Question 1. Intraembryonic mesoderm.

Answer:

• The embryonic disc is made up of three germ layers – ectoderm, mesoderm and endoderm.
• The mesoderm layer present within the embryonic disc is known as intra – embryonic mesoderm.
• It spreads throughout the disc except in the region of the prochordal plate,
• It shows three subdivision.
  1. Paraxial mesoderm.
     • It is the mesoderm next to the middle line.
     • It undergoes segmentation to form somites.
  2. Later plate mesoderm.
     • Lateral plate mesoderm.
     • It contains intra-embryonic coelem.
  3. Intermediate mesoderm.
     • It is a strip of mesoderm present between the lateral plate mesoderm and the paraxial mesoderm.

• Time of formation: 19 days of IU life.

Question 2. Fertilization
Answer:

• It is the process by which male and female gametes fuse
• It occurs in the ampullary region of the uterine tube

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Question 1. Turner’s syndrome.
Answer:

Turner’s syndrome. Causes: Monosomy of sex chromosome.

Turner’s syndrome. Effects:

• Agenesis of ovaries
• Mental retardation
• Skeletal abnormalities
• Webbed neck.
• Short stature
• Lymphedema of the extremities
• Broad chest with widely space.

Question 2. Development of pituitary gland/Hypophysis cerebri.
Answer:

• Pituitary gland develops from the two separate sources.
  1. The anterior and intermediate parts develop from an ectodermal diverticulum (rathke’s pouch) that grows upwards from the roof of the stomadeum.
     • The anterior wall of Rathke’s pouch proliferates to form the pars anterior of the hypophysis.
     • The posterior wall remains thin and forms the pars intermedia.
  2. The pars nervosa and stalk of the hypophysis cereberi develop from a down growth from the floor of the third ventricle in the region of the infundibulum.
     • A small extension of this lobe, the pars tuberalis, grows along the stalk of the infundibulum and eventually surrounds it.
     • The posterior lobe of the hypophysis is composed from the hypothalamic area.

Question 3. Development of parathyroid gland.
Answer:

• In the fifth week embryo parathyroid gland develops.
• The inferior parathyroid gland [Parathyroid III] develops from endoderm of the third pharyngeal pouch.
• The superior parathyroid gland [Parathyroid IV] develops from endoderm of the fourth pharyngeal pouch.
• When the thymus descend toward the thorax, parathyroid III is carried along with it.
• But parathyroid IV is prevented from descending as it is closely related to thyroid gland.
• Thus parathyroid III becomes caudal to parathyroid IV.

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Hypocalcified structures of enamel
Answer:

1. Enamel lamellae
   • They extend for varying depths from the enamel surface
   • They are thin, leaf-like structures filled with organic material
   • They may develop in planes of tension
   • Types:
2. Type A
   • Consist of poorly calcified rod segments
   • Restricted to enamel
3. Type B
   • Consist of degenerated cells
   • They are restricted to the dentin
4. Type C
   • These fare lamellae arising in erupted teeth
   • They are restricted to the dentin
5. Enamel tufts
   • Enamel tufts are tuft structures arising from dentin-enamel junction towards the enamel surface
6. Enamel spindles
   • They are mesenchymal in origin.
   • They are formed by extensions of odontoblast processes into enamel before calcification.
7. Surface structures
   • Perikymata
     • The small ridges and perikymata seen on the surfaces of canines are a result of normal development.
     • They are shallow furrows on the enamel surfaces where the striae of Retzius end.
   • Rod ends
     • They are concave and vary in depth and shape
   • Cracks
     • They are narrow, fissure-like structures that are seen on almost all surfaces

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Question 1. Define isoenzymes. Name them & give their clinical importance (or) LDH Isoenzymes
Answer:

Definition Isoenzymes:

• Isoenzymes are the multiple forms of an enzyme catalyzing the same reaction

Isoenzymes Examples:

Question 2. Define competitive inhibition. Give three examples (or) Features & examples of competitive & feedback inhibitions.
Answer:

Competitive Inhibition Definition:

1. The inhibitor which is structurally similar to the tire substrate competes with the Ore substrate for the binding site.
2. This diverts the enzyme to form enzyme- inhibitor complex instead of an enzyme-substrate complex.
3. This complex does not produce any products & remains stable
4. It results in the prevention of further enzymatic activity.
5. This is known as competitive inhibition.

Competitive Inhibition Features:

• It can be reversed by adding an excess substrate which will dislodge the inhibitor molecules
• The action of drugs depends upon the inhibitor present

Competitive Inhibition Examples:

Feedback Inhibition:

• It is a specialized type of allosteric inhibition necessary to control metabolic pathways for efficient cellular functions.
• Example: Aspartate transcarboxylase, ATCase
• Carbamoyl phosphate undergoes a sequence of reactions for the synthesis of the end product cytidine triphosphate, CTP.
• When CTP accumulates, it allosterically inhibits the enzyme ATCase
• This is called feedback inhibition

The post Isoenzymes And Enzyme Regulation appeared first on BDS Notes.

Describe the following aspects of enzymes:

1. Specificity
2. Four factors influencing enzyme activity
3. Competitive enzyme inhibition.

Answer:

Enzymes Specificity:

• Enzymes are highly specific in their actions

Enzymes Types of specifically:

Factors influencing enzyme activity:

Competitive enzyme inhibition:

• The inhibitor which is structurally similar to the substrate competes with the substrate for the binding site.
• This diverts the enzyme to form an enzyme inhibitor complex instead of an enzyme-substrate complex.
• This complex does not produce any products and remains stable.
• It results in the prevention of further enzymatic activity.
• This is known as competitive inhibition.
• It can be reversed by adding an excess of the substrate which will dislodge the inhibitor.
• The action of drugs depends on the inhibitor present

Enzymes Examples:

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Question 1. Normal pH of the blood
Answer:

The normal pH of the blood is in the range of 7.35-7.45

Question 2. Metabolic & respiratory acidosis
Answer:

The post Metabolic Acidosis And Acid–Base Balance appeared first on BDS Notes.

Bite marks.
Answer:

• When the dentition of a human/animal impresses the surface of an object during the act of biting, a mark is imprinted called a bite mark.

Characteristics:

• It includes the size and shape of the pattern.
• It should be consistent with the dental arch size of the suspected biter.
• It retains a circular shape consisting of two half arches separated by a space i.e., a temporomandibular joint.
• One each should be larger representing the maxillary arch.
• Individual characteristics.
  1. Maxillary central incisor – large rectangle.
  2. Mandibular incisor and maxillary lateral incisor – small rectangle
  3. Cuspid – point or triangle
  4. Maxillary cuspid – figure eight pattern.
  5. Mandibular cuspid – point.
  6. Molar – not seen routinely.

Significance:

• It is used for forensic purposes.
• The pattern left by the teeth can be evaluated and compared to the dentition and suspected caused it.
• No two individuals have an identical dentition, thus, useful in forensic dentistry.

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Histology of Submandibular Gland
Answer:

• Submandibular gland is a mixed salivary gland
• It contains both serous and mucous acini
  1. Serous cells:
     • They are darkly stained
     • Have rounded nuclei placed towards the base
     • They are arranged in the form of rounded acini or roughly pyramid
     • Base is towards basement membrane and apex towards lumen
     • Apex shows microvilli and pinocytotic vesicles
     • Lumen has intercellular secretory canaliculi
     • Cytoplasm contains
     • Small and homogenous secretory granules Prominent Golgi apparatus
     • Abundant rough endoplasmic reticulum Mitochondria
     • Lysosomes
     • Microfilaments
  2. Mucous cells:
     • They are lightly stained
     • Nucleus is flattened and present towards the basement membrane
     • Cells are arranged in form of tubules
     • Cells lining the tubules are columnar
     • Secretory granules are large and ill defined
  3. Demilunes/Crescents:
     • These are mucous cells covered by serous cells
     • They are present at the ends of mucous tubules

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Histology of Suprarenal Gland
Answer:

• It is also called adrenal gland
• It is covered by connective tissue capsule
• Septa extends from capsule and divides the gland substance

Histology of Suprarenal Gland Parts:

1. Cortex:
   • It is made up of cells arranged in cords
   • Sinusoids intervene between the cords
   • Layers:
     1. Zona glomerulosa
        • Outermost layer
        • Consists 1/5th of cortex
        • Cells are arranged as inverted U shape
     2. Zona fasciculata
        • Cells are arrange in straight columns
        • Sinusoids intervene between columns
        • Consists 3/5th of cortex
     3. Zona reticularis
        • Consists 1/5th of cortex
        • Made up of cords that branch and anastomose

• • Secretions:

1. • • Aldosterone and deoxycorticosterone by cells of zona glomerulosa
     • Cortisone and cortisol by cells of zona fasciculata
     • Glucocorticoids and sex hormones by cells of zona reticularis
2. Medulla:
   • Cells shows yellow cytoplasm
   • Cells are columnar
   • Arranged in columns which are separated by wide sinusoids
   • Cytoplasm is basophilic
   • Secretions:
   • Secretes adrenaline and non adrenaline

The post Suprarenal Gland Structure Under The Microscope: Cortex, Medulla, And Sinusoids appeared first on BDS Notes.

Histology of Thymus
Answer:

• Thymus consists of right & left lobes joined by fibrous tissue
• Each lobe is about 2 mm in diameter
• It has outer cortex & inner medulla
• Each lobe has
  1. Capsule
     • Made up of connective tissue
  2. Septa
     • It passes from capsule which incompletely divides the lobe into lobules

Cells of Thymus:

1. Epithelial cells called epitheliocytes
   • They are flattened cells
   • They join to form sheets covering internal surface of capsule, surfaces of septa & surfaces of blood vessels
   • They lie deep in the lobule
     Functions:
   • Prevents antigen present in blood from reaching lymphocytes in thymus
   • Promotes Tcell differentiation & proliferation

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