Year 11 ATAR Human Biology Comprehensive Review

Comprehensive practice flashcards covering human anatomy, histology, organ physiology, reproduction, embryology, genetics, epigenetics, and oncology based on the lecture series.

Approximately how many cells make up an adult human body, and roughly how many distinct cell types exist?

An adult human body consists of approximately $75\text{ trillion}$ cells (with some estimates up to $100\text{ trillion}$) comprising approximately $200$ distinct cell types.

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

Epithelial tissue, connective tissue, muscular tissue, and nervous tissue.

What structural feature characterizes epithelial tissue?

Epithelial tissue consists of very tightly packed cells that form a continuous covering or lining over internal and external body surfaces, categorized by shape as squamous (flat), cuboidal, or columnar, and arranged as simple or stratified layers.

What are the roles of goblet cells and cilia in ciliated epithelial tissue?

Goblet cells secrete mucus to trap foreign particles and microbes, while cilia beat rhythmically to sweep the particle-laden mucus upwards away from passages such as the respiratory tract.

How does connective tissue differ structurally from epithelial tissue?

Connective tissue consists of cells that are not closely packed together but are instead separated and held within an extracellular non-cellular matrix containing fibers such as collagen and elastin.

What are the microscopic structural units of compact bone called, and what are their components?

They are called osteons (or Haversian systems), each consisting of concentric layers of bone matrix called lamellae surrounding a central Haversian canal that houses blood and lymph vessels, with mature osteocytes situated in spaces called lacunae connected by canaliculi.

What type of bone tissue is illustrated in this diagram showing open spaces, trabeculae, and bone marrow?

Spongy (cancellous) bone, which forms a porous latticework of bony plates called trabeculae with spaces containing bone marrow and blood vessels.

What are the three types of muscle tissue, and what structural feature allows rapid electrical transmission across cardiac muscle cells?

Skeletal muscle (striated, voluntary, multinucleated), smooth muscle (spindle-shaped, non-striated, involuntary, uninucleated), and cardiac muscle (striated, branching, involuntary); intercalated discs connect adjacent cardiac cells to enable coordinated contraction.

What are the three main regions of a human spermatozoon and their specific roles?

The head contains the nucleus and an enzyme-filled acrosome (which digests the outer layers of the ovum); the midpiece contains numerous mitochondria to produce $ATP$ for movement; and the tail consists of a long flagellum for propulsion.

What specific substances are contributed to semen by the seminal vesicles, prostate gland, and bulbourethral glands?

Seminal vesicles secrete fluid rich in fructose (to nourish sperm), vitamin C, prostaglandins, and clotting/liquefying enzymes; the prostate secretes citric acid, clotting/liquefying enzymes, and alkaline buffers to neutralize vaginal acidity; and the bulbourethral (Cowper's) glands secrete lubricating mucus and neutralising buffers.

How do spermatogenesis and oogenesis differ in terms of the number of functional gametes produced and meiotic continuity?

Spermatogenesis produces four viable haploid sperm continuously from puberty onwards, taking $72\text{ days}$ per cycle; oogenesis begins before birth (arresting in prophase I), resumes at puberty with unequal cytoplasmic division yielding only one viable mature ovum and $2\text{ to }3$ disintegrating polar bodies per cycle, and terminates at menopause.

Which anatomical structures of the human digestive system correspond to labels 3, 4, 9, and 10 in the diagram?

Label 3 is the liver, label 4 is the gall bladder, label 9 is the pancreas, and label 10 is the stomach.

What enzymes are found in saliva, gastric juice, and pancreatic juice, and what substrates do they act upon?

Saliva contains salivary amylase (breaks starch into disaccharides); gastric juice contains pepsin (breaks proteins into polypeptides); pancreatic juice contains pancreatic amylase (starch to disaccharides), pancreatic protease/trypsin (proteins/polypeptides to peptides), pancreatic lipases (lipids to fatty acids and glycerol), and nucleases (DNA/RNA to nucleotides).

What are the specific secretory cells of the gastric mucosa and their functions?

Goblet cells secrete mucus (protects stomach lining); parietal cells secrete gastric acid ($HCl$); chief cells secrete pepsinogen (inactive protease precursor); D cells secrete somatostatin (inhibits acid secretion); and G cells secrete gastrin (stimulates acid secretion).

How are water-soluble nutrients versus fatty acids and glycerol transported away from the small intestine?

Water-soluble nutrients (monosaccharides, amino acids, water-soluble vitamins, minerals) are absorbed directly into blood capillaries and carried via the hepatic portal vein to the liver; fatty acids and glycerol recombine into fats and enter the lacteals (lymph capillaries), which empty into the lymphatic system and eventually into chest veins.

What is the physiological distinction between excretion and elimination in the digestive tract?

Excretion is the removal of metabolic wastes produced by cellular reactions (e.g., urea, carbon dioxide, and bile pigments in feces); elimination (defecation) is the expulsion of undigested, unabsorbed food material (such as cellulose and bacteria) that never took part in cellular metabolism.

What are the primary volumes and percentage components of human blood?

Average blood volume is $4\text{ to }5\text{ litres}$ in females and $5\text{ to }6\text{ litres}$ in males; plasma accounts for $55\%$ of volume ($91\%$ water, $9\%$ dissolved nutrients, ions, gases, hormones, proteins, and wastes), and formed elements make up $45\%$ (erythrocytes, leucocytes, thrombocytes).

In what specific proportions are oxygen and carbon dioxide transported in human blood?

Oxygen is transported as $97\%$ oxyhaemoglobin ($\text{HbO}_2$) and $3\%$ dissolved in plasma. Carbon dioxide is transported as $70\%$ bicarbonate ions ($\text{HCO}_3^-$), $22\%$ carbaminohaemoglobin ($\text{HbNHCOOH}$), and $8\%$ dissolved in plasma.

What sequence of phases and specific timings constitute a single $0.8\text{-second}$ cardiac cycle?

Atrial systole lasts for $0.1\text{ s}$ (atria contract, ventricles in diastole); ventricular systole lasts for $0.3\text{ s}$ (ventricles contract, atria in diastole); and atrial and ventricular diastole lasts for the remaining $0.4\text{ s}$ (both chambers relaxed and filling).

What formula defines cardiac output, and what are its components?

$\text{Cardiac output (mL/min)} = \text{stroke volume (mL)} \times \text{heart rate (beats/min)}$.

What structural differences exist between arteries and veins?

Arteries carry blood away from the heart, possess thick, muscular, elastic walls (a well-developed tunica media), have a smaller lumen, withstand fluctuating high blood pressure, and lack valves; veins carry blood toward the heart, have thinner, less muscular walls with little elasticity, possess a larger lumen, experience low pressure, and contain valves to prevent backflow.

What are the clinical applications of the blood transfusion components: whole blood, red cell concentrates, platelet concentrates, plasma, and cryoprecipitate?

Whole blood is transfused in severe blood loss; red cell concentrates treat anaemia or increase oxygen carrying capacity; platelet concentrates treat abnormal or reduced platelet counts; plasma is administered to patients needing extra clotting factors or with severe liver disease; and cryoprecipitate is used to supply concentrated blood-clotting factors.

What are the functions of lysosomes and peroxisomes in human cells?

Lysosomes are membrane-bound spheres ($0.5\text{ to }1.5\,\mu\text{m}$) containing digestive enzymes (amylases, lipases, nucleases, phosphoric acid) that break down foreign material and worn-out organelles; peroxisomes contain a crystalline core with oxidative enzymes that detoxify harmful and toxic substances, particularly in the liver and kidneys.

Why is the surface area-to-volume ($\text{SA:V}$) ratio a limiting factor in cell size?

As a cell grows, its volume increases as the cube of its dimensions while its surface area increases only as the square; if cell diameter doubles, volume increases eightfold while surface area increases only fourfold, eventually leaving insufficient surface area to support the metabolic exchange needs of the internal volume.

What are the three structural types of cartilage and where are they located in the body?

Hyaline cartilage (thin collagen fibers; located on articular joint surfaces, trachea, bronchi, embryonic skeleton); fibrocartilage (thick collagen bundles withstanding pressure; located in intervertebral discs, knee menisci, pubic symphysis); and elastic cartilage (elastin fibers giving high flexibility; located in external ear auricle, epiglottis).

What type of synovial joint movement is represented by this mechanical diagram?

A ball-and-socket joint, which permits multiaxial movement including complete rotational circumduction in almost any direction (e.g., shoulder and hip joints).

What defines the sliding filament model of skeletal muscle contraction at the sarcomere level?

Thin actin filaments slide past thick myosin filaments toward the center of the sarcomere; the length of the actin and myosin filaments does not change, but the Z lines move closer together, narrowing the I band and H zone while the A band remains constant.

What roles do calcium ions ($Ca^{2+}$), troponin, and tropomyosin play in muscle contraction?

In relaxed muscle, tropomyosin blocks the myosin-binding sites on actin. When $Ca^{2+}$ is released, it binds to subunit TnC of the troponin complex, causing TnI and TnT to undergo a conformational shift that pulls tropomyosin away, exposing the myosin-binding sites on actin.

In muscular control, what are the distinct roles of agonists, antagonists, synergists, and fixators?

The agonist (prime mover) contracts to produce the desired action; the antagonist yields and relaxes or produces the opposite action; synergists assist the agonist by adding extra force or preventing unwanted movement; and fixators specifically immobilize a bone or joint origin to provide a stable base.

What histological and behavioural traits differentiate benign tumours from malignant tumours?

Benign tumours are encapsulated, slow-growing, unable to invade surrounding tissues or vessels, non-metastatic, and usually non-fatal if removed; malignant tumours are unencapsulated, fast-growing, invade nearby tissues, metastasize via blood or lymph to form secondary tumours, and contain poorly differentiated cells.

How does Boyle's law ($PV = k$) govern the mechanics of inhalation and exhalation?

Boyle's law states pressure and volume are inversely proportional. During inspiration, the diaphragm flattens and intercostal muscles lift the ribs, increasing thoracic volume and decreasing alveolar pressure below atmospheric pressure, causing air to rush in; during expiration, muscles relax, decreasing volume and increasing pressure above atmospheric pressure, pushing air out.

What pathogen causes chlamydia, and what clinical complications can arise in untreated women?

Chlamydia is caused by the obligate intracellular bacterium Chlamydia trachomatis; in women, untreated asymptomatic infections can ascend to cause Pelvic Inflammatory Disease (PID), resulting in fallopian tube scarring, ectopic pregnancy, and permanent infertility.

Which pathogen causes syphilis, and what are the clinical characteristics of its three stages?

Treponema pallidum (a spiral spirochaete bacterium). Stage 1 presents with an infectious painless chancre at the site of infection; Stage 2 features skin rashes and prolonged flu-like symptoms followed by a latent period; Stage 3 causes destructive lesions attacking bones, cardiovascular system, and central nervous system (neurosyphilis), leading to insanity and death.

What are the three primary embryonic germ layers, and which major tissues originate from each?

Ectoderm gives rise to epidermis, skin derivatives, and the entire nervous system; mesoderm produces skeletal, smooth, and cardiac muscle, bone, cartilage, blood, connective tissues, and urogenital organs; endoderm gives rise to the epithelial lining of the alimentary canal, respiratory tract, urinary bladder, liver, and pancreas.

What distinct developmental stages occur from day 1 to day 7 post-fertilisation?

Day 1: fertilisation forms the zygote; Days 2–3: cleavage divisions form a solid ball of cells called the morula; Days 4–5: cavitation and differentiation create the hollow blastocyst (composed of trophoblast and inner cell mass); Day 6: zona hatching; Day 7: implantation into the uterine endometrium begins.

What are the definitions of totipotent, pluripotent, and multipotent stem cells?

Totipotent cells can give rise to all cell types of the body plus extraembryonic membranes and placenta (e.g., early zygote); pluripotent cells can give rise to all body cell types but not extraembryonic membranes (e.g., inner cell mass); multipotent cells can differentiate into only a limited range of specialized cell types within a specific tissue lineage (e.g., adult bone marrow stem cells).

What prenatal diagnostic procedure is depicted in this four-step diagram?

Amniocentesis, in which an ultrasound-guided needle withdraws $10\text{ to }20\,\text{mL}$ of amniotic fluid containing foetal cells between weeks $15\text{ and }19$ for chemical, DNA, and chromosomal karyotype analysis.

What are the three critical circulatory shunts present in the foetus that close at birth?

The ductus venosus (shunts umbilical vein blood past the liver to the inferior vena cava), the foramen ovale (shunts blood from right atrium directly to left atrium), and the ductus arteriosus (shunts blood from pulmonary artery directly to aorta, bypassing the lungs).

What triggers the maternal milk let-down reflex during lactation?

Suckling sends sensory nerve impulses from the nipple to the hypothalamus, which stimulates the posterior pituitary gland to secrete oxytocin into the blood; oxytocin causes contraction of the tiny myoepithelial cells surrounding the mammary lobules, forcing milk into the ducts.

How do histone acetyltransferases (HAT) and histone deacetylases (HDAC) alter gene transcription, and how is this imbalanced in tumour cells?

HAT adds acetyl groups ($\text{CH}_3\text{CO}$) to histones, neutralizing positive charges and loosening chromatin to allow transcription factor binding (gene activation); HDAC removes acetyl groups, condensing chromatin and silencing transcription. In tumour cells, overactive HDAC silences tumour suppressor genes (such as $p21$ and $p27$), promoting unchecked growth.

Why do the two genetically identical Agouti mice shown here display completely different coat colours and body sizes?

Due to epigenetic DNA methylation: when the mother's diet is supplemented with methyl donors (folic acid and vitamin $B_{12}$), the agouti gene is methylated and silenced, resulting in lean brown mice; under an unsupplemented normal diet, the agouti gene remains unmethylated and active, resulting in obese yellow mice.

How do combined oral contraceptive pills prevent pregnancy compared to progesterone-only mini pills?

Combined pills contain both oestrogen and progesterone, which inhibit pituitary release of $FSH$ and $LH$ and thereby prevent ovulation; progesterone-only mini pills primarily thicken the cervical mucus to form a sperm-impenetrable plug and alter the endometrial lining to prevent implantation.

What chemical process occurs during deamination in the liver?

Deamination is the enzymatic removal of the amino group ($\text{NH}_2$) from excess amino acids: $\text{Amino acid} + \text{oxygen} \rightarrow \text{ammonia} + \text{organic compounds}$; toxic ammonia is then rapidly converted: $\text{Ammonia} + \text{CO}_2 + \text{energy} \rightarrow \text{urea (H}_2\text{NCONH}_2) + \text{water}$.

What structure is identified here as the site of glomerular filtration within the nephron?

The renal corpuscle, consisting of the glomerulus (capillary knot) enclosed by Bowman's capsule, where high hydrostatic blood pressure drives fluid filtration into the proximal convoluted tubule.

What substances undergo active tubular secretion from the peritubular capillaries into the renal tubules?

Hydrogen ions ($H^+$), ammonium ions ($\text{NH}_4^+$), creatinine, toxins, drugs (such as penicillin), and neurotransmitters are actively secreted into the proximal and distal convoluted tubules.

What are the four phases of the cell cycle and the specific events of interphase?

The cell cycle consists of $G_1$ (first growth), $S$ (DNA synthesis/replication), $G_2$ (second growth/preparation), and $M$ phase (mitosis). During interphase ($G_1, S, G_2$), the cell grows, synthesizes proteins, replicates organelles, and duplicates its DNA.

What is the medical definition of infertility, and what proportion of couples does it affect in Australia?

Infertility is the inability to achieve pregnancy after at least one year of regular, unprotected sexual intercourse; it affects approximately one in six couples in Australia ($40\%$ male factors, $40\%$ female factors, $20\%$ combined).

What is the procedural difference between Gamete Intra-Fallopian Transfer (GIFT) and In Vitro Fertilisation (IVF)?

In GIFT, harvested eggs and sperm are mixed in the laboratory and immediately injected into the fallopian tubes so fertilisation occurs naturally inside the body; in IVF, fertilisation and early embryonic development occur outside the body in culture dishes for $2\text{ to }6\text{ days}$ before an embryo is transferred into the uterus via catheter.

What model of enzyme-substrate interaction is shown in this diagram?

The lock-and-key model, where the active site of the enzyme ($E$) has a rigid, complementary shape that precisely fits the substrate ($S$) to form an enzyme-substrate complex and release products ($P_1, P_2$).

How much ATP is generated per glucose molecule across the stages of cellular respiration?

Up to $38\,\text{ATP}$ total: $2\,\text{ATP}$ from glycolysis (cytosol), $2\,\text{ATP}$ from the Krebs/citric acid cycle (mitochondrial matrix), and up to $34\,\text{ATP}$ from the electron transport chain (mitochondrial cristae).

How does the hydrogen bonding pattern differ between complementary base pairs in DNA?

Adenine and Thymine ($A-T$) are paired by $2$ hydrogen bonds, whereas Cytosine and Guanine ($C-G$) are paired by $3$ hydrogen bonds.

How do complete dominance, incomplete dominance, and co-dominance differ in heterozygous expression?

In complete dominance, the heterozygote exhibits the dominant phenotype identical to homozygous dominant; in incomplete dominance, the heterozygote shows an intermediate blended phenotype (e.g., pink snapdragons from red and white); in co-dominance, both alleles are fully and simultaneously expressed without blending (e.g., roan cattle coat, AB blood group).

Why is blood type O considered the universal red cell donor, and blood type AB the universal plasma donor?

Type O red blood cells express neither A nor B surface antigens, so recipient antibodies will not agglutinate them; Type AB blood plasma contains neither anti-A nor anti-B antibodies, so it cannot agglutinate a recipient's red blood cells.

Why are X-linked recessive disorders such as haemophilia and red-green colour blindness more common in males than females?

Males have only one X chromosome (hemizygous, $X^h Y$); if they inherit a defective allele on the X chromosome, they lack a second X allele to mask it and will express the trait. Females require two copies ($X^h X^h$) to express the disorder; with one copy ($X^H X^h$), they are asymptomatic carriers.

What is Vitamin D-resistant rickets, and how does its inheritance pattern operate?

It is an X-linked dominant condition caused by a mutation in the phosphate-regulating endopeptidase gene that leads to hypophosphatemia and bone softening. Because it is dominant, an affected father will pass the condition to all of his daughters but none of his sons.