#!/usr/bin/env python3
"""
BNYS 1st Year Physiology Study Notes PDF Generator
MGR University | Generated: July 2026
"""

from reportlab.lib.pagesizes import A4
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.colors import HexColor, white, black
from reportlab.lib.units import cm, mm
from reportlab.platypus import (
    SimpleDocTemplate, Paragraph, Spacer, Table, TableStyle,
    HRFlowable, PageBreak, KeepTogether
)
from reportlab.lib.enums import TA_CENTER, TA_LEFT, TA_JUSTIFY
from reportlab.platypus import BaseDocTemplate, Frame, PageTemplate

OUTPUT = "/home/daytona/workspace/bnys-physiology/BNYS_Physiology_Notes.pdf"

# ── Colours ──────────────────────────────────────────────────────────────────
DARK_BLUE   = HexColor("#1A3A5C")
MID_BLUE    = HexColor("#2E6DA4")
LIGHT_BLUE  = HexColor("#D6E8F7")
ACCENT      = HexColor("#E8941A")
LIGHT_GREY  = HexColor("#F5F5F5")
DARK_GREY   = HexColor("#444444")
GREEN       = HexColor("#2E7D32")
RED         = HexColor("#C62828")
PURPLE      = HexColor("#6A1B9A")
TEAL        = HexColor("#00695C")

def make_styles():
    base = getSampleStyleSheet()

    styles = {
        "title": ParagraphStyle("title",
            fontSize=28, fontName="Helvetica-Bold",
            textColor=white, alignment=TA_CENTER,
            spaceAfter=6),
        "subtitle": ParagraphStyle("subtitle",
            fontSize=14, fontName="Helvetica",
            textColor=LIGHT_BLUE, alignment=TA_CENTER,
            spaceAfter=4),
        "cover_small": ParagraphStyle("cover_small",
            fontSize=11, fontName="Helvetica",
            textColor=LIGHT_BLUE, alignment=TA_CENTER,
            spaceAfter=2),
        "chapter_title": ParagraphStyle("chapter_title",
            fontSize=20, fontName="Helvetica-Bold",
            textColor=white, alignment=TA_LEFT,
            spaceAfter=4, spaceBefore=2),
        "section_head": ParagraphStyle("section_head",
            fontSize=14, fontName="Helvetica-Bold",
            textColor=DARK_BLUE, spaceAfter=6, spaceBefore=12,
            borderPad=4),
        "subsection_head": ParagraphStyle("subsection_head",
            fontSize=12, fontName="Helvetica-Bold",
            textColor=MID_BLUE, spaceAfter=4, spaceBefore=8),
        "body": ParagraphStyle("body",
            fontSize=10, fontName="Helvetica",
            textColor=DARK_GREY, spaceAfter=4, leading=15,
            alignment=TA_JUSTIFY),
        "bullet": ParagraphStyle("bullet",
            fontSize=10, fontName="Helvetica",
            textColor=DARK_GREY, spaceAfter=3, leading=14,
            leftIndent=16, bulletIndent=4),
        "key_box": ParagraphStyle("key_box",
            fontSize=10, fontName="Helvetica-Bold",
            textColor=DARK_BLUE, spaceAfter=2, leading=14),
        "note": ParagraphStyle("note",
            fontSize=9, fontName="Helvetica-Oblique",
            textColor=HexColor("#555555"), spaceAfter=3, leading=13,
            leftIndent=8),
        "table_header": ParagraphStyle("table_header",
            fontSize=10, fontName="Helvetica-Bold",
            textColor=white, alignment=TA_CENTER),
        "table_cell": ParagraphStyle("table_cell",
            fontSize=9, fontName="Helvetica",
            textColor=DARK_GREY, alignment=TA_LEFT, leading=13),
        "toc_entry": ParagraphStyle("toc_entry",
            fontSize=11, fontName="Helvetica",
            textColor=DARK_BLUE, spaceAfter=3, leading=16,
            leftIndent=10),
        "toc_title": ParagraphStyle("toc_title",
            fontSize=16, fontName="Helvetica-Bold",
            textColor=DARK_BLUE, spaceAfter=10, alignment=TA_CENTER),
    }
    return styles

S = make_styles()

def hr(color=MID_BLUE, thickness=1):
    return HRFlowable(width="100%", thickness=thickness, color=color, spaceAfter=6, spaceBefore=2)

def chapter_banner(title, color=DARK_BLUE):
    data = [[Paragraph(title, S["chapter_title"])]]
    t = Table(data, colWidths=[17*cm])
    t.setStyle(TableStyle([
        ("BACKGROUND", (0,0), (-1,-1), color),
        ("ROWBACKGROUNDS", (0,0), (-1,-1), [color]),
        ("LEFTPADDING",  (0,0), (-1,-1), 14),
        ("RIGHTPADDING", (0,0), (-1,-1), 14),
        ("TOPPADDING",   (0,0), (-1,-1), 10),
        ("BOTTOMPADDING",(0,0), (-1,-1), 10),
        ("ROUNDEDCORNERS", [6]),
    ]))
    return t

def key_point_box(items, title="Key Points", color=LIGHT_BLUE, title_color=DARK_BLUE):
    rows = [[Paragraph(f"<b>{title}</b>", ParagraphStyle("kh",
                fontSize=11, fontName="Helvetica-Bold",
                textColor=title_color))]]
    for item in items:
        rows.append([Paragraph(f"• {item}", S["key_box"])])
    t = Table(rows, colWidths=[16.5*cm])
    t.setStyle(TableStyle([
        ("BACKGROUND", (0,0), (0,0), color),
        ("BACKGROUND", (0,1), (-1,-1), HexColor("#EAF3FB")),
        ("LEFTPADDING",  (0,0), (-1,-1), 10),
        ("RIGHTPADDING", (0,0), (-1,-1), 10),
        ("TOPPADDING",   (0,0), (-1,-1), 5),
        ("BOTTOMPADDING",(0,0), (-1,-1), 5),
        ("BOX", (0,0), (-1,-1), 1, MID_BLUE),
        ("INNERGRID", (0,0), (-1,-1), 0.25, HexColor("#BBDEFB")),
    ]))
    return t

def simple_table(headers, rows, col_widths=None):
    if col_widths is None:
        n = len(headers)
        col_widths = [16.5*cm / n] * n
    header_row = [Paragraph(h, S["table_header"]) for h in headers]
    data = [header_row]
    for row in rows:
        data.append([Paragraph(str(c), S["table_cell"]) for c in row])
    t = Table(data, colWidths=col_widths)
    t.setStyle(TableStyle([
        ("BACKGROUND",    (0,0), (-1,0), DARK_BLUE),
        ("ROWBACKGROUNDS",(0,1), (-1,-1), [white, LIGHT_GREY]),
        ("GRID",          (0,0), (-1,-1), 0.5, HexColor("#BBBBBB")),
        ("LEFTPADDING",   (0,0), (-1,-1), 6),
        ("RIGHTPADDING",  (0,0), (-1,-1), 6),
        ("TOPPADDING",    (0,0), (-1,-1), 5),
        ("BOTTOMPADDING", (0,0), (-1,-1), 5),
        ("VALIGN",        (0,0), (-1,-1), "TOP"),
    ]))
    return t


# ══════════════════════════════════════════════════════════════════════════════
# CONTENT SECTIONS
# ══════════════════════════════════════════════════════════════════════════════

def cover_page():
    elems = []
    # Big banner
    data = [[
        Paragraph("BNYS 1st Year", S["subtitle"]),
    ],[
        Paragraph("Human Physiology", S["title"]),
    ],[
        Paragraph("Comprehensive Study Notes", S["subtitle"]),
    ]]
    t = Table(data, colWidths=[17*cm])
    t.setStyle(TableStyle([
        ("BACKGROUND", (0,0), (-1,-1), DARK_BLUE),
        ("LEFTPADDING",  (0,0), (-1,-1), 20),
        ("RIGHTPADDING", (0,0), (-1,-1), 20),
        ("TOPPADDING",   (0,0), (0,0),   30),
        ("BOTTOMPADDING",(0,-1), (-1,-1), 30),
        ("TOPPADDING",   (0,1), (-1,1),   5),
        ("BOTTOMPADDING",(0,1), (-1,1),   5),
    ]))
    elems.append(t)
    elems.append(Spacer(1, 1*cm))

    info_data = [
        ["University", "The Tamil Nadu Dr. M.G.R. Medical University"],
        ["Program",    "Bachelor of Naturopathy & Yogic Sciences (BNYS)"],
        ["Year",       "1st Year"],
        ["Subject",    "Human Physiology I & II"],
        ["Reference",  "Ganong's / Guyton & Hall / Costanzo Physiology"],
        ["Prepared",   "July 2026"],
    ]
    t2 = Table(info_data, colWidths=[4.5*cm, 12*cm])
    t2.setStyle(TableStyle([
        ("ROWBACKGROUNDS", (0,0), (-1,-1), [LIGHT_BLUE, white]),
        ("FONTNAME",  (0,0), (0,-1), "Helvetica-Bold"),
        ("FONTNAME",  (1,0), (1,-1), "Helvetica"),
        ("FONTSIZE",  (0,0), (-1,-1), 10),
        ("LEFTPADDING",  (0,0), (-1,-1), 8),
        ("TOPPADDING",   (0,0), (-1,-1), 5),
        ("BOTTOMPADDING",(0,0), (-1,-1), 5),
        ("BOX",  (0,0), (-1,-1), 1, MID_BLUE),
        ("INNERGRID", (0,0), (-1,-1), 0.3, HexColor("#BBBBBB")),
    ]))
    elems.append(t2)
    elems.append(Spacer(1, 0.8*cm))

    chapters = [
        "1. Cell Physiology", "2. Blood & Hematology",
        "3. Cardiovascular System", "4. Respiratory System",
        "5. Digestive System", "6. Nervous System",
        "7. Endocrine System", "8. Renal Physiology",
        "9. Muscle Physiology", "10. Reproductive Physiology",
    ]
    elems.append(Paragraph("Contents at a Glance", S["toc_title"]))
    for ch in chapters:
        elems.append(Paragraph(ch, S["toc_entry"]))
    elems.append(PageBreak())
    return elems


def chapter_1():
    """Cell Physiology"""
    elems = []
    elems.append(chapter_banner("Chapter 1: Cell Physiology"))
    elems.append(Spacer(1, 0.4*cm))

    elems.append(Paragraph("1.1 Cell Structure", S["section_head"]))
    elems.append(hr())
    elems.append(Paragraph(
        "The cell is the fundamental structural and functional unit of all living organisms. "
        "Human cells are <b>eukaryotic</b> - they possess a membrane-bound nucleus and specialised organelles.",
        S["body"]))

    organelles = [
        ["Organelle", "Structure", "Function"],
        ["Nucleus", "Double membrane, contains DNA", "Controls cell activities; stores genetic info"],
        ["Mitochondria", "Double membrane, cristae", "ATP production (cellular respiration)"],
        ["Endoplasmic Reticulum (RER)", "Ribosomes on surface", "Protein synthesis & modification"],
        ["Endoplasmic Reticulum (SER)", "Smooth, no ribosomes", "Lipid synthesis; detoxification"],
        ["Golgi Apparatus", "Flattened membrane sacs", "Protein packaging & secretion"],
        ["Lysosomes", "Membrane-bound vesicles", "Intracellular digestion (hydrolytic enzymes)"],
        ["Ribosomes", "rRNA + protein", "Site of protein synthesis"],
        ["Cytoskeleton", "Microfilaments, microtubules", "Cell shape, movement, organelle transport"],
    ]
    elems.append(simple_table(organelles[0], organelles[1:], [4*cm, 5.5*cm, 7*cm]))
    elems.append(Spacer(1, 0.3*cm))

    elems.append(Paragraph("1.2 Cell Membrane", S["section_head"]))
    elems.append(hr())
    elems.append(Paragraph(
        "The <b>Fluid Mosaic Model</b> (Singer & Nicolson, 1972) describes the plasma membrane as a "
        "phospholipid bilayer with embedded proteins that can move laterally.",
        S["body"]))
    elems.append(Paragraph("<b>Components:</b>", S["subsection_head"]))
    for item in [
        "Phospholipids - hydrophilic head (faces water) + hydrophobic tail (faces inward)",
        "Cholesterol - stabilises membrane fluidity; prevents crystallisation at low temperatures",
        "Integral proteins - span the bilayer; include ion channels, transporters, receptors",
        "Peripheral proteins - attached to inner/outer surface; include enzymes and structural proteins",
        "Glycoproteins & Glycolipids - cell recognition, immune function",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("1.3 Membrane Transport", S["section_head"]))
    elems.append(hr())
    transport = [
        ["Type", "Energy", "Carrier?", "Direction", "Example"],
        ["Simple Diffusion", "None", "No", "High → Low", "O₂, CO₂, lipids"],
        ["Facilitated Diffusion", "None", "Yes", "High → Low", "Glucose (GLUT), ions"],
        ["Active Transport (Primary)", "ATP", "Yes", "Low → High", "Na⁺/K⁺ ATPase"],
        ["Active Transport (Secondary)", "Gradient", "Yes", "Coupled", "Na⁺/Glucose cotransport"],
        ["Osmosis", "None", "No", "H₂O moves", "Red cell in hypotonic"],
        ["Endocytosis", "ATP", "Vesicle", "Into cell", "Phagocytosis"],
        ["Exocytosis", "ATP", "Vesicle", "Out of cell", "Neurotransmitter release"],
    ]
    elems.append(simple_table(transport[0], transport[1:], [3.5*cm, 2.5*cm, 2*cm, 3*cm, 5.5*cm]))

    elems.append(Spacer(1, 0.3*cm))
    elems.append(key_point_box([
        "Na⁺/K⁺ ATPase pumps 3 Na⁺ out and 2 K⁺ in per ATP hydrolysed - maintains RMP",
        "Osmolarity of plasma = ~285-295 mOsm/kg",
        "Isotonic = 0.9% NaCl (normal saline) or 5% dextrose",
        "Oncotic pressure (colloid osmotic) is mainly due to albumin (~25 mmHg)",
    ], "Key Points - Cell Membrane"))

    elems.append(Paragraph("1.4 Resting Membrane Potential (RMP)", S["section_head"]))
    elems.append(hr())
    elems.append(Paragraph(
        "RMP is the electrical potential difference across the plasma membrane of a cell at rest. "
        "It is <b>-70 mV</b> in neurons (inside negative relative to outside).",
        S["body"]))
    for item in [
        "Maintained by Na⁺/K⁺ ATPase and differential permeability",
        "K⁺ is the main determinant of RMP (high intracellular K⁺ leaks out)",
        "Na⁺ is high outside, low inside",
        "Cl⁻ is high outside, low inside",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("1.5 Action Potential", S["section_head"]))
    elems.append(hr())
    phases = [
        ["Phase", "Membrane Potential", "Ion Movement", "Channel State"],
        ["Resting", "-70 mV", "K⁺ leaks out slightly", "K⁺ leak channels open"],
        ["Depolarisation", "-70 → +30 mV", "Na⁺ rushes IN", "Voltage-gated Na⁺ opens"],
        ["Repolarisation", "+30 → -70 mV", "K⁺ rushes OUT", "K⁺ opens, Na⁺ closes"],
        ["Hyperpolarisation", "< -70 mV", "Excess K⁺ exits", "K⁺ slow to close"],
        ["Recovery (Refractory)", "Returns to -70 mV", "Pump restores gradient", "Na⁺/K⁺ ATPase active"],
    ]
    elems.append(simple_table(phases[0], phases[1:], [3.5*cm, 3.5*cm, 5*cm, 5*cm]))
    elems.append(Paragraph(
        "<i>Note: All-or-none law - once threshold (-55 mV) is reached, full AP fires regardless of stimulus strength.</i>",
        S["note"]))
    elems.append(PageBreak())
    return elems


def chapter_2():
    """Blood & Hematology"""
    elems = []
    elems.append(chapter_banner("Chapter 2: Blood & Hematology", TEAL))
    elems.append(Spacer(1, 0.4*cm))

    elems.append(Paragraph("2.1 Composition of Blood", S["section_head"]))
    elems.append(hr())
    elems.append(Paragraph(
        "Blood is a connective tissue consisting of <b>plasma (55%)</b> and <b>formed elements (45%)</b>. "
        "Total blood volume in adults = <b>5-6 litres</b> (70 mL/kg body weight).",
        S["body"]))

    comp = [
        ["Component", "% of Blood", "Normal Value", "Function"],
        ["Plasma", "55%", "—", "Transport medium, homeostasis"],
        ["Red Blood Cells (RBC)", "44%", "M: 5.0-5.5 million/µL; F: 4.5-5.0 million/µL", "O₂ and CO₂ transport"],
        ["White Blood Cells (WBC)", "<1%", "4,000-11,000/µL", "Immunity, defence"],
        ["Platelets", "<1%", "1,50,000-4,00,000/µL", "Haemostasis, clotting"],
    ]
    elems.append(simple_table(comp[0], comp[1:], [3.5*cm, 2.5*cm, 5.5*cm, 6*cm]))

    elems.append(Paragraph("2.2 Plasma", S["section_head"]))
    elems.append(hr())
    for item in [
        "Water: 90-92% of plasma",
        "Proteins: 7-8% - Albumin (60%), Globulins (35%), Fibrinogen (4%), others",
        "Albumin - maintains oncotic pressure, transports hormones/drugs/bilirubin",
        "Globulins - alpha/beta (transport), gamma (antibodies/immunoglobulins)",
        "Fibrinogen - clotting; converted to fibrin by thrombin",
        "Inorganic salts: Na⁺, K⁺, Ca²⁺, HCO₃⁻, Cl⁻",
        "Glucose: 70-100 mg/dL (fasting)",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("2.3 Red Blood Cells (Erythrocytes)", S["section_head"]))
    elems.append(hr())
    elems.append(Paragraph("<b>Normal Values:</b>", S["subsection_head"]))
    rbc_vals = [
        ["Parameter", "Male", "Female"],
        ["RBC count", "5.0-5.5 million/µL", "4.5-5.0 million/µL"],
        ["Haemoglobin (Hb)", "13-17 g/dL", "12-15 g/dL"],
        ["Haematocrit (PCV)", "40-50%", "36-46%"],
        ["MCV", "80-100 fL", "80-100 fL"],
        ["MCH", "27-32 pg", "27-32 pg"],
        ["MCHC", "32-36 g/dL", "32-36 g/dL"],
        ["Reticulocytes", "0.5-1.5%", "0.5-1.5%"],
    ]
    elems.append(simple_table(rbc_vals[0], rbc_vals[1:], [5*cm, 5.5*cm, 6*cm]))

    elems.append(Paragraph("<b>Life cycle of RBC:</b>", S["subsection_head"]))
    for item in [
        "Site of production: Red bone marrow (adults) - process = Erythropoiesis",
        "Stimulus: Erythropoietin (EPO) from kidney in response to hypoxia",
        "RBC has no nucleus, no mitochondria - cannot divide or do oxidative phosphorylation",
        "Lifespan: 120 days",
        "Destruction: Spleen (graveyard of RBCs), liver - by macrophages",
        "Hb breakdown → Haem → Biliverdin → Bilirubin → conjugated in liver → bile",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("2.4 Haemoglobin", S["section_head"]))
    elems.append(hr())
    elems.append(Paragraph(
        "Haemoglobin (Hb) is a protein made of <b>4 polypeptide chains</b> each carrying a <b>haem</b> group. "
        "Each haem contains one Fe²⁺ ion that binds one O₂ molecule → each Hb carries 4 O₂.",
        S["body"]))
    for item in [
        "HbA (adult): 2α + 2β chains - 97% of adult Hb",
        "HbA₂: 2α + 2δ chains - 2.5% of adult Hb",
        "HbF (fetal): 2α + 2γ chains - higher O₂ affinity than HbA",
        "O₂ carrying capacity of blood = 1.34 mL O₂ per gram of Hb",
        "Oxyhaemoglobin (HbO₂) = bright red; Deoxyhaemoglobin = dark red",
        "Carbaminohaemoglobin = CO₂ carried on Hb (23% of CO₂ transport)",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("2.5 White Blood Cells (Leukocytes)", S["section_head"]))
    elems.append(hr())
    wbc = [
        ["WBC Type", "% of WBC", "Function"],
        ["Neutrophils", "60-70%", "Phagocytosis (first responders to bacterial infection)"],
        ["Eosinophils", "2-4%", "Allergic reactions; parasite defence"],
        ["Basophils", "0-1%", "Release histamine and heparin; allergic response"],
        ["Monocytes", "2-8%", "Become macrophages; phagocytosis, antigen presentation"],
        ["Lymphocytes", "20-30%", "B cells (antibody production); T cells (cell-mediated immunity)"],
    ]
    elems.append(simple_table(wbc[0], wbc[1:], [4*cm, 3*cm, 9.5*cm]))
    elems.append(Paragraph(
        "<i>Mnemonic: Never Let Monkeys Eat Bananas = Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils (most to least common)</i>",
        S["note"]))

    elems.append(Paragraph("2.6 Blood Groups", S["section_head"]))
    elems.append(hr())
    bg = [
        ["Blood Group", "Antigen on RBC", "Antibody in Plasma", "Can Donate To", "Can Receive From"],
        ["A", "A", "Anti-B", "A, AB", "A, O"],
        ["B", "B", "Anti-A", "B, AB", "B, O"],
        ["AB", "A and B", "None", "AB only", "A, B, AB, O (Universal Recipient)"],
        ["O", "None", "Anti-A & Anti-B", "A, B, AB, O (Universal Donor)", "O only"],
    ]
    elems.append(simple_table(bg[0], bg[1:], [2.5*cm, 3*cm, 3.5*cm, 4*cm, 4.5*cm]))
    elems.append(Paragraph(
        "<b>Rh System:</b> Rh positive = has D antigen. Rh negative = no D antigen. "
        "Significance: Erythroblastosis fetalis when Rh-ve mother carries Rh+ve fetus in 2nd+ pregnancy.",
        S["body"]))

    elems.append(Paragraph("2.7 Haemostasis & Coagulation", S["section_head"]))
    elems.append(hr())
    for item in [
        "Haemostasis = stoppage of bleeding - involves 3 steps:",
        "  1. Vascular spasm - immediate vasoconstriction at injury site",
        "  2. Platelet plug formation - platelet adhesion (vWF) → activation → aggregation",
        "  3. Coagulation cascade - fibrin mesh formation",
        "Extrinsic pathway - triggered by tissue factor (TF/Factor III) - faster (seconds)",
        "Intrinsic pathway - triggered by contact with damaged vessel (Factor XII) - slower",
        "Both converge at Factor X → Prothrombin → Thrombin → Fibrinogen → Fibrin",
        "Vitamin K required for Factors II, VII, IX, X (mnemonic: 1972)",
        "Anticoagulants: Heparin (activates antithrombin III); Warfarin (inhibits Vit K)",
        "PT (Prothrombin Time): tests extrinsic pathway; normal 11-13 sec",
        "aPTT: tests intrinsic pathway; normal 25-35 sec",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(PageBreak())
    return elems


def chapter_3():
    """Cardiovascular System"""
    elems = []
    elems.append(chapter_banner("Chapter 3: Cardiovascular System", HexColor("#B71C1C")))
    elems.append(Spacer(1, 0.4*cm))

    elems.append(Paragraph("3.1 Heart - Structure & Function", S["section_head"]))
    elems.append(hr())
    elems.append(Paragraph(
        "The heart is a hollow, muscular organ located in the mediastinum. "
        "It has 4 chambers: 2 atria (receiving) and 2 ventricles (pumping). "
        "Weight: ~250-300g in adults.",
        S["body"]))
    for item in [
        "Right side: receives deoxygenated blood → pumps to lungs (pulmonary circulation)",
        "Left side: receives oxygenated blood from lungs → pumps to body (systemic circulation)",
        "Valves: Tricuspid (RA→RV), Pulmonary (RV→PA), Mitral/Bicuspid (LA→LV), Aortic (LV→Ao)",
        "Cardiac muscle = involuntary, striated, branched, connected by intercalated discs",
        "Intercalated discs contain gap junctions → electrical coupling → functional syncytium",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("3.2 Cardiac Cycle", S["section_head"]))
    elems.append(hr())
    cycle = [
        ["Phase", "Duration", "Pressure/Volume Change", "Valves"],
        ["Isovolumetric Contraction", "0.05 sec", "LV pressure rises rapidly; volume constant", "All closed"],
        ["Rapid Ejection", "0.09 sec", "Blood ejected; LV pressure peaks (~120 mmHg)", "Aortic open"],
        ["Reduced Ejection", "0.13 sec", "Continued ejection at slowing rate", "Aortic open"],
        ["Isovolumetric Relaxation", "0.08 sec", "LV pressure falls; volume constant", "All closed"],
        ["Rapid Filling", "0.11 sec", "LV fills rapidly; volume rises fast", "Mitral open"],
        ["Reduced Filling (Diastasis)", "0.19 sec", "Slow filling; low pressure gradient", "Mitral open"],
        ["Atrial Systole", "0.11 sec", "Atrial contraction adds 20% more volume", "Mitral open"],
    ]
    elems.append(simple_table(cycle[0], cycle[1:], [4*cm, 2.5*cm, 5.5*cm, 5*cm]))
    elems.append(Paragraph(
        "<i>Total cardiac cycle duration = 0.8 sec at HR 75 bpm. Systole = 0.3 sec; Diastole = 0.5 sec.</i>",
        S["note"]))

    elems.append(Paragraph("3.3 Cardiac Output (CO)", S["section_head"]))
    elems.append(hr())
    elems.append(Paragraph(
        "<b>CO = Stroke Volume (SV) × Heart Rate (HR)</b><br/>"
        "Normal CO = 70 mL × 75 bpm = 5,250 mL/min ≈ 5 L/min",
        S["body"]))
    for item in [
        "Stroke Volume = End-Diastolic Volume (EDV) - End-Systolic Volume (ESV)",
        "EDV (preload) ≈ 120-130 mL; ESV ≈ 50-60 mL; SV ≈ 70 mL",
        "Ejection Fraction (EF) = SV/EDV × 100 = normal 55-70%",
        "Frank-Starling Law: ↑ preload → ↑ stretch of myocardium → ↑ force of contraction",
        "Afterload: resistance ventricle must overcome to eject blood (= aortic pressure for LV)",
        "Contractility (Inotropy): intrinsic ability of cardiac muscle to develop force",
        "Cardiac Index = CO / Body Surface Area = 2.5-4.0 L/min/m²",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("3.4 Blood Pressure (BP)", S["section_head"]))
    elems.append(hr())
    bp_data = [
        ["Category", "Systolic (mmHg)", "Diastolic (mmHg)"],
        ["Normal", "< 120", "< 80"],
        ["Elevated", "120-129", "< 80"],
        ["Hypertension Stage 1", "130-139", "80-89"],
        ["Hypertension Stage 2", "≥ 140", "≥ 90"],
        ["Hypotension", "< 90", "< 60"],
    ]
    elems.append(simple_table(bp_data[0], bp_data[1:], [5*cm, 5*cm, 5*cm]))
    for item in [
        "Pulse Pressure = Systolic - Diastolic = 120 - 80 = 40 mmHg",
        "Mean Arterial Pressure (MAP) = Diastolic + 1/3 Pulse Pressure = 80 + 13 = 93 mmHg",
        "MAP = CO × Total Peripheral Resistance (TPR)",
        "Korotkoff sounds: Phase I (systolic BP) → Phase V (diastolic BP)",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("3.5 ECG (Electrocardiogram)", S["section_head"]))
    elems.append(hr())
    elems.append(Paragraph(
        "ECG records the electrical activity of the heart from the body surface.",
        S["body"]))
    ecg = [
        ["Wave/Interval", "Represents", "Normal Duration/Value"],
        ["P wave", "Atrial depolarisation (SA node → AV node)", "< 0.12 sec; < 0.25 mV"],
        ["PR interval", "AV conduction time", "0.12 - 0.20 sec"],
        ["QRS complex", "Ventricular depolarisation", "< 0.12 sec"],
        ["ST segment", "Plateau of ventricular AP", "Isoelectric (flat)"],
        ["T wave", "Ventricular repolarisation", "Upright in most leads"],
        ["QT interval", "Total ventricular systole", "< 0.44 sec (corrected)"],
    ]
    elems.append(simple_table(ecg[0], ecg[1:], [3.5*cm, 7*cm, 6*cm]))

    elems.append(Paragraph("3.6 Cardiac Conduction System", S["section_head"]))
    elems.append(hr())
    for item in [
        "SA Node (Sinoatrial) → pace maker of the heart → 60-100 impulses/min",
        "AV Node (Atrioventricular) → delays impulse by 0.1 sec (allows atrial filling)",
        "Bundle of His → transmits to ventricles",
        "Right & Left Bundle Branches → divide for each ventricle",
        "Purkinje Fibres → rapid distribution to ventricular myocardium",
        "Intrinsic rate: SA node 60-100; AV node 40-60; Purkinje 20-40 bpm",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))
    elems.append(PageBreak())
    return elems


def chapter_4():
    """Respiratory System"""
    elems = []
    elems.append(chapter_banner("Chapter 4: Respiratory System", HexColor("#1B5E20")))
    elems.append(Spacer(1, 0.4*cm))

    elems.append(Paragraph("4.1 Anatomy Overview", S["section_head"]))
    elems.append(hr())
    for item in [
        "Upper airways: nose, nasopharynx, oropharynx, larynx",
        "Lower airways: trachea → primary bronchi → secondary bronchi → tertiary → bronchioles → respiratory bronchioles → alveolar ducts → alveoli",
        "Alveoli: ~300-500 million; total surface area ~70-80 m²",
        "Type I pneumocytes: gas exchange (thin, flat - 95% of surface)",
        "Type II pneumocytes: produce surfactant, repair epithelium",
        "Surfactant: dipalmitoyl phosphatidylcholine (DPPC); reduces surface tension, prevents alveolar collapse",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("4.2 Lung Volumes & Capacities", S["section_head"]))
    elems.append(hr())
    lung_vol = [
        ["Parameter", "Definition", "Normal Value"],
        ["Tidal Volume (TV)", "Air moved per normal breath", "500 mL"],
        ["Inspiratory Reserve Vol (IRV)", "Extra air inspired forcibly", "3,000 mL"],
        ["Expiratory Reserve Vol (ERV)", "Extra air expired forcibly", "1,100 mL"],
        ["Residual Volume (RV)", "Air remaining after max expiration", "1,200 mL"],
        ["Inspiratory Capacity (IC)", "TV + IRV", "3,500 mL"],
        ["Functional Residual Capacity (FRC)", "ERV + RV", "2,300 mL"],
        ["Vital Capacity (VC)", "TV + IRV + ERV", "4,600 mL"],
        ["Total Lung Capacity (TLC)", "VC + RV", "5,800 mL"],
        ["FEV₁", "Forced expiration in 1st second", ">80% of FVC"],
    ]
    elems.append(simple_table(lung_vol[0], lung_vol[1:], [4.5*cm, 6*cm, 6*cm]))

    elems.append(Paragraph("4.3 Mechanics of Breathing", S["section_head"]))
    elems.append(hr())
    for item in [
        "Inspiration = active process; diaphragm contracts (descends 1.5 cm)",
        "External intercostals contract → ribs elevate → thoracic volume ↑",
        "Intrathoracic pressure falls below atmospheric → air flows IN",
        "Expiration = passive at rest (elastic recoil of lungs)",
        "Forced expiration uses internal intercostals, abdominal muscles",
        "Compliance = change in volume per unit change in pressure (normal ~200 mL/cmH₂O)",
        "Airway resistance: mainly in medium bronchi; increases in asthma (bronchoconstriction)",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("4.4 Gas Exchange & Transport", S["section_head"]))
    elems.append(hr())
    gas_transport = [
        ["Gas", "Transport in Blood", "% of Total"],
        ["O₂ dissolved in plasma", "Henry's law", "1.5%"],
        ["O₂ bound to haemoglobin", "HbO₂", "98.5%"],
        ["CO₂ as bicarbonate (HCO₃⁻)", "Chloride shift (Band 3 protein)", "70%"],
        ["CO₂ as carbaminohaemoglobin", "Bound to Hb (globin chains)", "23%"],
        ["CO₂ dissolved in plasma", "Henry's law", "7%"],
    ]
    elems.append(simple_table(gas_transport[0], gas_transport[1:], [5*cm, 6.5*cm, 5*cm]))
    elems.append(Paragraph(
        "<b>Chloride Shift (Hamburger Shift):</b> CO₂ → H₂CO₃ (carbonic anhydrase) → H⁺ + HCO₃⁻. "
        "HCO₃⁻ exits RBC → Cl⁻ enters to maintain electrical neutrality.",
        S["body"]))

    elems.append(Paragraph("4.5 Regulation of Respiration", S["section_head"]))
    elems.append(hr())
    for item in [
        "Respiratory centres in brainstem: Dorsal (DRG) and Ventral (VRG) respiratory groups in medulla",
        "Pneumotaxic centre (upper pons): limits inspiration, controls rate",
        "Apneustic centre (lower pons): prolongs inspiration",
        "Central chemoreceptors (medulla): respond to H⁺ (from CO₂); most powerful stimulus to breathe",
        "Peripheral chemoreceptors (carotid & aortic bodies): respond to ↓PaO₂, ↑PaCO₂, ↓pH",
        "Normal PaO₂ = 95-100 mmHg; PaCO₂ = 35-45 mmHg",
        "Hering-Breuer reflex: stretch receptors in lungs → inhibit further inspiration (prevent over-inflation)",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))
    elems.append(PageBreak())
    return elems


def chapter_5():
    """Digestive System"""
    elems = []
    elems.append(chapter_banner("Chapter 5: Digestive System", HexColor("#4A148C")))
    elems.append(Spacer(1, 0.4*cm))

    elems.append(Paragraph("5.1 Overview of GI Tract", S["section_head"]))
    elems.append(hr())
    for item in [
        "Mouth → Oesophagus → Stomach → Small intestine (duodenum, jejunum, ileum) → Large intestine → Rectum → Anus",
        "Accessory organs: Salivary glands, Pancreas, Liver, Gallbladder",
        "4 layers of GI wall: Mucosa, Submucosa, Muscularis externa, Serosa",
        "Enteric Nervous System (ENS): Meissner's plexus (submucosa) & Auerbach's plexus (myenteric) - the 'gut brain'",
        "Motility: Peristalsis (propulsion) and Segmentation (mixing)",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("5.2 Gastric Secretion", S["section_head"]))
    elems.append(hr())
    gastric = [
        ["Cell Type", "Location", "Secretion", "Function"],
        ["Chief cells", "Fundus/body", "Pepsinogen", "Converted to pepsin by HCl; digests protein"],
        ["Parietal cells", "Fundus/body", "HCl & Intrinsic factor", "Kills bacteria; activates pepsin; IF for B12 absorption"],
        ["G cells", "Antrum/pylorus", "Gastrin", "Stimulates parietal cells to secrete HCl"],
        ["Mucous neck cells", "Throughout", "Mucus", "Protects stomach wall"],
        ["Enterochromaffin-like (ECL) cells", "Fundus", "Histamine", "Stimulates acid secretion"],
    ]
    elems.append(simple_table(gastric[0], gastric[1:], [4*cm, 3*cm, 3.5*cm, 6.5*cm]))

    elems.append(Paragraph("5.3 Intestinal Digestion & Absorption", S["section_head"]))
    elems.append(hr())
    absorb = [
        ["Nutrient", "Site of Absorption", "Mechanism"],
        ["Glucose/Fructose", "Duodenum/Jejunum", "Na⁺-glucose cotransport (SGLT1); GLUT5 for fructose"],
        ["Amino acids", "Jejunum", "Na⁺-dependent cotransport"],
        ["Fatty acids/Glycerol", "Jejunum", "Diffusion; form chylomicrons → lymphatics"],
        ["Fat-soluble vit (A,D,E,K)", "Jejunum/Ileum", "Bile-dependent absorption"],
        ["Vitamin B12", "Terminal Ileum", "Requires Intrinsic Factor (IF)"],
        ["Iron (Fe²⁺)", "Duodenum", "DMT1 transporter; enhanced by Vit C"],
        ["Calcium", "Duodenum", "Active transport; enhanced by Vit D & PTH"],
        ["Water", "Small & Large intestine", "Osmosis - follows solute absorption"],
    ]
    elems.append(simple_table(absorb[0], absorb[1:], [4*cm, 4*cm, 8.5*cm]))

    elems.append(Paragraph("5.4 Liver Functions", S["section_head"]))
    elems.append(hr())
    for item in [
        "Metabolism: carbohydrate (glycogenesis, glycogenolysis, gluconeogenesis), protein (transamination, deamination, urea cycle), fat (fatty acid oxidation, ketogenesis, lipoprotein synthesis)",
        "Bile production: 600-1000 mL/day; bile salts emulsify fats",
        "Detoxification: cytochrome P450 enzymes; first-pass metabolism of drugs",
        "Synthesis: albumin, clotting factors (fibrinogen, prothrombin), complement proteins",
        "Storage: glycogen (glucose), Vit A, D, B12, iron (as ferritin)",
        "Bilirubin metabolism: unconjugated (indirect) → conjugated (direct) → bile → gut → urobilinogen",
        "Kupffer cells: resident macrophages in liver sinusoids",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))
    elems.append(PageBreak())
    return elems


def chapter_6():
    """Nervous System"""
    elems = []
    elems.append(chapter_banner("Chapter 6: Nervous System", HexColor("#1A237E")))
    elems.append(Spacer(1, 0.4*cm))

    elems.append(Paragraph("6.1 Organisation", S["section_head"]))
    elems.append(hr())
    for item in [
        "Central Nervous System (CNS): Brain + Spinal cord",
        "Peripheral Nervous System (PNS): Somatic (voluntary) + Autonomic (involuntary)",
        "Autonomic NS: Sympathetic ('fight or flight') vs Parasympathetic ('rest and digest')",
        "Neurons: Sensory (afferent) → CNS → Motor (efferent) → effector",
        "Neuroglia: Astrocytes, Oligodendrocytes, Microglia, Ependymal cells (CNS); Schwann cells, Satellite cells (PNS)",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("6.2 Synaptic Transmission", S["section_head"]))
    elems.append(hr())
    for item in [
        "AP arrives at presynaptic terminal → Ca²⁺ enters through voltage-gated channels",
        "Ca²⁺ triggers exocytosis of neurotransmitter-containing vesicles",
        "Neurotransmitter diffuses across synaptic cleft (20-40 nm)",
        "Binds postsynaptic receptors → opens ion channels → EPSP or IPSP",
        "EPSP (excitatory): depolarisation (Na⁺ in) → may trigger AP if threshold reached",
        "IPSP (inhibitory): hyperpolarisation (K⁺ out or Cl⁻ in) → reduces firing",
        "Spatial & temporal summation determine whether AP fires",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("6.3 Key Neurotransmitters", S["section_head"]))
    elems.append(hr())
    nt = [
        ["Neurotransmitter", "Type", "Location/Function"],
        ["Acetylcholine (ACh)", "Excitatory/Inhibitory", "NMJ, autonomic ganglia, parasympathetic effectors; CNS memory"],
        ["Dopamine", "Mostly inhibitory", "Substantia nigra (movement); reward pathway; decreased in Parkinson's"],
        ["Serotonin (5-HT)", "Mostly inhibitory", "Mood, sleep, appetite; decreased in depression"],
        ["Noradrenaline (NE)", "Excitatory", "Sympathetic NS; arousal, attention"],
        ["GABA", "Inhibitory", "Main inhibitory NT in brain; target of benzodiazepines"],
        ["Glutamate", "Excitatory", "Main excitatory NT in CNS; learning (NMDA receptors)"],
        ["Endorphins/Enkephalins", "Inhibitory", "Pain modulation; natural opioids"],
    ]
    elems.append(simple_table(nt[0], nt[1:], [4*cm, 3*cm, 9.5*cm]))

    elems.append(Paragraph("6.4 Autonomic Nervous System (ANS)", S["section_head"]))
    elems.append(hr())
    ans = [
        ["Feature", "Sympathetic", "Parasympathetic"],
        ["Origin", "Thoraco-lumbar (T1-L2)", "Cranio-sacral (CN III,VII,IX,X; S2-4)"],
        ["Preganglionic NT", "Acetylcholine", "Acetylcholine"],
        ["Postganglionic NT", "Noradrenaline (NE)", "Acetylcholine"],
        ["Heart rate", "Increases (↑HR)", "Decreases (↓HR)"],
        ["Pupils", "Dilates (mydriasis)", "Constricts (miosis)"],
        ["Bronchi", "Dilates", "Constricts"],
        ["GI motility", "Decreases", "Increases"],
        ["Bladder", "Relaxes (urinary retention)", "Contracts (micturition)"],
        ["Sweating", "Increases (cholinergic)", "No effect"],
        ["Adrenal medulla", "Releases adrenaline/NE", "No innervation"],
    ]
    elems.append(simple_table(ans[0], ans[1:], [4.5*cm, 6*cm, 6*cm]))
    elems.append(PageBreak())
    return elems


def chapter_7():
    """Endocrine System"""
    elems = []
    elems.append(chapter_banner("Chapter 7: Endocrine System", HexColor("#E65100")))
    elems.append(Spacer(1, 0.4*cm))

    elems.append(Paragraph("7.1 Key Hormones Overview", S["section_head"]))
    elems.append(hr())
    hormones = [
        ["Gland", "Hormone", "Target", "Action"],
        ["Anterior Pituitary", "GH (Growth Hormone)", "Liver, all cells", "Growth; protein anabolism; ↑ IGF-1"],
        ["Anterior Pituitary", "TSH", "Thyroid", "Stimulates T3/T4 synthesis"],
        ["Anterior Pituitary", "ACTH", "Adrenal cortex", "Stimulates cortisol, androgens"],
        ["Anterior Pituitary", "FSH/LH", "Gonads", "Gametogenesis & sex hormone production"],
        ["Posterior Pituitary", "ADH (Vasopressin)", "Kidney collecting duct", "Water reabsorption (↑ aquaporin 2)"],
        ["Posterior Pituitary", "Oxytocin", "Uterus, breast", "Labour contractions; milk ejection"],
        ["Thyroid", "T3/T4 (thyroxine)", "All cells", "↑ BMR, protein synthesis, growth, CNS maturation"],
        ["Thyroid", "Calcitonin", "Bone, kidney", "↓ blood calcium"],
        ["Parathyroid", "PTH", "Bone, kidney, GI", "↑ blood calcium (osteoclasts, Ca reabsorption, Vit D activation)"],
        ["Adrenal cortex", "Cortisol", "Widespread", "Stress hormone; ↑ glucose; anti-inflammatory"],
        ["Adrenal cortex", "Aldosterone", "Kidney DCT", "Na⁺ retention, K⁺ excretion → ↑ BP"],
        ["Adrenal medulla", "Adrenaline (Epinephrine)", "Widespread", "Fight/flight; ↑HR, ↑BP, ↑glucose"],
        ["Pancreas - β cells", "Insulin", "Liver, muscle, fat", "↓ blood glucose; anabolic"],
        ["Pancreas - α cells", "Glucagon", "Liver", "↑ blood glucose; catabolic"],
    ]
    elems.append(simple_table(hormones[0], hormones[1:], [4*cm, 4*cm, 3.5*cm, 5*cm]))

    elems.append(Paragraph("7.2 Glucose Regulation", S["section_head"]))
    elems.append(hr())
    elems.append(Paragraph(
        "Blood glucose is maintained between <b>70-100 mg/dL</b> (fasting) through a tight hormonal balance.",
        S["body"]))
    for item in [
        "After a meal: ↑ blood glucose → β cells release insulin → glucose enters cells → glycogenesis → glucose ↓ to normal",
        "Fasting/exercise: ↓ blood glucose → α cells release glucagon → glycogenolysis + gluconeogenesis in liver → glucose ↑",
        "Counter-regulatory hormones (against insulin): glucagon, adrenaline, cortisol, GH",
        "Type 1 DM: absolute insulin deficiency (autoimmune destruction of β cells)",
        "Type 2 DM: insulin resistance + relative insulin deficiency",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))
    elems.append(PageBreak())
    return elems


def chapter_8():
    """Renal Physiology"""
    elems = []
    elems.append(chapter_banner("Chapter 8: Renal Physiology", HexColor("#006064")))
    elems.append(Spacer(1, 0.4*cm))

    elems.append(Paragraph("8.1 Kidney Structure & Function", S["section_head"]))
    elems.append(hr())
    for item in [
        "2 kidneys, each ~150g; located retroperitoneally at T12-L3",
        "Functional unit = Nephron (~1 million per kidney)",
        "Nephron parts: Glomerulus → Bowman's capsule → PCT → Loop of Henle → DCT → Collecting duct",
        "Functions: Filtration, Reabsorption, Secretion, Excretion",
        "Also: regulate blood pressure, acid-base balance, erythropoietin production, Vit D activation",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("8.2 GFR & Renal Clearance", S["section_head"]))
    elems.append(hr())
    elems.append(Paragraph(
        "GFR = Glomerular Filtration Rate = volume filtered by all glomeruli per minute. "
        "Normal GFR = <b>125 mL/min</b> (180 L/day filtered; ~1.5 L/day urine produced).",
        S["body"]))
    for item in [
        "GFR measured by inulin clearance (gold standard) or estimated by creatinine clearance",
        "Filtration fraction = GFR / Renal Plasma Flow = 125/625 = ~20%",
        "Starling forces across glomerular membrane determine GFR",
        "Autoregulation: myogenic mechanism + tubuloglomerular feedback maintain GFR despite BP changes",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("8.3 Tubular Reabsorption Summary", S["section_head"]))
    elems.append(hr())
    tubular = [
        ["Segment", "What is Reabsorbed", "Key Mechanism"],
        ["PCT", "65% of Na⁺, Cl⁻, K⁺, HCO₃⁻, glucose, amino acids, water", "Na⁺/K⁺ ATPase; cotransporters"],
        ["Loop of Henle (descending)", "Water (25%)", "Impermeable to solutes"],
        ["Loop of Henle (ascending)", "Na⁺, Cl⁻, K⁺ (25%) - NO water", "NKCC2 cotransporter (target of furosemide)"],
        ["DCT", "Na⁺, Cl⁻ (5%)", "NCC cotransporter (target of thiazides)"],
        ["Collecting Duct", "Na⁺ (3%); H₂O (ADH-dependent)", "ENaC (aldosterone); Aquaporin 2 (ADH)"],
    ]
    elems.append(simple_table(tubular[0], tubular[1:], [4*cm, 7*cm, 5.5*cm]))
    elems.append(PageBreak())
    return elems


def chapter_9():
    """Muscle Physiology"""
    elems = []
    elems.append(chapter_banner("Chapter 9: Muscle Physiology", HexColor("#37474F")))
    elems.append(Spacer(1, 0.4*cm))

    elems.append(Paragraph("9.1 Types of Muscle", S["section_head"]))
    elems.append(hr())
    muscle_types = [
        ["Property", "Skeletal", "Cardiac", "Smooth"],
        ["Shape", "Long, cylindrical", "Branched", "Spindle-shaped"],
        ["Nuclei", "Multinucleate (periphery)", "1-2 (central)", "Single (central)"],
        ["Striations", "Yes", "Yes", "No"],
        ["Control", "Voluntary", "Involuntary (autorhythmic)", "Involuntary"],
        ["Speed", "Fast", "Moderate", "Slow"],
        ["Fatigue", "Yes (fast twitch)", "No (sustained)", "Slow fatigue"],
    ]
    elems.append(simple_table(muscle_types[0], muscle_types[1:], [3.5*cm, 4.5*cm, 4.5*cm, 4*cm]))

    elems.append(Paragraph("9.2 Sliding Filament Theory", S["section_head"]))
    elems.append(hr())
    elems.append(Paragraph(
        "Muscle contraction occurs by <b>thick filaments (myosin)</b> pulling <b>thin filaments (actin)</b> toward the "
        "centre of the sarcomere - the filaments themselves do not shorten.",
        S["body"]))
    for item in [
        "Sarcomere: functional unit of striated muscle - Z line to Z line",
        "At rest: tropomyosin blocks actin-myosin binding sites",
        "AP arrives → T-tubule → SR releases Ca²⁺",
        "Ca²⁺ binds troponin C → tropomyosin moves → actin binding sites exposed",
        "Myosin head binds actin → power stroke (ADP+Pi released) → filaments slide",
        "ATP binds myosin → head detaches → ATP hydrolysis re-cocks the head",
        "Relaxation: Ca²⁺ pumped back into SR (by SERCA) → troponin-tropomyosin covers actin again",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(key_point_box([
        "Cross-bridge cycle: Attach → Power stroke → Detach → Re-cock",
        "Rigor mortis: ATP depleted after death → myosin heads permanently attached to actin",
        "Motor unit: one motor neuron + all muscle fibres it innervates",
        "Neuromuscular junction (NMJ): ACh released → binds nicotinic receptors → EPP → AP → contraction",
    ], "Key Points - Muscle Contraction"))
    elems.append(PageBreak())
    return elems


def chapter_10():
    """Reproductive Physiology"""
    elems = []
    elems.append(chapter_banner("Chapter 10: Reproductive Physiology", HexColor("#880E4F")))
    elems.append(Spacer(1, 0.4*cm))

    elems.append(Paragraph("10.1 Male Reproductive Physiology", S["section_head"]))
    elems.append(hr())
    for item in [
        "Testes: primary gonad; produce testosterone (Leydig cells) and spermatozoa (seminiferous tubules)",
        "Spermatogenesis: begins at puberty; takes ~74 days; regulated by FSH (Sertoli cells) and LH (Leydig cells)",
        "Testosterone: promotes spermatogenesis, secondary sex characteristics, anabolic effects",
        "Sertoli cells: provide nourishment to developing spermatids; form blood-testis barrier; secrete inhibin (inhibits FSH)",
        "Sperm: Head (acrosome - contains enzymes for penetrating ovum), Midpiece (mitochondria for energy), Tail (flagellum for motility)",
        "Normal sperm count: ≥ 15 million/mL; motility ≥ 40%; morphology ≥ 4%",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    elems.append(Paragraph("10.2 Female Reproductive Physiology", S["section_head"]))
    elems.append(hr())
    for item in [
        "Ovaries: produce oocytes and hormones (oestrogen, progesterone)",
        "Menstrual cycle: average 28 days",
        "Phase 1 (Days 1-5): Menstruation - shedding of endometrium",
        "Phase 2 (Days 1-13): Follicular/Proliferative - FSH stimulates follicle growth → ↑ oestrogen",
        "Ovulation (Day 14): LH surge → release of secondary oocyte",
        "Phase 3 (Days 15-28): Luteal/Secretory - corpus luteum → progesterone + oestrogen",
        "If no fertilisation: corpus luteum degenerates → hormones fall → menstruation",
        "Oestrogen: proliferates endometrium, develops female secondary sex characteristics",
        "Progesterone: prepares endometrium for implantation, maintains pregnancy",
    ]:
        elems.append(Paragraph(f"• {item}", S["bullet"]))

    menstrual = [
        ["Day", "Phase", "Dominant Hormone", "Endometrium", "FSH/LH"],
        ["1-5", "Menstruation", "None (low)", "Shed", "FSH rising"],
        ["6-13", "Proliferative", "Oestrogen", "Thickens (proliferates)", "FSH high → LH surge"],
        ["14", "Ovulation", "LH surge", "Maximal thickness", "LH peak"],
        ["15-28", "Secretory", "Progesterone", "Secretory glands develop", "Both low"],
    ]
    elems.append(simple_table(menstrual[0], menstrual[1:], [2*cm, 3*cm, 4*cm, 5*cm, 4.5*cm]))
    elems.append(PageBreak())
    return elems


def quick_reference():
    """Quick reference page with normal values"""
    elems = []
    elems.append(chapter_banner("Quick Reference: Normal Physiological Values", DARK_GREY))
    elems.append(Spacer(1, 0.3*cm))

    values = [
        ["Parameter", "Normal Range", "Unit"],
        ["Heart Rate", "60 - 100", "bpm"],
        ["Blood Pressure (Systolic/Diastolic)", "120 / 80", "mmHg"],
        ["Respiratory Rate", "12 - 20", "breaths/min"],
        ["Temperature (oral)", "36.5 - 37.5", "°C"],
        ["SpO₂", "95 - 100", "%"],
        ["Haemoglobin (Male/Female)", "13-17 / 12-15", "g/dL"],
        ["WBC count", "4,000 - 11,000", "/µL"],
        ["Platelet count", "1,50,000 - 4,00,000", "/µL"],
        ["Fasting blood glucose", "70 - 100", "mg/dL"],
        ["Serum Na⁺", "136 - 145", "mEq/L"],
        ["Serum K⁺", "3.5 - 5.0", "mEq/L"],
        ["Serum Ca²⁺ (total)", "8.5 - 10.5", "mg/dL"],
        ["Serum Cl⁻", "98 - 107", "mEq/L"],
        ["pH (arterial blood)", "7.35 - 7.45", "—"],
        ["PaO₂", "80 - 100", "mmHg"],
        ["PaCO₂", "35 - 45", "mmHg"],
        ["Serum creatinine", "0.6 - 1.2", "mg/dL"],
        ["BUN (Blood Urea Nitrogen)", "7 - 20", "mg/dL"],
        ["GFR", "> 90 (CKD < 60)", "mL/min/1.73m²"],
        ["Total serum protein", "6.0 - 8.3", "g/dL"],
        ["Albumin", "3.5 - 5.0", "g/dL"],
        ["Total bilirubin", "0.2 - 1.2", "mg/dL"],
        ["Tidal Volume", "500", "mL"],
        ["Vital Capacity (approx)", "4,600", "mL"],
        ["Cardiac Output", "4 - 8", "L/min"],
        ["Stroke Volume", "60 - 100", "mL"],
        ["Ejection Fraction", "55 - 70", "%"],
    ]
    elems.append(simple_table(values[0], values[1:], [8*cm, 5.5*cm, 3*cm]))
    return elems


# ══════════════════════════════════════════════════════════════════════════════
# BUILD PDF
# ══════════════════════════════════════════════════════════════════════════════

def build_pdf():
    doc = SimpleDocTemplate(
        OUTPUT,
        pagesize=A4,
        leftMargin=2*cm, rightMargin=2*cm,
        topMargin=2.2*cm, bottomMargin=2*cm,
        title="BNYS 1st Year Physiology Study Notes",
        author="Orris AI | MGR University",
        subject="Human Physiology",
    )

    story = []
    story += cover_page()
    story += chapter_1()
    story += chapter_2()
    story += chapter_3()
    story += chapter_4()
    story += chapter_5()
    story += chapter_6()
    story += chapter_7()
    story += chapter_8()
    story += chapter_9()
    story += chapter_10()
    story += quick_reference()

    doc.build(story)
    print(f"PDF generated: {OUTPUT}")

if __name__ == "__main__":
    build_pdf()