeletal muscle consists of very long tubular cells (also called muscle fibers).

Skeletal muscle fibers contain many peripherally placed nuclei.

Skeletal muscle fibers show in many preparations characteristic cross-striations. It is therefore also called striated muscle.

Skeletal muscle is innervated by the somatic nervous system.

Skeletal muscle makes up the voluntary muscle.

   

Coverings of muscle :

Epimysium

Entire muscle is surrounded by a connective tissue called the Epimysium.

Fascicles

Fascicles are actually bundles of individual muscle cells or muscle fibers.

Perimysium

Fascicles are surrounded by a connective tissue sheath called the perimysium.

Muscle fibers

Each fascicle is made up of several muscle cells known as muscle fibers.

Endomysium

Each muscle cell or muscle fiber is surrounded by a connective tissue sheath known as the endomysium.

  

Parts of Skeletal Muscle :

Origin

The one end of muscle which remains fixed during contraction (Proximal End)

Insertion

The other end which moves during contraction (Distal End)

Belly

Central contractile part.

Tendon or aponeurosis

Fibrous non-contractile part. When it is cord like called as tendon or when broad sheath like, aponeruosis

   

Structural Classification of Skeletal Muscle :

On the basis of arrangement of fibers

Parallel

1- Quadrilateral

2- Rhomboid

3- Strap like

4- Fusiform

Parallel Muscle :

The muscle fasciculi are parallel to the line of pull

Consists of parallel fibers all of equal size

The range of movement is maximum

The force of contraction is less

When muscle contracting all the muscle fibers are contacting with equal length

Structural Classification of Skeletal Muscle :

On the basis of arrangement of fibers

B- Oblique

1- Unipennate

2- Bipennate

3- Multipennate

4- Circumpennate

5- Triangular

6- Spiral or Twisted

Oblique Muscle :

The muscle fasciculi are oblique to the line of pull

Consists of oblique fibers (feather like) muscle fibers are variable size (some are shorter while other are loner) 

The range of movement is reduced

The force of contraction is powerful 

When muscle contracting all the muscle fibers are contacting with unequal length

Functional Classification of Muscle :

Agonist

Antagonist

Synergist

Fixator

Agonist

Agonist is kind of muscle that causes movement to occur. It creates the normal range of movement in a joint by contracting.

Agonists are also referred to as "prime movers" since they are the muscles that are primarily responsible for generating movement.

Antagonist

An antagonist is a kind of muscle that acts in opposition to the movement generated by the agonist and is responsible for returning a limb to its initial position.

Synergist

Synergist is a kind of muscle which perform, or assist in performing, the same set of joint motion as the agonists.

> Synergists are muscles that act on movable joints.

> Synergists are sometimes referred to as "neutralizers" because they help cancel out, or neutralize, extra motion from the agonists to make sure that the force generated works within the desired plane of motion

  

Fixator muscle

A muscle that acts as a stabilizer of one part of the body during movement of another part.

Fixator  

A fixator holds the origin of the agonist, stable. E.g., abducting arm deltoid is abductor, fixators are other flexors keeping the scapula in position e.g. rhomboids.

Blood supply and nerve supply of muscle :

Arteries supply the structure to which the muscles are in contact.

Nerve supply

Motor nerves enter the fleshy portion of muscle, almost always from the deep portion.

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