Anatomy and Physiology 2: Test 2 Review (Chapters 21, 23, and 24)

Comprehensive vocabulary flashcards covering Metabolism and Nutrition, the Digestive System, and the Lymphatic System & Immunity from Chapters 21, 23, and 24 for Anatomy & Physiology 2 Lecture Test 2.

Catabolic reactions

Metabolic reactions that break down complex molecules into simpler ones, typically releasing energy in the form of $ATP$ and heat.

Anabolic reactions

Metabolic pathways that synthesize complex molecules from simpler precursors, requiring an input of energy ($ATP$).

Glycolysis

The initial, anaerobic phase of cellular respiration occurring in the cytoplasm that breaks down one glucose molecule into two pyruvate molecules, yielding a net of $2\text{ ATP}$ and reducing $NAD^+$ to $NADH$.

Kreb's cycle

The cyclic aerobic pathway in the mitochondrial matrix that oxidizes acetyl groups to $CO_2$, reducing electron carriers ($NAD^+$ to $NADH$ and $FAD$ to $FADH_2$) and producing $ATP$ by substrate-level phosphorylation.

Electron transport chain

A series of membrane-bound protein complexes in the inner mitochondrial membrane where $NADH$ and $FADH_2$ are oxidized, driving proton pumping and oxidative phosphorylation to produce the majority of cellular $ATP$.

Glycogenesis

The anabolic process of synthesizing glycogen from glucose monomers for storage, occurring primarily in hepatocytes and skeletal muscle fibers under the influence of insulin.

Gluconeogenesis

The synthesis of glucose from non-carbohydrate precursors (such as glycerol, lactate, and glucogenic amino acids), stimulated by glucagon and cortisol during famine or post-absorptive states.

Glucose sparing

The metabolic shift during the post-absorptive phase where most non-neural tissues switch to burning fatty acids and ketones, preserving available blood glucose for the brain.

Lipogenesis

The metabolic pathway of synthesizing triglycerides from excess fatty acids, glycerol, or acetyl-CoA derived from dietary carbohydrates and proteins, occurring in adipose tissue and the liver.

Lipolysis

The breakdown of stored triglycerides into free fatty acids and glycerol by lipase enzymes during famine or the post-absorptive state.

Beta oxidation

The catabolic sequence in mitochondria that cleaves fatty acid chains into two-carbon acetyl-CoA units to enter the Kreb's cycle, producing reduced coenzymes ($NADH$ and $FADH_2$).

Ketogenesis

The formation of ketone bodies (acetoacetate, beta-hydroxybutyrate, and acetone) in the liver from excess acetyl-CoA when carbohydrate availability is low or fatty acid oxidation is high.

Basal Metabolic Rate (BMR)

The baseline energy expenditure of an individual at rest, awake, in a post-absorptive state, and in a thermoneutral environment to maintain essential bodily functions.

Body Mass Index (BMI)

A screening metric of body composition calculated from weight relative to height, categorized into ranges: underweight ($< 18.5$), normal weight ($18.5 - 24.9$), overweight ($25 - 29.9$), and obesity ($\ge 30$).

Fat-soluble vitamins

Micronutrients absorbed with dietary lipids and stored in body tissues and liver, consisting of vitamins $A$, $D$, $E$, and $K$.

Water-soluble vitamins

Essential organic cofactors dissolved in body fluids, not significantly stored, and excreted in urine, including the $B$-complex vitamins and vitamin $C$.

Major minerals and trace elements

Inorganic dietary essentials classified by physiological requirement: major minerals (needed in larger daily amounts, such as calcium, phosphorus, potassium, sulfur, sodium, chloride, magnesium) and trace elements (needed in minute quantities, such as iron, iodine, zinc).

Insulin

A pancreatic beta-cell hormone dominant during the absorptive phase that lowers blood glucose by promoting cellular glucose uptake, glycogenesis, lipogenesis, and protein synthesis.

Glucagon

A pancreatic alpha-cell hormone dominant during the post-absorptive phase that raises blood glucose by stimulating hepatic glycogenolysis, gluconeogenesis, and lipolysis.

Layers of the alimentary canal wall

The four concentric histological tunics: mucosa (epithelium, lamina propria, muscularis mucosae), submucosa (connective tissue, blood vessels, submucosal plexus), muscularis externa (circular and longitudinal smooth muscle, myenteric plexus), and serosa or adventitia.

Phases of gastric digestion

The three regulated stages of gastric activity: the cephalic phase (triggered by sight, smell, or thought of food via the vagus nerve), gastric phase (activated by stomach distension, peptides, and rising pH), and intestinal phase (initiated by chyme entering the duodenum, triggering inhibitory enterogastric reflexes and enterogastrones).

Bile

A yellow-green fluid synthesized by hepatocytes in the liver, stored and concentrated in the gallbladder, containing bile salts that mechanically emulsify lipids for chemical digestion.

Pancreatic juice

An alkaline digestive secretion rich in bicarbonate (to neutralize acidic chyme) and enzymes including pancreatic amylase, pancreatic lipase, nucleases, and inactive proteases (trypsinogen, chymotrypsinogen, procarboxypeptidase).

Small intestine regions

The three anatomical segments of the primary site for digestion and nutrient absorption: the duodenum, jejunum, and ileum.

Large intestine

The terminal organ of the alimentary tract (comprising cecum, appendix, colon, rectum, and anal canal) characterized by teniae coli, haustra, and epiploic appendages, responsible for water/electrolyte absorption, feces formation, and housing beneficial microbiota.

Digestive enzymes

Biological catalysts that hydrolyze polymers into absorbable monomers: salivary and pancreatic amylase/brush border enzymes for carbohydrates; pepsin, trypsin, chymotrypsin, and peptidases for proteins; lipases for lipids; and nucleases for nucleic acids.

Lymph

Recovered interstitial fluid that enters closed-ended lymphatic capillaries, carrying excess fluid, leaked proteins, dietary lipids (chyle), and lymphocytes back to the venous circulation.

Lymph nodes

Encapsulated secondary lymphoid organs positioned along lymphatic vessels that filter lymph and house macrophages, dendritic cells, $B$ cells, and $T$ cells to initiate immune responses.

Thymus

A bilobed primary lymphoid organ located in the superior mediastinum where pre-$T$ cells undergo maturation, differentiation, and immunocompetence selection before atrophy after puberty.

Spleen

The largest secondary lymphoid organ, containing red pulp (phagocytosis of old erythrocytes and platelets) and white pulp (lymphoid tissue monitoring blood for circulating pathogens).

Barrier defenses

Mechanical, chemical, and physical surface structures that prevent pathogen entry, including intact skin epidermis, mucous membranes, keratin, sebum, gastric acid, and lysozyme in secretions.

Innate (nonspecific) defenses

Non-adaptive, immediate host defense mechanisms present at birth that recognize broad pathogen-associated patterns, including phagocytes (neutrophils, macrophages), natural killer ($NK$) cells, inflammation, fever, interferons, and complement.

Inflammatory response

A localized innate tissue reaction to injury or infection characterized by redness (rubor), heat (calor), swelling (tumor), and pain (dolor), mediated by histamine, prostaglandins, and leukotrienes to isolate damage and recruit leukocytes.

Antigen presenting cells (APCs)

Specialized immune cells (dendritic cells, macrophages, and $B$ cells) that engulf antigens, process them, and display antigenic peptides bound to $MHC\text{ II}$ molecules on their surfaces to activate helper $T$ cells.

T cell mediated response

Cellular adaptive immunity driven by activated $T$ lymphocytes, where cytotoxic $T$ ($CD8^+$) cells destroy infected or abnormal host cells and helper $T$ ($CD4^+$) cells secrete cytokines to coordinate immune activity.

B cells

Lymphocytes responsible for humoral immunity that mature in red bone marrow; upon antigen binding and helper $T$ stimulation, they proliferate and differentiate into plasma cells that secrete antibodies and memory $B$ cells.

Antibodies

Immunoglobulins produced by plasma cells that bind specifically to antigens, neutralizing toxins/viruses, activating complement, promoting agglutination/precipitation, and enhancing phagocytosis (opsonization).

Primary vs secondary immune responses

The primary response is the initial exposure to an antigen with a longer latent period and lower antibody titers (mainly $IgM$); the secondary (anamnestic) response is mediated by memory cells, reacting rapidly with significantly higher, long-lasting antibody titers (predominantly $IgG$).

Active immunity

Immune protection resulting from the host producing its own antibodies and memory cells following natural infection (naturally acquired) or vaccination (artificially acquired).

Passive immunity

Temporary immune protection conferred by the direct transfer of preformed antibodies from another individual, such as transplacental/breastmilk transfer (naturally acquired) or antivenom/immune globulin injection (artificially acquired), providing immediate but non-memory defense.

Allergic reactions

Exaggerated or inappropriate hypersensitivity immune responses triggered by benign environmental antigens (allergens), classified based on the immune cells involved (e.g., $IgE$-mast cell/basophil-mediated Immediate Type I vs. $T$ cell-mediated Delayed Type IV).