Anatomy and Physiology: Homeostasis, Anatomical Terminology, and Tissues

Flashcards covering introductory anatomy and physiology concepts including homeostasis, feedback loops, directional terminology, body cavities, and the four primary tissue classes.

What is the biological definition of homeostasis?

The ability to detect change, activate mechanisms that oppose it, and thereby maintain relatively stable internal conditions.

How does negative feedback maintain dynamic equilibrium in the body?

The body senses an internal change and activates mechanisms that negate or reverse it, keeping physiological conditions within a limited range around a set point.

What heat-losing and heat-gaining mechanisms are activated to regulate core body temperature around the $37.0^\circ\text{C}$ set point?

When the body is too warm, skin blood vessels dilate (vasodilation) and sweating begins; when too cold, skin blood vessels constrict (vasoconstriction) and shivering begins.

What are the three core functional components of a negative feedback loop?

1. Receptor: senses change in the body.
2. Integrating (control) center: processes sensory information, makes decisions, and directs response.
3. Effector: cell or organ that carries out the corrective action.

How does positive feedback differ functionally from negative feedback, and what is a physiological example?

Positive feedback is a self-amplifying cycle where a physiological change produces more change in the same direction; an example is the release of oxytocin and increasing uterine contractions during childbirth.

What is the correct hierarchy of human anatomical complexity from the simplest chemical level to the complete individual?

Atom $\rightarrow$ Molecule $\rightarrow$ Macromolecule $\rightarrow$ Organelle $\rightarrow$ Cell $\rightarrow$ Tissue $\rightarrow$ Organ $\rightarrow$ Organ system $\rightarrow$ Organism.

What anatomical structures are distinguished by the spelling difference between 'ileum' and 'ilium'?

The ileum is the final portion of the small intestine, whereas the ilium is a bone of the hip/pelvis.

What does standard anatomical position entail?

A stance where a person stands upright with both feet flat on the ground, arms resting at the sides, and palms facing forward.

What are the three primary anatomical planes of the human body and how do they divide it?

1. Sagittal plane: passes vertically through the body, dividing it into right and left portions (median or midsagittal divides into equal halves).
2. Frontal (coronal) plane: passes vertically, dividing the body into anterior (front) and posterior (back) portions.
3. Transverse (horizontal) plane: runs perpendicular to the long axis, dividing the body into superior (upper) and inferior (lower) portions.

In directional anatomy, what is the meaning of the terms 'ventral' and 'dorsal'?

Ventral means toward the front or belly; dorsal means toward the back or spine.

In directional anatomy, what do 'rostral' and 'caudal' mean?

Rostral means toward the forehead or nose; caudal means toward the tail or inferior end.

What do the directional terms 'proximal' and 'distal' describe?

Proximal means closer to the point of attachment or origin; distal means farther from the point of attachment or origin.

What is the difference between ipsilateral and contralateral structures?

Ipsilateral structures are on the same side of the body, whereas contralateral structures are on opposite sides of the body.

What regions comprise the axial region versus the appendicular region of the human body?

The axial region comprises the head (cephalic, facial), neck (cervical), and trunk (thoracic and abdominal regions); the appendicular region comprises the upper and lower limbs.

What serous membranes enclose the lungs and the heart in the thoracic cavity?

The pleurae (visceral pleura covering lung surface and parietal pleura lining rib cage) enclose the lungs; the pericardium (visceral pericardium on heart surface and parietal pericardium externally) encloses the heart.

What are the two layers of the peritoneum in the abdominopelvic cavity?

The parietal peritoneum lines the cavity wall, while the visceral peritoneum covers and suspends viscera from the body wall.

What is the primary role of a fixative, such as formalin, in tissue preparation for histology?

It prevents tissue decay and holds the sample together prior to sectioning and staining.

What are the four primary tissue classes in the human body?

Epithelial, connective, nervous, and muscular tissue.

What are the key histological characteristics of epithelial tissue?

Sheets of closely adhering cells one or more layers thick, avascular (nourished by underlying connective tissue), with an apical surface facing the exterior or lumen and a basal surface anchored to a basement membrane.

What distinguishes simple epithelium from stratified epithelium?

In simple epithelium, every cell touches the basement membrane; in stratified epithelium, some cells rest on top of other cells and do not contact the basement membrane.

Why is pseudostratified columnar epithelium classified as a simple epithelium?

Although nuclei appear at multiple layers giving the appearance of stratification, every cell reaches and contacts the basement membrane.

What distinguishes keratinized stratified squamous epithelium from nonkeratinized stratified squamous epithelium?

Keratinized epithelium has surface layers of dead cells packed with keratin and water-repellent glycolipids to resist abrasion (e.g., epidermis of palms/soles); nonkeratinized epithelium retains living surface cells with nuclei and covers moist areas (e.g., esophagus, oral mucosa, vagina).

What are the two major cell classes found in nervous tissue and their respective functions?

1. Neurons: nerve cells specialized to detect stimuli, respond quickly, and transmit coded electrical signals via a neurosoma, dendrites, and an axon.
2. Neuroglia (glial cells): cells that protect and assist the neurons.

What are the distinguishing features of skeletal, cardiac, and smooth muscle tissues?

Skeletal muscle is voluntary, striated, and multinucleated; cardiac muscle is involuntary, striated, contains branched myocytes with a single nucleus joined by intercalated discs; smooth muscle is involuntary, non-striated, and contains fusiform cells with a single nucleus.

What is the defining structural characteristic of connective tissue compared to epithelial tissue?

Connective tissue cells occupy less space than the extracellular matrix they secrete, and most cells are not in direct contact with each other.

What are the differences between white fat and brown fat in adipose tissue?

White fat provides thermal insulation, cushions organs, and acts as the body's primary energy reservoir; brown fat is found mainly in infants and children and functions as heat-generating tissue due to its high density of mitochondria and blood vessels.

How do chondroblasts differentiate into chondrocytes in cartilage, and why does cartilage heal slowly?

Chondroblasts secrete cartilage matrix until they become trapped within cavities called lacunae, at which point they become chondrocytes; cartilage heals slowly because it is avascular and relies on diffusion for nutrient transport.

What proportions of the skeleton are composed of compact bone versus spongy bone, and how are their matrices organized?

Compact bone makes up $85\%$ of the skeleton and is organized into cylindrical osteons with concentric lamellae; spongy (cancellous) bone makes up $15\%$ and consists of delicate struts called trabeculae filled with red bone marrow.

What proportion of total blood volume is comprised of plasma, and what are its main components?

Plasma accounts for approximately $50\%\text{--}60\%$ of normal blood volume and consists of $95\%$ water, dissolved proteins, clotting factors, electrolytes, hormones, and carbon dioxide.