The external and internal laryngeal nerves :difference between

 

The external and internal laryngeal nerves are branches of the superior laryngeal nerve which is the branch of  vagus nerve (CN X).

1. Location of these nerves

• External Laryngeal Nerve branch of superior laryngeal nerve
• Descends alongside the superior thyroid artery.
• It runs along the external surface of  the larynx, related to the the thyrohyoid membrane.
• It is supplied  the cricothyroid muscle.
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• Internal Laryngeal Nerve branch of superior laryngeal nerve
• The internal laryngeal nerve (internal branch of the superior laryngeal nerve) descends to the thyrohyoid membrane, piercing it alongside the superior laryngeal artery. It provides sensory innervation to the epiglottis, base of the tongue, epiglottic glands, aryepiglottic folds, and laryngeal mucosa down to the vocal folds.

2. Relation

• External Laryngeal Nerve : near to  the superior thyroid artery, which makes it vulnerable during thyroid surgery. It is situated outside the larynx, and related  to the inferior constrictor muscle.
• Internal Laryngeal Nerve : it is run with the superior laryngeal artery and pierce the thyrohyoid membrane. It is located deep to the laryngeal mucosa,  the aryepiglottic folds and epiglottis.
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3. Function

• External Laryngeal Nerve
• Motor function: Supplies the cricothyroid muscle, which tenses the vocal cords and modulates pitch of voice.
• Clinical significance: Damage of this nerve leads to a monotonous voice (no up or down of speech) due to loss of high-pitched sounds.
• Internal Laryngeal Nerve
• Sensory function: it gives sensation to the mucosa of the larynx above the vocal cords, including the epiglottis and piriform recess.
• Clinical significance: Damage of this nerve causes loss of cough reflex, leading to aspiration of food or fluid within the larynx.

 

Concise difference between external and internal laryngeal nerve

Feature	External Laryngeal Nerve	Internal Laryngeal Nerve
Origin	Superior laryngeal nerve (CN X)	Superior laryngeal nerve (CN X)
Course	Runs along the superior thyroid artery	Pierces the thyrohyoid membrane
Relation	It is closely related   to superior thyroid artery which is the branch of external carotid artery , outside larynx	It runs with  superior laryngeal artery which is the branch of superior thyroid artery ,  inside larynx
Function	Motor: innervate Cricothyroid muscle (pitch control)	Sensory: it gives sensory supply to the mucosa above vocal cords (cough reflex)
Damage Effect	No voice loss but monotonous voice (no high pitch)	Loss of sensation, risk of aspiration of food or fluid within the larynx

biomechanical difference between males and females related to the angle of the femur and its impact on running speed

 biomechanical difference between males and females related to the angle of the femur and its impact on running speed. Let's break down the vector math and the biomechanical forces involved.

1. Q-Angle (Quadriceps Angle):  Q-angle is the angle formed between the line of the quadriceps muscles (the force vector generated by the thigh muscles) and the patella tendon (which acts to extend the knee).

   • In females, the Q-angle is generally larger due to the wider pelvis. This means that the femur (thigh bone) is more oblique in females, creating a greater angle relative to the tibia (shin bone).
   • In males, the Q-angle is smaller because their pelvis is narrower and their femur is more aligned with the tibia, making the angle between the femur and tibia closer to 90 degrees.

2. Effect of the Oblique Femur (in females) on Force Transmission:

   • The oblique orientation of the femur in females affects how the forces generated by the quadriceps muscles are transmitted through the leg.
   • Since the force vector from the quadriceps (generated by the femur) is angled more laterally in females, it doesn't pass through the tibia in a straight line. Instead, the force is distributed at an angle, which results in less efficient force transmission to the ground.
   • In males, where the femur is more straight and aligned with the tibia, the force generated by the quadriceps can be transmitted more directly through the tibia to the ground, making force generation more efficient.

3. Impact on Running Mechanics:

   • The efficiency of force application is crucial for running speed. The more direct and aligned the force is, the greater the propulsion during running.
   • In females, due to the larger Q-angle, the obliquely aligned femur leads to less efficient force transfer from the hip to the knee and then to the foot. This misalignment results in greater energy loss, which ultimately contributes to slower speeds.

4. Biomechanics of Females vs Males:

   • Because the femur is more oblique in females, the muscle forces (generated by the quadriceps) are not applied as efficiently to the ground compared to males. This reduces the overall propulsive force females can generate with each step.
   • Males, with their more aligned femur, have a more efficient transfer of forces through the body, which allows them to generate more forceful pushes during each stride, aiding in faster running speeds.

Vector Math and Force Distribution:

1. Force Vectors:

   • The force vector generated by the quadriceps (which extends the knee) must travel through the femur and tibia to be applied to the ground. In females, due to the larger Q-angle, this vector becomes less direct and needs to be resolved into multiple components.
   • The result is that a portion of the generated force goes into lateral or sideways motion, and less force is directed into forward motion, reducing running efficiency.

2. Work Done by Muscles:

   • The work done by muscles (force × distance) is less efficient in females, particularly in terms of forward propulsion, due to the misalignment of forces. This leads to slower running speeds since more energy is lost in lateral movements and inefficiencies.

Conclusion:

The larger Q-angle and the oblique femur in females contribute to a less efficient force transmission during walking and running. Due to the angled position of the femur, the force vector from the quadriceps is not directly aligned with the tibia, leading to less effective propulsion and slower speeds. Males, with a more aligned femur, can apply their muscle forces more efficiently, resulting in faster running speeds. This biomechanical difference is a significant factor in why females may generally run slower than males.

Wagenworth's Index and Kernohan's Index of umbilical cord

 Wagenworth's Index and Kernohan's Index of umbilical cord 

These terms are not widely documented in standard medical literature related to the umbilical cord. However, based on similar indices used in umbilical cord assessment,

1. Wagenworth Index – it is an index that  related to umbilical cord coiling or vascular resistance, possibly indicating the degree of spirality or torsion of the umbilical cord. A decreased index may suggest hypocoiling, which has been associated with fetal distress, intrauterine growth restriction (IUGR), and adverse pregnancy outcomes.

2. Kernohan Index – it is  a measurement related to vascular flow resistance or umbilical artery Doppler indices. A decrease in Kernohan Index might indicate poor perfusion in the umbilical cord, which could be linked to conditions like preeclampsia, fetal hypoxia, or placental insufficiency.

Myth or Reality: The Umbilical Cord is Full of Stem Cells?

Myth or Reality: The Umbilical Cord is Full of Stem Cells?

Reality: The umbilical cord contains a mix of cell types, not just stem cells.

• Cord blood contains hematopoietic stem cells (HSCs), which contribute to blood cell formation. It also includes:

  • Red blood cells (carry oxygen)
  • White blood cells (fight infections)
  • Platelets (facilitate clotting)

• Cord tissue contains multiple types of mesenchymal stem cells (MSCs), found in:

  • The lining of the cord
  • The lining of blood vessels
  • Wharton’s jelly (the protective gel-like substance around blood vessels)

Umbilical vessels (both umbilical arteries & umbilical vein) do not have vasa vasorum why ?

 Umbilical vessels (both umbilical arteries & umbilical vein) do not have vasa vasorum because:

1. Thin Vessel Walls – The umbilical vessels, especially umbilical vein, have  thin walls compared to large systemic vessels, reducing  need for additional blood supply.

2. High Oxygenation in Umbilical Vein – The umbilical vein carries oxygenated blood from the placenta, meaning its wall is already well-supplied with oxygen &  nutrients from its lumen.

3. Short Functional Duration – The umbilical vessels are temporary structures, functioning only during fetal life. Since they are not long-term vessels, they do not develop complex vascular support systems like vasa vasorum.

4. Surrounding Wharton's Jelly – The umbilical vessels are embedded in Wharton’s jelly, a gelatinous connective tissue that protects them from external compression and maintains their patency, reducing the need for additional microvasculature.

5. Lower Wall Metabolic Demand – Unlike large systemic arteries like the aorta, which have thick muscular and elastic walls requiring extra nourishment, the umbilical vessels have a relatively lower metabolic demand, making vasa vasorum unnecessary.

In contrast, large systemic vessels such as the aorta require vasa vasorum to supply nutrients and oxygen to their thick walls, particularly in the outer layers where diffusion from the lumen is insufficient.

Norma verticalis

 The norma verticalis refers to the vertical view of the skull, often used in anatomical studies and radiology. This view looks at the skull from above and provides insight into the superior and lateral aspects of the cranium. Here's a brief overview:

Key Features of Norma Verticalis:

1. Cranial Vault: Includes the calvaria (the dome-like top part of the skull), which is formed by the frontal, parietal, and occipital bones.
2. Parietal Bones: These are the paired bones on the sides and top of the skull, visible in this view.
3. Frontal Bone: The bone forming the forehead.
4. Occipital Bone: The bone forming the back and base of the skull.
5. Sagittal Suture: The joint that connects the two parietal bones along the top of the skull.
6. Coronal Suture: The joint that connects the frontal bone to the parietal bones, running horizontally from side to side.

Significance:

• The norma verticalis helps in understanding the overall shape of the skull, the symmetry of cranial structures, and the alignment of the bones from a top-down perspective. It’s particularly useful for studying skull deformities, cranial surgery, and radiological imaging.
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Anatomy of orbital cavity with video

 The orbital cavity (or eye socket) is  bony structure that houses and protects  eyeball & its associated structures. The walls of orbital cavity are formed by seven different bones, which are:

1. Roof of  Orbit (Superior Wall)

   • Bone(s): orbital plates of Frontal bone
   • Description: The roof is formed by the orbital part of the frontal bone. It provides the upper boundary of the orbit and helps protect the eye from above.

2. Floor of the Orbit (Inferior Wall)

   • Bone(s): Maxilla, zygomatic bone, and palatine bone
   • Description: The floor of  orbit is mainly formed by  maxilla and a portion of  zygomatic bone. The palatine bone also contributes slightly at the posterior part. This wall supports the lower part of the eye.

3. Medial Wall of the Orbit

   • Bone(s): Maxilla, lacrimal bone, ethmoid bone, and part of the sphenoid bone
   • Description: The medial wall is formed by the maxilla, lacrimal bone, ethmoid bone (specifically the lamina papyracea), and a small portion of  sphenoid bone. It is the thinnest of the orbital walls and separates the orbit from  nasal cavity.

4. Lateral Wall of the Orbit

   • Bone(s): Zygomatic bone & greater wing of  sphenoid bone
   • Description: The lateral wall is formed by  zygomatic bone and  greater wing of  sphenoid bone. It is  thickest of  orbital walls, providing strength & protection to  side of  eye.

5. Posterior Wall of the Orbit

   • Bone(s): Sphenoid bone (specifically the lesser wing and body)
   • Description: The posterior wall is formed primarily by  sphenoid bone. It serves as  back portion of the orbit & contains the optic foramen (or canal) through which optic nerve passes.
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