Self-Harm (cutting) Anatomy knowledge!
Subject #3: Veins & Nerves
Veins VS Nerves simplified
Nerves and veins are fundamentally different in their function and the system they belong to: nerves are part of the nervous system and transmit electrical signals, while veins are part of the circulatory system and carry deoxygenated blood. Nerves function like "electrical wires" to send messages to and from the brain, whereas veins act as "pipelines" to return blood to the heart.
To put it simply, veins are blood vessels that form a network of tubes throughout the body, carrying oxygen-poor blood back to the heart. They work with the heart and other blood vessels to keep blood circulating.
Detailed Vein information:
Size: Veins range in size from 1 mm to 2 cm, similar to a pencil point or quarter.
Blood type: Veins carry deoxygenated blood, except for the four pulmonary veins that carry oxygen-rich blood from the lungs to the heart.
Structure: Veins have thin walls and large, irregular lumens. Many veins have valves to prevent blood from flowing backward.
Location: Veins can be superficial, located in the fatty layer under the skin, or deep, located in the muscles and along bones. Connecting veins link the two.
Function: Veins in the legs fight gravity to push blood back to the heart. Deep veins contain 90% or more of the blood in the legs and are squeezed by surrounding muscles to help force blood toward the heart.
Valves: Found in many veins, especially in arms and legs, these one-way flaps ensure blood moves toward the heart, not backward, in low-pressure systems.
A vein has three main layers (tunics)
the inner Tunica Intima (endothelium for smooth flow), the middle Tunica Media (thin smooth muscle for slight constriction), and the thick outer Tunica Externa/Adventitia (connective tissue for structure and support), with veins often featuring internal one-way valves to prevent blood backflow, especially in limbs — according to this article here
What to expect if you cut a vein (how to know if you did or not)
If a vein is cut, you can expect steady, dark red bleeding and, depending on the severity, potential complications like significant blood loss and infection. It is a medical situation that requires prompt first aid and often professional medical evaluation.
Characteristics of Venous Bleeding
Blood Color: The blood is typically dark red or maroon because veins carry deoxygenated blood back to the heart.
Flow Pattern: The blood flows steadily or oozes from the wound. It does not spurt or pulse in rhythm with the heartbeat, as arterial blood does, because the pressure within veins is much lower than in arteries.
Severity: While often easier to control than arterial bleeding, cutting a large or deep vein can lead to substantial blood loss and is a potentially life-threatening emergency if not addressed immediately.
Untreated or severe venous bleeding can lead to complications, including:
Significant Blood Loss: Can result in hypovolemic shock (where the body loses too much blood) and potentially death.
Infection: Any open wound has a risk of infection, which requires proper medical cleaning and potentially antibiotics.
Tissue Damage: Persistent blood pooling around a damaged vein can cause damage to surrounding tissues.
Blood Clots: Damage to a vein can increase the risk of blood clots forming, such as deep vein thrombosis (DVT), which can become life-threatening if a clot travels to the lungs (pulmonary embolism).
Immediate Steps and First Aid
If you or someone else has a cut vein, the following first aid measures should be applied immediately:
Apply Direct Pressure: Place a clean cloth or sterile dressing directly over the wound and press down firmly. Continuous pressure helps slow the bleeding and encourages clotting.
Elevate the Injured Area: If the wound is on a limb, raise it above the level of the heart to help reduce blood flow to the area.
Monitor for Shock: Watch for signs of shock, which can include pale skin, dizziness, confusion, or a rapid heartbeat. If these symptoms appear, lay the person down and elevate their legs slightly (unless it causes pain).
Do Not Remove Embedded Objects: If an object is embedded in the wound, leave it in place and apply pressure around it. Removing the object could worsen the injury and increase blood loss.
Seek Medical Help Immediately: Call emergency services or a healthcare professional if the bleeding does not stop after 10-15 minutes of firm, direct pressure, if the wound is deep or large, or if the injured person shows signs of shock.
"What if I can't get medical help (right away)?"
If you cut a vein and can't get immediate medical help, apply firm, continuous direct pressure with a clean cloth/gauze, elevate the limb (if possible), and call emergency services (911) if bleeding is severe or won't stop after 10 minutes; use a tourniquet only as a last resort for severe limb bleeding if trained, but don't use improvised ones. Control the flow until professional help arrives, but do not remove soaked bandages, just add more layers on top to maintain pressure.
Nerves in the body are a vast communication network, like electrical wires, connecting the brain and spinal cord (Central Nervous System - CNS) to the rest of the body (Peripheral Nervous System - PNS), transmitting sensory info in and motor commands out, controlling movement, sensation, and vital functions, with trillions of fibers forming hundreds of named nerves (like cranial & spinal) and nerve plexuses (e.g., brachial, sciatic). They are bundles of neurons (nerve cells) with axons that carry electrical signals (action potentials) rapidly, insulated by myelin for efficiency.
Sensory (Afferent) Nerves: Carry messages to the brain/CNS from your senses (touch, sight, sound) and body.
Motor (Efferent) Nerves: Carry commands from the brain/CNS to muscles and glands.
Mixed Nerves: Contain both sensory and motor fibers.
Main Divisions & Examples
Cranial Nerves (12 pairs): Emerge from the brain, controlling head, neck, face (e.g., Optic, Facial, Vagus nerves).
Spinal Nerves (31 pairs): Branch from the spinal cord, serving the body (e.g., Radial nerve in arm, Sciatic nerve in leg).
Nerve Plexuses: Where spinal nerves mix and recombine to serve specific areas (e.g., Brachial plexus for arms).
Signal Generation: Neurons receive stimuli (light, touch, pain) via dendrites.
Transmission: Signals (action potentials) travel down axons, insulated by myelin for speed.
Connection: Signals jump synapses to other neurons, eventually reaching the brain.
Response: The brain processes info and sends commands back via motor nerves to act.
Axons: Long nerve fibers (extensions of neurons) that carry impulses.
Myelin Sheath: Fatty insulation for faster signals; damage slows or stops signals.
Bundles: Axons are bundled into fascicles, and these bundles form the nerve, wrapped in connective tissues (endo-, peri-, epineurium).
What to expect if you cut a nerve
If you cut a nerve, you can expect immediate loss of feeling (numbness) or muscle control (weakness/paralysis) in the affected area, plus potential pain, tingling, or burning, as signals can't pass through the break.
Recovery involves slow nerve regrowth (about 1mm/day) and often requires surgical repair to reconnect ends, preventing painful nerve balls (neuromas) and restoring function, though full recovery can take months to years and depends heavily on the injury's severity.
Immediate & Short-Term Effects
Sensory Loss: Numbness, tingling, buzzing, or loss of touch, temperature, and pain sensation.
Motor Loss: Weakness, twitching, or complete inability to move muscles controlled by that nerve (e.g., dropping things).
Pain: Can occur at the injury site or along the nerve's path, sometimes feeling like electric shocks.
Skin Changes: Skin might become dry, change color, or have altered texture.
What Happens Inside the Nerve
A cut creates a gap, stopping signals like a severed electrical wire.The nerve end farthest from the brain dies back, while the part connected to the brain stays alive.
Without repair, nerve fibers try to grow but often form a painful ball called a neuroma
Surgical Repair: Often necessary to suture or bridge the nerve ends, allowing fibers to grow down the correct path.
Slow Growth: Nerves regrow slowly (about 1mm/day or 1 inch/month), so healing takes a long time.
Physical Therapy: Helps prevent stiffness and restore movement.
Medication: Pain relievers or specific nerve pain medications may be used.
What to do if you cut a nerve
If you cut a nerve, seek immediate medical attention (ER/Urgent Care) for deep cuts as surgery (direct repair, graft, or conduit) is often needed, especially in hands, to restore function by reattaching nerve ends or bridging gaps, with physical therapy crucial for recovery; for minor cuts, keep it clean and monitor, but numbness, tingling, or weakness signals nerve involvement needing prompt assessment
For Deep Cuts (Seek Urgent Care/ER)
Get Help Fast: The sooner nerve repair happens, the better the chance of full function, especially in fingers.
Initial Care: Clean the wound gently, apply pressure to stop bleeding, and elevate the area if possible.
Treatment Options: A surgeon might stitch the nerve ends directly (direct repair), use a nerve graft from another body part, or use a synthetic tube (conduit) to bridge the gap.
For Minor Cuts (Monitor Closely)
Signs of Nerve Injury: Tingling, numbness, weakness, or inability to move the area properly.
Home Care: Keep it clean and dry, use ice to reduce swelling, and elevate it.
When to See a Doctor: If symptoms persist or worsen, see a doctor to rule out nerve damage
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The first image explains the nervous system, and gives us a relatively accurate depiction of where the nerves are located.
The second image gives us the names of different veins and shows us where each are located, and where they connect to.
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Google
How do nerves and veins differ?
How to tell when it's venous bleeding
Peripheral nerve injuries
Nerves
@landmineblr (tagging you again!!)