NEET MDS Synopsis
The Laryngopharynx
AnatomyThe Laryngopharynx
The laryngeal part of the pharynx lies posterior to the larynx.
It extends from the superior border of the epiglottis to the inferior border of the cricoid cartilage, where it narrows to become continuous with the oesophagus.
Posteriorly, the laryngopharynx is related to the bodies of C4 to C6 vertebrae.
Its posterior and lateral walls are formed by the middle and inferior constrictor muscles, with the palatopharyngeus and stylopharyngeus internally.
The laryngopharynx communicates with the larynx through the aditus or inlet of the larynx.
The piriform recess is a small, pear-shaped depression of the laryngopharyngeal cavity on each side of the inlet of the larynx.
Cells of the Nervous System
Pharmacology
Cells of the Nervous System
1-Neurons (Nerve Cells):function units of the nervous system by conducting nerve impulses, highly specialized and amitotic. Each has a cell body (soma), one or more dendrites, and a single axon.
• Cell Body: it has a nucleus with at least one nucleolus and many of the typical cytoplasmic organelles, but lacks centriolesfor cell division.
• Dendrites:Dendrites and axons are cytoplasmic extensions (or processes), that project from the cell body. They are sometimes referred to as fibers. Dendrites (afferent processes) increase their surface area to receive signals from other neurons, and transmit impulses to the neuron cell body.
• Axon: There is only one axon (efferent process) that projects from each cell body.
It carries impulses away from the cell body.
2-Glial cells: do not conduct nerve impulses, but support, nourish, and protect the neurons. They are mitotic, and far more numerous than neurons.
Astrocyte: A glialcell that provides support for neurons of the CNS, provides nutrients regulates the chemical composition of the extracellularfluid.
• Oligodendrocyte: A type of glialcell in the CNS that forms myelin sheaths.
• Microglia:The smallest glialcells; act as phagocytes (cleaning up debris) and protect the brain from invading microorganisms.
• Schwann cell:A cell in the PNS that is wrapped around a myelinatedaxon, providing one segment of its myelin sheath.
Cell, or Plasma, membrane
PhysiologyCell, or Plasma, membrane
Structure - 2 primary building blocks include
protein (about 60% of the membrane) and lipid, or
fat (about 40% of the membrane).
The primary lipid is called phospholipids, and molecules of phospholipid form a 'phospholipid bilayer' (two layers of phospholipid molecules). This bilayer forms because the two 'ends' of phospholipid molecules have very different characteristics: one end is polar (or hydrophilic) and one (the hydrocarbon tails below) is non-polar (or hydrophobic):
Functions include:
supporting and retaining the cytoplasm
being a selective barrier .
transport
communication (via receptors)
Assessing New Attachment in Periodontal Therapy
PeriodontologyAssessing New Attachment in Periodontal Therapy
Assessing new attachment following periodontal therapy is crucial for
evaluating treatment outcomes and understanding the healing process. However,
various methods of assessment have limitations that must be considered. This
lecture will discuss the reliability of different assessment methods for new
attachment, including periodontal probing, radiographic analysis, and histologic
methods.
1. Periodontal Probing
Assessment Method: Periodontal probing is commonly used
to measure probing depth and attachment levels before and after therapy.
Limitations:
Coronal Positioning of Probe Tip: After therapy,
when the inflammatory lesion is resolved, the probe tip may stop coronal
to the apical termination of the epithelium. This can lead to misleading
interpretations of attachment gain.
Infrabony Defects: Following treatment of infrabony
defects, new bone may form so close to the tooth surface that the probe
cannot penetrate. This can result in a false impression of improved
attachment levels.
Interpretation of Results: A gain in probing
attachment level does not necessarily indicate a true gain of connective
tissue attachment. Instead, it may reflect improved health of the
surrounding tissues, which increases resistance to probe penetration.
2. Radiographic Analysis and Reentry Operations
Assessment Method: Radiographic analysis involves
comparing radiographs taken before and after therapy to evaluate changes in
bone levels. Reentry operations allow for direct inspection of the treated
area.
Limitations:
Bone Fill vs. New Attachment: While radiographs can
provide evidence of new bone formation (bone fill), they do not document
the formation of new root cementum or a new periodontal ligament.
Therefore, radiographic evidence alone cannot confirm the establishment
of new attachment.
3. Histologic Methods
Assessment Method: Histologic analysis involves
examining tissue samples under a microscope to assess the formation of new
attachment, including new cementum and periodontal ligament.
Advantages:
Validity: Histologic methods are considered the
only valid approach to assess the formation of new attachment
accurately.
Limitations:
Pre-Therapy Assessment: Accurate assessment of the
attachment level prior to therapy is essential for histologic analysis.
If the initial attachment level cannot be determined with certainty, it
may compromise the validity of the findings.
Glomerular filtration
Physiology
Glomerular filtration
Kidneys receive about 20% of cardiac output , this is called Renal Blood Flow (RBF) which is approximatley 1.1 L of blood. Plasma in this flow is about 625 ml . It is called Renal Plasma Flow (RPF) .
About 20 % of Plasma entering the glomerular capillaries is filtered into the Bowman`s capsule .
Glomerular filtration rate is about 125 ml/min ( which means 7.5 L/hr and thus 180 L/day) This means that the kidney filters about 180 liters of plasma every day.
The urine flow is about 1ml/min ( about 1.5 liter /day) This means that kidney reabsorbs about 178.5 liters every day .
Filtration occurs through the filtration unit , which includes :
1- endothelial cells of glomerular capillaries , which are fenestrated . Fenestrae are quite small so they prevent filtration of blood cells and most of plasma proteins .
2- Glomerular basement membrane : contains proteoglycan that is negatively charged and repels the negatively charged plasma proteins that may pass the fenestrae due to their small molecular weight like albumin . so the membrane plays an important role in impairing filtration of albumin .
3- Epithelial cells of Bowman`s capsule that have podocytes , which interdigitate to form slits .
Many forces drive the glomerular filtration , which are :
1- Hydrostatic pressure of the capillary blood , which favours filtration . It is about 55 mmHg .
2- Oncotic pressure of the plasma proteins in the glomerular capillary ( opposes filtration ) . It is about 30 mm Hg .
3- Hydrostatic pressure of the Bowman`s capsule , which also opposes filtration. It is about 15 mmHg .
The net pressure is as follows :
Hydrostatic pressure of glomerular capillaries - ( Oncotic pressure of glomerular capillaries + Hydrostatic pressure of the Bowman capsule):
55-(35+10)
=55-45
=10 mmHg .
Te glomerular filtration rate does not depend only on the net pressure , but also on an other value , known as filtration coefficient ( Kf) . The later depends on the surface area of the glomerular capillaries and the hydraulic conductivity of the glomerular capillaries.
Articulations and Movement
Anatomy
Articulations
Classified according to their structure, composition,and movability
• Fibrous joints-surfaces of bones almost in direct contact with limited movement
o Syndesmosis-two bones united by interosseous ligaments
o Sutures-serrated margins of bones united by a thin layer of fibrous tissue
o Gomphosis-insertion of a cone-shaped process into a socket
• Cartilaginous joints-no joint cavity and contiguous bones united by cartilage
o Synchondrosis-ends of two bones approximated by hyaline cartilage
o Symphyses-approximating bone surfaces connected by fibrocartilage
• Synovial joints-approximating bone surfaces covered with cartilage; may be separated by a disk; attached by ligaments
o Hinge-permits motion in one plane only
o Pivot-permits rotary movement in which a ring rotates around a central axis
o Saddle-opposing surfaces are convexconcave. allowing great freedom of motion
o Ball and socket - capable of movement in an infinite number of axes; rounded head of one bone moves in a cuplike cavity of the approximating bone
Bursae
• Sacs filled with synovial fluid that are present where tendons rub against bone or where skjn rubs across bone
• Some bursae communicate with a joint cavity
• Prominent bursae found at the elbow. hip, and knee'
Movements
• Gliding
o Simplest kind of motion in a joint
o Movement on a joint that does not involve any angular or rotary motions
• Flexion-decreases the angle formed by the union of two bones
• Extension-increases the angle formed by the union of two bones
• Abduction-occurs by moving part of the appendicular skeleton away from the median plane of the body
• Adduction-occurs by moving part of the appendicular skeleton toward the median plane of the body
• Circumduction
o Occurs in ball-and-socket joints
o Circumscribes the conic space of one bone by the other bone
• Rotation-turning on an axis without being displaced from that axis
Gingival Crevicular Fluid
PeriodontologyGingival Crevicular Fluid (GCF)
Gingival crevicular fluid is an inflammatory exudate found in the gingival
sulcus. It plays a significant role in periodontal health and disease.
A. Characteristics of GCF
Glucose Concentration: The glucose concentration in GCF
is 3-4 times greater than that in serum, indicating
increased metabolic activity in inflamed tissues.
Protein Content: The total protein content of GCF is
much less than that of serum, reflecting its role as an inflammatory
exudate.
Inflammatory Nature: GCF is present in clinically
normal sulci due to the constant low-grade inflammation of the gingiva.
B. Drugs Excreted Through GCF
Tetracyclines and Metronidazole: These antibiotics are
known to be excreted through GCF, making them effective for localized
periodontal therapy.
C. Collection Methods for GCF
GCF can be collected using various techniques, including:
Absorbing Paper Strips/Blotter/Periopaper: These strips
absorb fluid from the sulcus and are commonly used for GCF collection.
Twisted Threads: Placing twisted threads around and
into the sulcus can help collect GCF.
Micropipettes: These can be used for precise collection
of GCF in research settings.
Intra-Crevicular Washings: Flushing the sulcus with a
saline solution can help collect GCF for analysis.
CELL ORGANELLES
General Microbiology
CELLS ORGANELLES
Cell parts:
Mitochondrion – double MB structure responsible for cellular metabolism – powerhouse of the cell
Nucleus – controls synthetic activities and stores genetic information
Ribosome – site of mRNA attachment and amino acid assembly, protein synthesis
Endoplasmic reticulum – functions in intracellular transportation
Gogli apparatus/complex – composed of membranous sacs – involved in production of large CHO molecules & lysosomes
Lysosome – organelle contains hydrolytic enzymes necessary for intracellular digestion
Membrane bag containing digestive enzymes
Cellular food digestion – lysosome MB fuses w/ MB of food vacuole & squirts the enzymes inside. Digested food diffuses through the vacuole MB to enter the cell to be used for energy or growth. Lysosome MB keeps the cell iself from being digested
-Involved mostly in cells that like to phagocytose
-Involved in autolytic and digestive processes
-Formed when the Golgi complex packages up an especially large vesicle of digestive enzyme proteins
Phagosome
– vesicle that forms around a particle (bacterial or other) w/in the phagocyte that engulfed it
- Then separates from the cell membrane bag & fuses w/ lysozome to receive contents
- This coupling forms phagolysosomes in which digestion of the engulfed particle occurs
Microbodies:
- Contain catalase
- Bounded by a single membrane bag
- Compartments specialized for specific metabolic pathways
- Similar in function to lysosomes, but are smaller & isolate metabolic reactions involving H2O2
- Two general families:
· Peroxisomes: transfer H2 to O2, producing H2O2 – generally not found in plants
· Glyoxysomes: common in fat-storing tissues of the germinating seeds of plants
¨ Contain enzymes that convert fats to sugar to make the energy stored in the oils of the seed available
Inclusions
– transitory, non-living metabolic byproducts found in the cytoplasm of the cell
- May appear as fat droplets, CHO accumulations, or engulfed foreign matter.