Human Anatomy: Muscle Tissue, Muscular System, Blood, Heart, Vessels, and Lymphatic System

Comprehensive Question and Answer flashcards covering human muscle tissue, body muscles, blood composition, heart anatomy and physiology, vascular circulation, and the lymphatic system.

What are the four unique characteristics of muscle tissue?

Excitability (responds to stimuli), contractility (able to shorten), elasticity (ability to rebound), and extensibility (ability to stretch and still contract).

What are the three connective tissue layers surrounding skeletal muscle structural components?

Endomysium (surrounds each individual muscle fiber), perimysium (surrounds bundles of muscle fibers called fascicles), and epimysium (surrounds the entire skeletal muscle).

What is deep fascia and its primary function?

Deep fascia is an expansive sheet of dense irregular connective tissue that separates individual muscles and binds together muscles with similar functions.

How do origin and insertion differ regarding skeletal muscle attachments?

The origin is the less movable attachment of a muscle (typically lying proximal), whereas the insertion is the more movable attachment that is pulled toward the origin during contraction.

What components constitute a motor unit?

A motor unit is composed of a single motor neuron, the muscle fibers it controls, and the neuromuscular junctions between the motor neuron and muscle fibers.

What is the All-Or-None Principle of muscle fiber contraction?

It states that a muscle fiber either contracts completely or does not contract at all.

What is the functional contractile unit of a skeletal muscle fiber, and how is it defined structurally?

The sarcomere is the functional contractile unit of a skeletal muscle fiber, defined as the distance from one Z disc to the next adjacent Z disc.

In skeletal muscle striations, what do the A bands and I bands contain?

The dark bands (A bands) contain the entire thick filament, while the light bands (I bands) contain thin filaments only.

How do isometric and isotonic muscle contractions differ?

In isometric contraction, muscle tension is less than resistance so muscle does not shorten and no movement occurs; in isotonic contraction, muscle tension exceeds resistance, causing the muscle to shorten and movement to occur.

What are the three types of skeletal muscle fibers and their relative fatigue resistance?

Fast fibers (fast contraction, fatigue rapidly), Intermediate fibers (slower than fast but faster than slow, greater fatigue resistance), and Slow fibers (slow to contract and fatigue, containing large numbers of mitochondria).

What are the four organizational patterns of muscle fascicles?

Circular (sphincter pattern), Convergent (muscle fibers converge on a common attachment site), Parallel (fascicles run parallel to long axis with a central belly), and Pennate (Unipennate, Bipennate, and Multipennate).

How are skeletal muscle functional roles categorized into agonists, antagonists, synergists, and fixators?

Agonists (prime movers) contract to produce movement, antagonists oppose the agonist's action, synergists assist the prime mover, and fixators prevent movement at a joint to stabilize the origin of the agonist.

What structural features distinguish cardiac muscle from skeletal muscle?

Cardiac muscle fibers are short, Y-shaped branching, striated with 1-2 nuclei per cell, joined by intercalated discs, and contain autorhythmic cells capable of generating impulses without nervous stimulation.

What are key microscopic and functional characteristics of smooth muscle?

Smooth muscle fibers are short, spindle-shaped with a single central nucleus, lack visible striations and T-tubules, have thin filaments attached to dense bodies, and undergo slow, sustained, involuntary contractions.

Which six muscles form the extrinsic eye muscle group?

Four rectus muscles (medial rectus, lateral rectus, inferior rectus, and superior rectus) and two oblique muscles (inferior oblique and superior oblique).

Which primary muscles are involved in mastication?

The temporalis and masseter muscles, which move the mandible at the temporomandibular joint.

What is the primary function of the pharyngeal constrictor muscles during swallowing?

They initiate swallowing and force the food bolus inferiorly into the esophagus.

What are the major muscles comprising the abdominal wall?

External oblique, internal oblique, transversus abdominis, and rectus abdominis.

Which muscles act as primary flexors and extensors of the elbow joint?

Elbow flexors include the biceps brachii, brachialis, and brachioradialis; the primary elbow extensor is the triceps brachii.

What muscle is the longest in the human body, and what is its action at the coxal joint?

The sartorius muscle, which flexes and rotates the thigh at the coxal joint.

What muscles compose the quadriceps femoris group, and where do they insert?

Vastus lateralis, vastus medialis, vastus intermedius, and rectus femoris; they converge at the quadriceps tendon to the patella and patellar ligament to insert on the tibial tuberosity.

What muscles make up the hamstring group, and what is their primary action on the leg?

Biceps femoris, semitendinosus, and semimembranosus; their primary action is flexing the leg.

Which major muscles perform plantar flexion versus dorsiflexion of the foot?

Plantar flexion is performed by the gastrocnemius, soleus, and fibularis longus; dorsiflexion is performed by the tibialis anterior.

What proportion of a separated blood sample is composed of erythrocytes, buffy coat, and plasma?

Erythrocytes account for approximately $44\%$, buffy coat accounts for less than $1\%$, and plasma accounts for approximately $55\%$ of a blood sample.

What normal hematocrit range is typical for adult males and adult females?

Adult males range between $42\%$ and $56\%$, whereas adult females range from $38\%$ to $46\%$.

What is the molecular structure of a hemoglobin molecule?

Hemoglobin consists of four protein globin chains (2 alpha chains and 2 beta chains), each containing a red-pigmented heme group with an iron ($\text{Fe}^+$) ion in its center capable of binding an oxygen molecule.

How are aged erythrocytes recycled in the body?

Aged erythrocytes are phagocytized in the liver and spleen; membrane and globin proteins are broken down into amino acids, iron is transported by transferrin and stored by ferritin in the liver, and heme (minus iron) is converted to biliverdin and bilirubin, which is secreted in bile.

What surface antigens and plasma antibodies characterize ABO blood types?

Type A has surface antigen A and anti-B antibodies; Type B has surface antigen B and anti-A antibodies; Type AB has surface antigens A and B and neither antibody; Type O has neither surface antigen and both anti-A and anti-B antibodies.

What are the three types of granulocytes and their characteristics?

Neutrophils ($60\text{--}70\%$ of leukocytes; phagocytic with lobed nucleus), Eosinophils ($2\text{--}4\%$; red granules with two-lobed nucleus, phagocytic), and Basophils ($0.5\text{--}1\%$; purple granules containing histamine).

What are the major types of agranulocytes and their primary immune roles?

Lymphocytes (T-cells that manage immune response, B-cells that produce antibodies, and NK cells that attack abnormal cells) and Monocytes ($3\text{--}8\%$ of leukocytes, which become macrophages that phagocytize debris and pathogens).

What are the major plasma proteins and their relative percentages?

Albumins ($58\%$), globulins ($37\%$), fibrinogen ($4\%$), and regulatory proteins ($<1\%$).

How do pulmonary and systemic circuits differ in the heart?

The pulmonary circuit (right side of heart, pulmonary arteries/veins) conveys CO2-rich blood to the lungs for O2 replenishment, whereas the systemic circuit (left side of heart, aorta) carries oxygenated blood to all body tissues.

What internal structures prevent atrioventricular valve eversion into the atria during ventricular contraction?

Papillary muscles and chordae tendineae.

What are the three layers of the heart wall?

Epicardium (visceral layer of serous pericardium), myocardium (thickest, middle cardiac muscle layer), and endocardium (thin endothelial internal surface).

What sequence of structures transmits a muscle impulse through the heart's conduction system?

Sinoatrial (SA) node (pacemaker) $\rightarrow$ internodal conduction pathway $\rightarrow$ atrioventricular (AV) node $\rightarrow$ atrioventricular (AV) bundle (bundle of His) $\rightarrow$ right and left bundle branches $\rightarrow$ Purkinje fibers.

What are the three main tunics of a blood vessel wall?

Tunica intima (innermost endothelium), tunica media (middle smooth muscle layer for vasoconstriction and vasodilation), and tunica externa (outermost connective tissue layer).

What is the structural and functional significance of the Circle of Willis?

An arterial anastomosis around the sella turcica that equalizes blood pressure in the brain and provides collateral channels if a vessel becomes blocked.

What is the purpose of the Hepatic Portal System?

It drains venous blood from the GI tract and shunts it to the liver for processing and storage of absorbed nutrients before the blood exits through hepatic veins into the inferior vena cava.

What regions of the body are drained by the right lymphatic duct versus the thoracic duct?

The right lymphatic duct drains the upper right quadrant of the body, whereas the thoracic duct drains the left side of the head, neck, chest, left upper limb, and all body regions inferior to the diaphragm.

Where do T-lymphocytes and B-lymphocytes mature in the human body?

T-lymphocytes mature in the thymus, whereas B-lymphocytes mature in the red bone marrow.

What are the primary functions of the red pulp versus white pulp in the spleen?

White pulp initiates an immune response when antigens are found in blood; red pulp serves as a reservoir for erythrocytes and platelets and phagocytizes old, defective erythrocytes and platelets.

What structural changes occur to the thymus from infancy through adulthood?

The thymus is quite large in infants/children and grows until puberty, after which its cells regress and are replaced by adipose tissue, causing it to atrophy and become almost nonfunctional in adults.