Anatomy

Reference: Langman’s 13th; P-54

Post-translational Modification of Protein Occurs in:
1. Golgi apparatus
2. Ribosome
3. RER

Organelles Involved in Protein Synthesis:
1. Ribosome
2. RER
3. Mitochondria

Spinal cord gives rise to 31 pairs of spinal nerves

Microvilli is concerned with absorption.

Tributaries of azygos vein: 
1. Right superior intercostal vein (formed by union of the 2nd, 3rd 4th posterior intercostal veins)
2. 5th-11th right posterior intercostal veins
3. Hemiazygos vein (at the level of lower border of T 8
4. Accessory hemiazygos vein (at the level of upper border of T 8
5. Right bronchial vein
6. Several oesophageal mediastinal, pericardial veins
7. Formative tributaries: Right subcostal & right ascending lumbar vein

Gap junctions abundant in Muscular tissue

*** Collecting part of the kidney (From collecting tubules up to urethra) develops from the ureteric bud (i.e. mesonephric duct)
*** Secretory part of kidney (Nephron) develops from metanephros.


Derivatives of mesonephric duct: 
a. Ureteric bud: It gives rise to collecting part of the kidney-
   • Collecting tubule & collecting duct
   • Minor calyx
   • Major calyx
   • Renal pelvis
   • Ureter
b. Trigone of urinary bladder
c. Male genital ducts:
   • Prostate & part of prostatic urethra
   • Seminal vesicle
   • Epididymis
   • Vas deferens
   • Ejaculatory duct

Explanation-
Spleen, Pancreas, Stomach-related to left kidney

Negative pressure (suction) causes the visceral pleura to remain in contact with the parietal pleura, so that when the chest wall & parietal pleura move, the parietal pleura takes the visceral pleura and lungs with it.

Reference: Junqueira’s Basic Histology; 14th Edition; Page-236

Adrenal Medullary parenchymal cells, known as chromaffin cells, arise from neural crest cells, as do the postganglionic neurons of sympathetic and parasympathetic ganglia. Chromaffin cells can be considered modified sympathetic postganglionic neurons, lacking axons and dendrites and specialized as secretory cells.

Mitochondria are membrane enclosed organelles with arrays of enzymes specialized for aerobic respiration and production of ATPs. Hence it is called the power house of cell.

- Size: 0.5-1 um in diameter & up to 10 um in length

- Shape: Elongated/rod shaped

- Number: The number of mitochondria is related to the cell's energy needs: cells with a high- energy metabolism (eg, cardiac muscle, cells of some kidney tubules, hepatocytes etc.) have abundant mitochondria, whereas cells with a low-energy metabolism have few mitochondria.

- Mitochondria are absent in RBCs and terminal keratinocytes of skin.

- Mitochondrial matrix contains a small circular chromosome of DNA, ribosomes, mRNA, and tRNA, all with similarities to the corresponding bacterial components.

- Mitochondrial DNA is a small circular double helix DNA that contains 37 genes.
- Mitochondrial DNA is inherited from mother (ovum), as cytoplasm of sperm do not contribute to zygote.
- Due to mitochondrial DNA, mitochondria are self replicating.

- Mitochondria are highly plastic, rapidly changing shape, fusing with one another and dividing, and are moved through the cytoplasm along microtubules.

Sympathetic Nerve supply of appendix arise from T10

Barr body:
- Tightly coiled clump of chromatin mass (heterochromatin), genetically inactive
- It represents inactivated X chromosome.**
- During cell division Barr body disappears
- Number of Barr body is always 1 less than the number of X chromosome
- Female has 1 Barr body, male has no Barr body normally.
- Klinefilter syndrome : 47,XXY ; 1 Barr body

*** There is no male to male transmission in X-linked disorders, because in male the X chromosome comes from the mother. 

Criteria of X-linked recessive disorders:
1. Affected cases are usually males carrying the gene.
2. Homozygous females can be affected, but this is rare. 
3. Heterozygous females usually do not express the full phenotypic changes because of the paired normal allele.
4. Only females are carriers.
5. If a female has the allele (female carrier)- with a normal male, off-springs will be-
    - 50% daughters carrier, 50% normal
    - 50% sons affected, 50% normal
6. If a male has the allele (affected male)- with a normal male the off-springs will be-
    - All daughters carrier
    - All sons normal (no male to male transmission)
7. Affected cases have affected brothers and maternal uncles.
8. Since females have two copies of X-chromosomes and males have only one, X-linked recessive disease are much more common among males than in females.

Periosteum is a layer of dense connective tissue on the outer surface of bone, bound to bone matrix by bundles of type I collagen called perforating (or Sharpey) fibers.

Reference: Langman’s 13th; P-32

The genetic code is a series of codons by which DNA directs transcription of RNA and its translation into proteins

Properties of genetic code:
 Specificity
 Universality
 Redundant (degenerate)
 Non-overlapping
 Comma less

Reference: Junqueira’s Basic Histology; 14th Edition; Page-438

Median nerve is injured above the level of the elbow in supracondylar fracture of the humerus. As a result, Ape or monkey thumb deformity is present due to paralysis of the thenar muscles.

Intramembranous ossification, by which most flat bones begin to form, takes place within condensed sheets (“membranes”) of embryonic mesenchymal tissue. Most bones of the skull and jaws, as well as the scapula and clavicle, are formed embryonically by intramembranous ossification.

The left upper lobe contains the cardiac notch, where the left ventricle and pericardial sac lodges. The Lingula (which is the embryologic counterpart to the right middle lobe) lies just beneath the cardiac notch.

The. Content of space of Disse is kupffer cell.

The hypothalamic hypophyseal tract includes bundles of nerve axons that run from supraoptic nucleus (SON) and paraventricular nucleus (PVN) in the hypothalamus to the posterior pituitary.

Membranous part is the shortest part of male urethra

Hemophilia- X-linked recessive
Myotonic dystrophy, Osteogenesis imperfecta- Autosomal dominant

Examples of autosomal recessive disorders: 

Metabolic:
1. Homocystinuria/Alpha-1 antitrypsin deficiency
2. Cystic fibrosis
3. Phenylketonuria
4. Alkaptonuria
5. Wilson’s disease
6. Galactosemia
7. Lysosomal storage disease
8. Glycogen storage disease

Haematopoietic:
1. Thalassaemia
2. Sickle cell anaemia

Endocrine:
1. Congenital adrenal hyperplasia

Nervous: 
1. Neurogenic muscular atrophy
2. Friedrich’s ataxia
3. Spinal muscular atrophy

Skeletal: 
1. Some variants of Ehlers-Danlos syndrome

Gastrulation is an event of 3rd week of development.

Filiform papillae: They are the most numerous papillae. They are small and conical in shape. The epithelium at the tips of these papillae is keratinised. It may project in the form of threads.

Common sites for peptic ulcers are the first part of the duodenum and the lesser curve of the stomach, but they also occur on the stoma following gastric surgery, in the oesophagus and even in a Meckel’s diverticulum, which contains ectopic gastric epithelium. In general, the ulcer occurs at a junction between diferent types of epithelia, in the epithelium least resistant to acid damage.

The beating of the cilia moves mucus lying on the surface of the epithelium of the conducting zone, and any contained dust, up out of the bronchial tree.

Retrocecal is most common(65%) position of appendix.

Oculomotor, Abducent & ophthalmic nerve passes through Superior orbital fissure

An unpaired median sacral artery arises posteriorly at the level of L4 to supply the coccyx, lumbar vertebrae and the sacrum.