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Overview

🌳 Concept tree

Lesson 2→Adrenal Glands, The Pancreas and Reproductive Gonads

├── The adrenal (suprarenal) glands

├── Hormones of the cortex (steroids; controlled by ACTH)
├── Hormones of the medulla (amino-acid derivatives; controlled by nerves)

├── The pancreas as a mixed gland

├── Insulin

├── Glucagon

├── Diabetes mellitus (hyposecretion of insulin)

├── The sex glands (gonads)

├── Male sex hormones — androgens

├── Female sex hormones

├── Gastrointestinal hormones

├── Comparison between nervous and hormonal co-ordination

├── Summary table of the endocrine glands

├── Key terms

├── Negative feedback — the idea behind every endocrine gland

├── Antagonistic pairs

├── Hormones that are linked to the hypothalamus

├── Additional worked examples

└── Typical exam checklists

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The adrenal (suprarenal) glands

Position:

two glands, each lying above one kidney.
Each has two regions that differ in structure and function the outer cortex and the inner medulla.

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Hormones of the cortex (steroids; controlled by ACTH)

Comparison aspect	Main idea	Keywords
Glucocorticoids	(cortisone corticosterone cortisol): regulate carbohydrate metabolism (raise blood glucose by converting proteins and fats into glucose) reduce inflammation and help the body resist stress	cortisonecorticosteronecortisolregulate
Mineralocorticoids	(aldosterone): regulate the mineral balance — increase the reabsorption of sodium and the excretion of excess potassium in the kidney (and so water and blood pressure)	aldosteroneregulatebalanceincrease
Sex hormones	testosterone (male) and oestrogen and progesterone (female). The main source is the gonads but a small amount comes from the adrenal cortex. A tumour of the adrenal cortex or any condition causing excess sex hormones leads to masculinisation of females (beard deep voice) feminisation of males and atrophy (shrinking) of the gonads in both sexes	testosteronemaleoestrogenprogesterone

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Hormones of the medulla (amino-acid derivatives; controlled by nerves)

Adrenaline and noradrenaline

— the "emergency hormones" ("fight, flight or fright").
They prepare the body for emergencies such as fear, anger, excitement and muscular exercise:

raise blood glucose by breaking down liver glycogen to glucose;
increase the speed and force of the heartbeat and raise blood pressure;
increase breathing rate and oxygen consumption, dilate the vessels of muscles and constrict those of the skin and gut;
as a result the muscles obtain the energy and oxygen they need for contraction.

✍️ Worked examples

Worked example 8.
A student jumps at a sudden loud noise his heart pounds, mouth goes dry, and he is pale.
Which hormone and why?
Adrenaline from the adrenal medulla more blood and glucose go to the muscles, while skin vessels constrict (pallor).

Point	Adrenal cortex	Adrenal medulla
Position	Outer	Inner
Hormones	Glucocorticoids mineralocorticoids sex hormones	Adrenaline, noradrenaline
Chemical nature	Steroids	Amino-acid derivatives
Control	ACTH from pituitary	Nervous (sympathetic) stimulation
Importance	Long-term balance of sugar and minerals	Immediate response to emergencies

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The pancreas as a mixed gland

Comparison aspect	Main idea	Keywords
Exocrine	the acini secrete pancreatic juice (digestive enzymes) through the pancreatic duct to the duodenum	acinisecretepancreaticjuice
Endocrine	groups of cells scattered in it the islets of Langerhans secrete hormones directly into the blood. They contain two main types of cells: Alpha (α) cells — few in number — secrete glucagon. Beta (β) cells — the majority — secrete insulin. The two hormones regulate blood glucose and keep it constant at about 80–120 mg per 100 cm³ of blood	groupscellsscatteredislets

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Insulin

It lowers blood glucose:

It allows glucose and other monosaccharides (except fructose) to enter the cells through the membrane, where they are oxidised and used.
It stimulates the cells to oxidise glucose in respiration.
It stimulates the conversion of glucose into glycogen (in liver and muscles) and into fat (lipids) for storage.

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Glucagon

It raises blood glucose by stimulating the conversion of glycogen into glucose in the liver only (muscle glycogen cannot give glucose to the blood).
It is antagonistic to insulin.
Negative feedback:

After a meal, blood glucose rises → β cells release insulin → glucose enters cells and is stored → blood glucose falls to normal.
During fasting or exercise, blood glucose falls → α cells release glucagon → liver glycogen is converted to glucose → blood glucose rises.

Point	Insulin	Glucagon
Cells	Beta cells	Alpha cells
Effect on blood glucose	Decreases	Increases
Effect on glycogen	Glucose → glycogen (and lipids)	Glycogen → glucose
Where	Liver, muscles and other tissues	Liver only
Stimulus	High blood glucose	Low blood glucose
Chemical nature	Protein (polypeptide)	Protein (polypeptide)

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Diabetes mellitus (hyposecretion of insulin)

Low insulin disturbs the metabolism of carbohydrates and lipids. Because glucose cannot enter the cells:

blood glucose rises (hyperglycaemia);
the kidney cannot reabsorb all the glucose, so glucose appears in the urine (glucosuria);
the glucose in the urine holds a lot of water with it (osmotically), so a large volume of urine is excreted (polyuria) → continual thirst (polydipsia);
cells that cannot use glucose burn fats and proteins → weight loss, tiredness, and acidic ketone bodies in the blood; in severe, untreated cases the person falls into diabetic coma.
Treatment: regular insulin injections (type 1), diet and exercise, and tablets that stimulate insulin release (type 2).
Hypoglycaemia (too much insulin or too little food) causes sweating, shaking and fainting; the person is helped by sugar, and in severe cases by glucagon.

Comparison aspect	Main idea	Keywords
Worked example 9 (glucose test).	A fasting person’s blood glucose is 70 mg/100 cm³ — slightly low and glucagon is released. After a heavy meal it rises to 160 → insulin is released → it falls back to about 100	fastingpersonbloodslightly
Another	blood glucose 250 mg/100 cm³ after fasting with glucose in the urine and excessive thirst → diabetes mellitus	bloodglucoseafterfasting
Worked example 10.	A body has 5 litres of blood and a normal level of 100 mg/100 cm³. How much glucose is in the blood? 5000 cm³ ÷ 100 × 100 mg = 5000 mg = 5 g. This small amount (about a teaspoon) shows how precisely it must be regulated	bodylitresbloodnormal

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The sex glands (gonads)

Besides making gametes, the gonads make sex hormones (steroids) for the growth of the genital organs and the appearance of secondary sexual characters at puberty.

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Male sex hormones — androgens

Secreted by the interstitial cells (Leydig cells) of the testes: testosterone and androsterone.
Responsible for growth of the prostate gland and seminal vesicles and other genital organs; secondary male characters (deep voice, facial and body hair, muscular growth, broad shoulders); and (with FSH) sperm production.

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Female sex hormones

Comparison aspect	Main idea	Example	Keywords
Oestrogen (oestradiol)	secreted from the Graafian follicle the corpus luteum and the placenta. It causes the female secondary sexual characters (	breast development wider pelvis) regulates the menstrual cycle and rebuilds the uterine lining (endometrium) after menstruation	secretedGraafianfolliclecorpus
Progesterone	from the corpus luteum and the placenta. Important in pregnancy: it regulates the blood supply of the uterine wall and prepares it to receive the embryo and it brings about the changes of the mammary glands during pregnancy. It also inhibits ovulation (basis of the contraceptive pill)	—	corpusluteumplacentaImportant
Relaxin	secreted by the placenta and uterus at the end of pregnancy it relaxes the pubic symphysis and the ligaments of the pelvis easing delivery	—	secretedplacentauteruspregnancy

(The full hormonal control of the menstrual cycle is explained in Chapter 3.)

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Gastrointestinal hormones

The mucous membrane lining the alimentary canal is both exocrine (digestive juices) and endocrine:

Comparison aspect	Main idea	Keywords
Gastrin	secreted by the stomach wall carried by blood back to the stomach glands stimulating further secretion of gastric juice	secretedstomachwallcarried
Secretin	secreted by the lining of the small intestine (duodenum) stimulates the pancreas to secrete pancreatic juice (rich in bicarbonate)	secretedliningsmallintestine
Cholecystokinin (CCK)	also from the intestinal lining stimulates the pancreas to secrete enzymes and makes the gall bladder contract to release bile into the duodenum	intestinalliningstimulatespancreas

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Comparison between nervous and hormonal co-ordination

Point	Nervous	Hormonal
Messenger	Electrical impulse, transmitter at synapses	Chemical hormone in blood
Path	Along neurons (nerves)	By the blood stream
Speed	Very fast (milliseconds)	Slower (seconds to hours)
Duration of effect	Short, stops quickly	Longer lasting
Target	Specific muscles or glands	Wide, many cells with receptors
Control of	Quick actions, reflexes, movement	Growth, metabolism, reproduction, homeostasis

Why is nervous regulation faster than hormonal?→The impulse travels along nerve fibres at up to 100 m/s and is sent directly to its target, but a hormone must be secreted into the blood, circulated and then bind to receptors.

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Summary table of the endocrine glands

Gland	Hormone	Main action	Hypo / hyper
Anterior pituitary	GH	Growth	Dwarfism / gigantism, acromegaly
	TSH, ACTH, FSH, LH	Stimulate other glands
	Prolactin	Milk production
Posterior pituitary	ADH	Water reabsorption in kidney	Diabetes insipidus
	Oxytocin	Uterine contraction, milk release
Thyroid	Thyroxine	Growth, BMR	Goitre cretinism myxoedema / exophthalmic goitre
	Calcitonin	Lowers blood Ca
Parathyroid	Parathormone	Raises blood Ca	Tetany / fragile bones
Adrenal cortex	Cortisol, aldosterone, sex hormones	Sugar, minerals, sex	Masculinisation etc.
Adrenal medulla	Adrenaline, noradrenaline	Emergency response
Pancreas (islets)	Insulin / glucagon	Lowers / raises blood glucose	Diabetes mellitus
Testes / ovaries	Androgens / oestrogen, progesterone	Secondary sex characters
Stomach, intestine	Gastrin, secretin, CCK	Digestive secretions

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Key terms

Hormone; endocrine; exocrine; mixed gland; target organ; master gland; adenohypophysis; neurohypophysis; hypothalamus; gigantism; dwarfism; acromegaly; ADH; oxytocin; thyroxine; goitre; cretinism; myxoedema; parathormone; calcitonin; cortex; medulla; glucocorticoid; aldosterone; adrenaline; islets of Langerhans; insulin; glucagon; diabetes mellitus; androgen; oestrogen; progesterone; relaxin; gastrin; secretin; cholecystokinin; auxin.

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Negative feedback — the idea behind every endocrine gland

Most hormones are controlled by negative feedback→the effect produced by the hormone switches off (or reduces) the secretion of that same hormone, which prevents over- and under-secretion.

Comparison aspect	Main idea	Keywords
Thyroid	hypothalamus → pituitary releases TSH → thyroid releases thyroxine → rising thyroxine in blood inhibits the pituitary (TSH falls) → thyroxine falls. When thyroxine is low (iodine deficiency) the inhibition is lost TSH keeps rising and the gland enlarges: simple goitre	hypothalamuspituitaryreleasesthyroxine
Blood calcium	low Ca²⁺ → parathormone ↑ (calcitonin ↓) → Ca²⁺ rises → parathormone falls. High Ca²⁺ → calcitonin ↑ → Ca²⁺ falls	parathormonecalcitoninrisesfalls
Blood glucose	high → insulin ↑ glucagon ↓ low → glucagon ↑ insulin ↓	highinsulinglucagon
Sex hormones	oestrogen and progesterone from the ovary inhibit FSH and LH (this is why the contraceptive pill stops ovulation)	oestrogenprogesteroneovaryinhibit

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Antagonistic pairs

Pair	Effect of the first	Effect of the second
Insulin / glucagon	Lowers blood glucose	Raises blood glucose
Parathormone / calcitonin	Raises blood calcium	Lowers blood calcium
Aldosterone / (ADH balance)	Retains Na⁺, loses K⁺	ADH retains water

Insulin and glucagon act on blood glucose in opposite directions.
Insulin lowers blood glucose by acting on the liver, muscle and fat cells.
Glucagon raises it by acting on the liver only, because muscle cells lack the enzyme glucose-6-phosphatase and cannot release their glycogen as free glucose into the blood.
Aldosterone acts on the kidney tubules: it increases sodium reabsorption and speeds up potassium excretion.

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Hormones that are linked to the hypothalamus

The hypothalamus makes releasing hormones for the anterior lobe and makes ADH and oxytocin itself (stored in the posterior lobe).
It is therefore the real "coordinating centre" between the nervous and endocrine systems, receiving information on temperature, blood concentration and emotions.

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Additional worked examples

✍️ Worked examples

Worked example 11 (reading symptoms).
A patient has a fasting blood glucose of 260 mg/100 cm³, passes a large volume of urine which tastes sweet, and drinks heavily.
The cause is insulin deficiency (diabetes mellitus) glucose cannot enter cells, so blood glucose rises above the kidney threshold, glucose appears in urine and takes water with it.
The patient is treated with insulin.
Worked example 12 (cause and effect chain).
A woman with a tumour of the adrenal cortex develops a deep voice and facial hair.
Explain the tumour secretes too much androgen-like sex hormone, causing masculinisation; the excess hormone also inhibits the pituitary’s gonadotrophins, so the ovaries shrink (atrophy).

Worked example 13 (comparing two diseases that have similar names).
Diabetes mellitus — insulin deficiency, high blood glucose, glucose in urine.
Diabetes insipidus — ADH deficiency, large volume of dilute urine, no excess glucose.
Both cause great thirst.
Worked example 14 (experimental reasoning).
A tadpole fed with thyroid extract metamorphoses into a tiny frog early; a tadpole whose thyroid is removed remains a tadpole.
Conclusion thyroxine controls metamorphosis and growth (thyroxine stimulates metabolism).

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Typical exam checklists

Comparison aspect	Main idea	Keywords
Hypo/hypersecretion questions	always state the hormone the gland the age of the patient (child/adult) and the symptoms	alwaysstatehormonegland
Give reason questions	"Pituitary is the master gland because it controls the secretion of the thyroid adrenal cortex and gonads through its trophic hormones."	Pituitarymasterglandbecause
Pancreas is a mixed gland because	the acini secrete juice through a duct (exocrine) and the islets secrete insulin and glucagon directly into blood (endocrine)	acinisecretejuicethrough
Diabetic patients feel thirsty because	glucose in the urine draws water out with it (osmosis) causing loss of water in large volumes of urine	glucoseurinedrawswater
Some diabetic patients fall into coma because	untreated insulin shortage causes extreme hyperglycaemia and acid ketone bodies in the blood if too much insulin is injected severe hypoglycaemia deprives the brain of glucose	untreatedinsulinshortagecauses
Adrenaline prepares the body for emergencies	by raising blood glucose (from liver glycogen) heart rate blood pressure and oxygen supply to the muscles	raisingbloodglucoseliver
Nervous regulation is faster than hormonal	because nerve impulses are transmitted directly along nerve fibres at high speed while hormones must be released into the blood and carried to the target organs	becausenerveimpulsestransmitted

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Part 21

📖

🔍 In-Depth Explanations, Deductions & Multi-Book Insights:

DABOUR HUB ACADEMY • EGYPTIAN HIGH SCHOOL (THANAWEYA AMMA)
EXPLANATION Lesson 2: Adrenal Glands, The Pancreas and Reproductive Gonads
Course Biology (Senior 3) | Chapter 2 – Hormonal Coordination in Living Organisms | Official Ministerial Syllabus 2026/2027
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1. Academic Lesson Overview & Pedagogical Objectives

The adrenal glands regulate stress and minerals (Cortex vs Medulla)
the pancreas governs blood glucose through insulin and glucagon
and gonadal sex hormones drive primary and secondary sexual characteristics.

2. Hierarchy Classification Tree (Cognitive Concept Map)

Below is the hierarchical structural tree organizing the conceptual core of this lesson:

Metabolic and Stress Hormones

├── 1. Adrenal Glands (Suprarenal)

│ ├── Adrenal Cortex (Steroids via ACTH)Glucocorticoids (Cortisone), Mineralocorticoids (Aldosterone), Sex Steroids

│ └── Adrenal Medulla (Fight or Flight via Sympathetic)Adrenaline & Noradrenaline

├── 2. Endocrine Pancreas (Islets of Langerhans)

│ ├── Alpha CellsGlucagon (Raises blood glucose by glycogenolysis in liver)

│ └── Beta CellsInsulin (Lowers blood glucose by cellular uptake & glycogenesis)

└── 3. Gonads (Sex Hormones)

├── Male (Testes)Testosterone & Androsterone (Interstitial cells)

└── Female (Ovaries)Estrogen (Graafian follicle), Progesterone (Corpus luteum), Relaxin

3. The Master Teacher's Blackboard & Exam Rules

Comparison aspect	Main idea	Keywords
•	Extracted high-yield rules golden equations and trap warnings from top Egyptian teachers	Extractedhighyieldrules
• RULE 1	Glucose Antagonism: Insulin LOWERS blood glucose (target: liver muscle adipose) Glucagon RAISES blood glucose (target: LIVER ONLY does not act on muscle glycogen!)	GlucoseAntagonismInsulinLOWERS
• RULE 2	Aldosterone increases renal Na+ reabsorption and accelerates K+ excretion	Aldosteroneincreasesrenalreabsorption
• RULE 3	Adrenaline rapidly elevates blood glucose increases heart rate and dilates skeletal muscle vessels during emergencies	Adrenalinerapidlyelevatesblood
• TRAP	Glycogen in muscles cannot be converted directly into blood glucose by glucagon because muscle lacks glucose-6-phosphatase	Glycogenmusclescannotconverted

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Curriculum

Biology & Geology

Chapter 1 - Support and Movement in Living Organisms

Chapter 2 - Hormonal Coordination in Living Organisms

Chapter 3 - Reproduction in Living Organisms

Chapter 4 - Immunity in Living Organisms

Chapter 5 - Molecular Biology - DNA Structure and Function

Chapter 6 - Molecular Biology - RNA, Protein Synthesis and Genetic Engineering

Chapter 7 - Geology, Earth Sciences and Ecology

Lesson 2: Adrenal Glands, The Pancreas and Reproductive Gonads

🌳 Concept tree

├── The adrenal (suprarenal) glands

├── The pancreas as a mixed gland

├── Insulin

├── Glucagon

├── Diabetes mellitus (hyposecretion of insulin)

├── The sex glands (gonads)

├── Male sex hormones — androgens

├── Female sex hormones

├── Gastrointestinal hormones

├── Summary table of the endocrine glands

├── Key terms

├── Antagonistic pairs

├── Hormones that are linked to the hypothalamus

├── Additional worked examples

└── Typical exam checklists

✍️ Worked examples

✍️ Worked examples

🔍 In-Depth Explanations, Deductions & Multi-Book Insights:

1. Academic Lesson Overview & Pedagogical Objectives

2. Hierarchy Classification Tree (Cognitive Concept Map)

Metabolic and Stress Hormones

3. The Master Teacher's Blackboard & Exam Rules

Well done! You finished this lesson