৪৮তম বিশেষ বিসিএস [স্বাস্থ্য] ⎯ ডেন্টাল অংশ [Archived]

The nine essential amino acids are: Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine. 

the nutrient antioxidants, vitamins A, C and E, and the minerals copper, zinc and selenium.

Ferritin and hemosiderin are storage form and transferrin is transport form

Functional Iron:
Definition:
Functional iron refers to iron that is actively involved in the body's metabolic processes, performing specific functions.  
Examples:
Hemoglobin: The protein in red blood cells that carries oxygen from the lungs to the rest of the body.  
Myoglobin: A protein in muscle cells that stores oxygen for muscle activity.  
Iron-containing enzymes: Iron plays a crucial role in the activity of many enzymes involved in various metabolic pathways, including energy production.  
Importance:
Functional iron is vital for carrying out essential biological processes. A deficiency in functional iron can lead to fatigue, weakness, and impaired oxygen delivery to tissues.  
Location:
Functional iron is found within cells, primarily in red blood cells (hemoglobin), muscle cells (myoglobin), and within the active sites of enzymes.  
Transport Iron:
Definition: Transport iron is the form in which iron is moved throughout the body, from absorption in the gut to storage sites and to where it's needed for functional purposes.  
Key Protein: The primary protein involved in iron transport is transferrin.  
Process: Iron is absorbed in the intestines, then bound to transferrin in the blood, which carries it to the liver, bone marrow, and other tissues.  
Location: Transport iron is found in the blood, bound to transferrin.  
Importance: Efficient iron transport is crucial for delivering iron to cells for various functions, including hemoglobin synthesis in the bone marrow and other metabolic processes.

Examples of Transcellular Fluid:  
Cerebrospinal fluid (CSF): Surrounds the brain and spinal cord, providing protection and support.  
Synovial fluid: Found in joints, acting as a lubricant and shock absorber.  
Aqueous and vitreous humors of the eye: Maintain the shape of the eye and play a role in vision.  
Gastrointestinal fluids: Digestive secretions and fluids within the lumen of the intestines.  
Pleural, pericardial, and peritoneal fluids: Serous fluids lining the respective body cavities (pleural = lungs, pericardial = heart, peritoneal = abdomen).  
Urinary bladder urine: Fluid within the bladder prior to excretion. 

ABC biochemistry 10th ed. P- 249

Production of Essential Substances:
Proteins:
The liver synthesizes vital proteins like albumin (which helps maintain fluid balance and transport substances), and clotting factors (essential for stopping bleeding).  
Bile:
Bile, produced by the liver, is stored in the gallbladder and released into the small intestine to aid in the digestion and absorption of fats and fat-soluble vitamins.  
Blood Clotting Factors:
The liver produces proteins that are essential for blood clotting, preventing excessive bleeding.  
Cholesterol:
The liver produces cholesterol, a component of cell membranes and a precursor for other important molecules.  
2. Metabolic Functions:
Nutrient Processing:
The liver processes nutrients from digested food, converting them into usable forms, storing energy (as glycogen), and regulating blood sugar levels.  
Carbohydrate Metabolism:
The liver plays a key role in regulating blood glucose levels by storing glucose as glycogen and releasing it when needed.  
Amino Acid Metabolism:
The liver converts amino acids, the building blocks of proteins, into other compounds or uses them to produce new proteins.  
Lipid Metabolism:
The liver helps regulate fat metabolism, producing cholesterol and other substances needed for fat transport and utilization.  
Detoxification:
The liver filters toxins from the blood, including drugs, alcohol, and other harmful substances, converting them into less harmful forms or preparing them for excretion.  
Waste Removal:
The liver converts ammonia, a toxic byproduct of protein metabolism, into urea, which is then excreted by the kidneys.  
3. Other Important Functions:
Hemoglobin Breakdown: The liver processes old red blood cells and breaks down hemoglobin, recovering iron for reuse.
Vitamin Storage: The liver stores certain vitamins, including A, D, B12, and others.

Lingual nerve is a branch of the mandibular division of the trigeminal nerve (CN V3).
It provides general sensation (touch, pain, temperature) to the anterior two-thirds of the tongue, floor of the mouth, and lingual gingiva.
It carries taste fibers from the anterior two-thirds of the tongue via the chorda tympani (branch of facial nerve).
It also carries parasympathetic secretomotor fibers to the submandibular and sublingual glands.
The nerve lies medial to the mandibular ramus and is vulnerable during dental procedures like third molar extraction.

Causes of Metabolic Acidosis:  
1. Increased Acid Production:
Diabetic Ketoacidosis (DKA):
In uncontrolled diabetes, the body produces excess ketones, which are acidic, leading to metabolic acidosis.  
Lactic Acidosis:
A buildup of lactic acid can occur due to various factors like strenuous exercise, certain diseases (e.g., liver failure, sepsis), or drug/toxin ingestion.  
Ingestion of Acids:
Certain substances, such as salicylates (found in aspirin), methanol, and ethylene glycol (found in antifreeze), can directly increase the acid load in the body.  
Severe Dehydration:
Dehydration can lead to a buildup of waste products, contributing to metabolic acidosis.  
2. Reduced Acid Excretion:  
Kidney Failure:
Impaired kidney function, whether acute or chronic, can prevent the body from adequately excreting acids, leading to acidosis.  
Renal Tubular Acidosis (RTA):
This is a specific type of kidney disorder where the kidneys cannot properly excrete acids or reabsorb bicarbonate.  
3. Bicarbonate Loss:  
Severe Diarrhea:
Loss of bicarbonate in the stool can deplete the body's base, leading to metabolic acidosis.  
Other Gastrointestinal Losses:
Conditions like intestinal fistulas or ileostomies can also lead to bicarbonate loss. 

 Explanation:
Vitamin C deficiency, also known as scurvy, results from insufficient ascorbic acid, which is essential for collagen synthesis, wound healing, and maintaining the integrity of connective tissues, especially in gums and blood vessels.

Vitamin C deficiency → classic signs:

Gum bleeding  /gum hyperplasia
Loose teeth
Poor wound healing
Perifollicular hemorrhages
Fatigue
Therefore, গ) Gum hyperplasia is the correct feature of vitamin C deficiency.

Erythropoietic vitamins are those that play a vital role in the formation and development of red blood cells (RBCs). Vitamin B12, vitamin B6, and folic acid are all directly or indirectly involved in erythropoiesis. Vitamin B12 is essential for DNA synthesis and proper maturation of RBCs, and its deficiency can lead to megaloblastic anemia. Similarly, folic acid is crucial for nucleic acid synthesis and also prevents megaloblastic changes in red cell precursors. Vitamin B6 supports the synthesis of heme, the iron-containing component of hemoglobin, and its deficiency can result in sideroblastic anemia. In contrast, vitamin K does not have a role in erythropoiesis. Instead, it is essential for the synthesis of clotting factors that help in blood coagulation. Therefore, among the options, vitamin K is not considered an erythropoietic vitamin.

Prothrombin time and serum albumin are test for synthetic function 
Ref. ABC Biochemistry,  p-465

Mandible develops mainly by intramembranous ossification from the first branchial arch.
The body of the mandible forms by intramembranous ossification around Meckel’s cartilage.
The condylar, coronoid, and angular processes develop by endochondral ossification from cartilage.

Hyaline Cartilage

- Most common 
- Bluish-white and glassy under microscope
- Type II collagen fibers
- Chondrocytes lie in lacunae, scattered in a firm matrix
- Avascular; nutrients diffuse through matrix
- Surrounded by perichondrium (except at articular surfaces)

Locations:
- Articular surfaces of joints
- Costal cartilages (ribs to sternum)
- Nasal cartilage
- Larynx (parts like thyroid, cricoid)
- Trachea and bronchi
- Epiphyseal growth plates (in growing bones)

Functions:
- Provides smooth surface for joint movement
- Supports respiratory tract
- Assists in bone growth (endochondral ossification)

Coronal (Frontal) plane divides the body into front (anterior) and back (posterior) parts.

TMJ Movements (Temporomandibular Joint):

- Opening & Closing (Depression & Elevation):
Opening – Lateral pterygoid
Closing – Masseter, temporalis, medial pterygoid

- Protrusion & Retrusion:
Protrusion – Lateral pterygoid
Retrusion – Posterior fibers of temporalis

- Lateral (Side-to-Side) Movement:
Lateral pterygoid (opposite side)
Temporalis & masseter (same side)

TMJ allows hinge (rotation) and gliding (translation) actions.

Ossification Classification:

1. Based on Process:
- Intramembranous ossification:
Bone forms directly from mesenchymal tissue.
Example: Flat bones of skull, mandible (partially).

- Endochondral ossification:
Bone replaces a cartilage model.
Example: Long bones like femur, humerus.

2. Based on Time of Appearance:
- Primary ossification center:
Appears early in fetal life; diaphysis in long bones.

- Secondary ossification center:
Appears after birth; forms epiphysis.

3. Based on Location:
- Cortical ossification: compact bone.

- Cancellous ossification: spongy bone.

Branches of External Carotid Artery (ECA): 8 in number

Anterior branches – Superior thyroid, Lingual, Facial
Posterior branches – Occipital, Posterior auricular
Medial branch – Ascending pharyngeal
Terminal branches – Maxillary, Superficial temporal

Genotype is the genetic makeup of an organism, while phenotype is the observable trait.

Here’s a concise list of important syndromes with their genotypes:

Down Syndrome
- Genotype: Trisomy 21 (47,XX+21 or 47,XY+21)
- Features: Intellectual disability, flat facial profile, congenital heart defects

Turner Syndrome
- Genotype: 45,X (monosomy X)
- Features: Short stature, webbed neck, infertility, only in females

Klinefelter Syndrome
- Genotype: 47,XXY
- Features: Tall stature, hypogonadism, gynecomastia, male infertility

Edward Syndrome
- Genotype: Trisomy 18
- Features: Severe developmental delay, clenched fists, rocker-bottom feet

Patau Syndrome
- Genotype: Trisomy 13
- Features: Midline facial defects, polydactyly, severe intellectual disability

Bell's Palsy is an acute, unilateral, lower motor neuron facial nerve (cranial nerve VII) paralysis.

Sodium-Potassium Pump (Na⁺/K⁺ ATPase):

- It is an active transport mechanism present in all animal cells.
- It uses ATP to transport ions against their concentration gradients.
- For every 1 ATP molecule hydrolyzed, 3 sodium ions are pumped out of the cell and 2 potassium ions are pumped into the cell.
- Maintains resting membrane potential, cell volume, and electrochemical gradients.
- Essential for nerve impulse transmission and muscle contraction.

Special sense organs:

Eye – Detects light and color; contains retina with rods and cones.
Ear – Cochlea for hearing, vestibular apparatus for balance.
Nose – Olfactory epithelium detects smell; signals via olfactory nerve.
Tongue – Taste buds sense sweet, sour, salty, bitter, umami; innervated by facial, glossopharyngeal, vagus nerves.
Skin – Contains receptors for touch, pressure, temperature, and pain.

Sympathetic vs Parasympathetic Functions

Sympathetic (Fight or Flight):
- Increases heart rate
- Dilates pupils
- Dilates bronchi
- Inhibits salivation & digestion
- Stimulates glucose release
- Relaxes bladder
- Ejaculation in males

Parasympathetic (Rest and Digest):
- Decreases heart rate
- Constricts pupils
- Constricts bronchi
- Stimulates salivation & digestion
- Promotes glycogen synthesis
- Contracts bladder
- Erection in males

Hormonal Regulation of Blood Pressure:

1. Renin-Angiotensin-Aldosterone System (RAAS):
- Renin (from kidneys) → Angiotensin II → vasoconstriction
- Aldosterone → Na⁺ & water retention → ↑ blood volume & pressure

2. Antidiuretic Hormone (ADH):
- Increases water reabsorption in kidneys → ↑ blood volume → ↑ BP

3. Atrial Natriuretic Peptide (ANP):
- Released by heart atria → promotes Na⁺ & water excretion → ↓ blood volume & BP

4. Catecholamines (Adrenaline/Noradrenaline):
- From adrenal medulla → vasoconstriction & ↑ cardiac output → ↑ BP

5. Cortisol:
- Enhances vasoconstrictor response → supports BP maintenance during stress

Functions of Parathyroid Hormone (PTH):

• Increases blood calcium levels
• Stimulates osteoclasts → bone resorption
• Enhances calcium reabsorption in kidneys
• Promotes activation of Vitamin D in kidneys → increased intestinal calcium absorption
• Decreases phosphate reabsorption in kidneys → increased phosphate excretion

Adrenocorticotropic Hormone (ACTH) & Feedback Mechanism:

- Negative feedback
↑ Cortisol levels in blood inhibit the release of ACTH from the pituitary
Also inhibits CRH (Corticotropin-releasing hormone) from the hypothalamus
This maintains hormone balance and prevents overproduction of cortisol.

T3 (Triiodothyronine) & T4 (Thyroxine):

- Secreted by: Thyroid gland
- T4 is secreted in larger amounts; T3 is more active
- Most T4 is converted to T3 in peripheral tissues

Cortisol Functions:
- Increases blood glucose by promoting gluconeogenesis
- Breaks down protein & fat (catabolic effect)
- Anti-inflammatory and immunosuppressive
- Helps in stress response
- Maintains blood pressure and vascular tone

Important features of Hypothyroidism:

- Fatigue and weakness
- Weight gain despite poor appetite
- Cold intolerance
- Dry, coarse skin
- Constipation
- Depression or slow mental activity
- Bradycardia (slow heart rate)
- Hoarseness of voice
- Puffy face, periorbital swelling
- Menstrual irregularities
- Hair thinning or hair loss (including lateral eyebrows)
- Goiter may be present
- In severe cases: Myxedema (non-pitting edema)

In children, it can lead to growth retardation and delayed milestones (cretinism if congenital).

Resorption in nephron :

- Proximal Convoluted Tubule: 65-70% of filtered water, sodium, glucose, amino acids, and bicarbonate.

- Loop of Henle:
- Descending limb: water reabsorbed.
- Ascending limb: Impermeable to water; reabsorbs sodium, potassium, and chloride.

- Distal Convoluted Tubule: sodium and chloride; regulated by aldosterone.
- Collecting Duct: water under ADH influence; sodium reabsorption regulated by aldosterone.

ADH (Antidiuretic Hormone)/Vasopressin functions:

- Increases water reabsorption in kidneys (collecting ducts)
- Helps concentrate urine
- Maintains blood pressure and blood volume
- Acts on V2 receptors in renal tubules
- Promotes insertion of aquaporin-2 channels
- Released in response to increased plasma osmolality or low blood volume
- Helps prevent dehydration and volume depletion

Baroreceptors
- Stretch-sensitive receptors in carotid sinus and aortic arch
- Detect blood pressure changes
- Help regulate heart rate and vessel diameter via autonomic reflexes

Chemoreceptors
- Central: Located in medulla, respond mainly to CO₂ and pH changes in cerebrospinal fluid
- Peripheral: Located in carotid and aortic bodies, respond to low O₂, high CO₂, and low pH in blood
- Influence respiratory rate and depth to maintain blood gas balance

The kidneys retain bicarbonate to buffer excess H⁺ in chronic respiratory acidosis.

Pathophysiology of Diabetic Ketoacidosis
- Insulin deficiency → increased lipolysis → free fatty acids → liver converts to ketone bodies (acetoacetate, β-hydroxybutyrate).
- Ketones accumulate → metabolic acidosis.
- Hyperglycemia → osmotic diuresis → dehydration & electrolyte loss.

Causes/Triggers:
- Missed insulin doses
- Infection (most common)
- Stress, surgery, trauma
- New onset Type 1 DM

Clinical Features:
- Polyuria, polydipsia, dehydration
- Nausea, vomiting, abdominal pain
- Kussmaul respiration (deep, rapid breathing)
- Fruity (acetone) breath
- Confusion or coma in severe cases

Autonomic Neurotransmitters

1. Sympathetic Nervous System
- Preganglionic: Acetylcholine (ACh)
- Postganglionic: Mostly Norepinephrine (NE)
- Exception: Sweat glands use ACh
- Adrenal medulla: Releases Epinephrine and Norepinephrine into bloodstream

2. Parasympathetic Nervous System
- Preganglionic: Acetylcholine (ACh)
- Postganglionic: Acetylcholine (ACh)

Pituitary Gland – The Master Gland

• The pituitary gland is called the "master gland" because it controls the function of most other endocrine glands.
• It is a small pea-sized gland located at the base of the brain in the sella turcica of the sphenoid bone.
• It is connected to the hypothalamus via the infundibulum.

Parts of Pituitary Gland:
1. Anterior Pituitary (Adenohypophysis)
- Produces and secretes hormones like:
- Growth Hormone (GH)
- Thyroid Stimulating Hormone (TSH)
- Adrenocorticotropic Hormone (ACTH)
- Follicle Stimulating Hormone (FSH)
- Luteinizing Hormone (LH)
- Prolactin (PRL)

2. Posterior Pituitary (Neurohypophysis)
- Stores and releases hormones produced by the hypothalamus:
- Antidiuretic Hormone (ADH)
- Oxytocin

Classification of Lymphatic System 

1. Primary Lymphoid Organs
- Bone marrow: maturation of B cells
- Thymus: maturation of T cells

2. Secondary Lymphoid Organs
- Lymph nodes, spleen, MALT (tonsils, Peyer’s patches, appendix)

3. Lymphatic Vessels
- Begin as blind-ended capillaries
- Main ducts: thoracic duct, right lymphatic duct

4. Lymph
- Collected from interstitial fluid and returned to circulation