7.7: Alternate Text Descriptions

Figure 7.1: Human Ovary

This is an image of a histological section of a human ovary (Follicle Development Stages):

• Label 1: Primary follicle
  • Contains a growing oocyte
  • Surrounded by one to a few layers of cuboidal granulosa cells
• Label 2: Early secondary follicle
  • Shows multiple layers of granulosa cells
  • Small fluid-filled spaces begin forming within the follicle
• Label 3: Tertiary (Graafian) follicle
  • Characterized by a large fluid-filled antrum
  • Oocyte sits on a mound of cells called the cumulus oophorus
  • Has a well-defined thecal layer surrounding the follicle
• Label 4: Primordial follicle
  • Located in the ovarian cortex
  • Contains a small oocyte
  • Surrounded by a single layer of flattened follicular cells

Figure 7.1.1: Testicular Reproductive System

This image is a three-part illustration showing the location of the male reproductive system, the appearance of uncircumcised and circumcised penises, and a lateral view of the internal reproductive structures.

Figure 7.1.2: Scrotum and Testes: External, Muscular, and Deep Anatomy

This three-panel horizontal diagram illustrates the progressive anatomical layers of the human scrotum and testes, moving from the external surface on the left, through the superficial muscle layers in the middle, to the deep internal tissues and spermatic cords on the right.

Figure 7.1.3: Anatomy of the Testis and Epididymis

This figure shows a cross-sectional view of the testis and the pathway sperm follow as they are produced, collected, matured, and transported out of the testis.

The testis occupies the center of the image and is enclosed within the scrotum, a pouch located outside the body. Surrounding the testis are two protective layers. The outer layer is the tunica vaginalis, and the deeper, thicker tunica albuginea forms a strong fibrous capsule around the testis.

Extensions of the tunica albuginea project inward as septa, dividing the testis into multiple compartments called lobules. Within each lobule are tightly coiled seminiferous tubules, where sperm are produced. Their coiled arrangement increases the surface area available for spermatogenesis.

The seminiferous tubules converge into straight tubules, which carry newly formed sperm toward the center of the testis. The straight tubules empty into the rete testis, a network of interconnected channels near the posterior region of the testis. The rete testis collects sperm from many seminiferous tubules and directs them toward the next stage of transport.

From the rete testis, sperm enter several efferent ductules, which pass out of the testis and into the head of the epididymis. The epididymis lies along the posterior and superior surface of the testis and is divided into a head, body, and tail. As sperm travel through the highly coiled duct of the epididymis, they mature and acquire the ability to move and fertilize an egg.

At the inferior end of the epididymis, the tail of the epididymis narrows and continues as the ductus (vas) deferens. The ductus deferens extends upward from the scrotum into the spermatic cord, which contains the vessels, nerves, and ducts that connect the testis to the body. The spermatic cord ascends through the inguinal canal, shown at the top of the figure.

Surrounding the spermatic cord and testis is the cremaster muscle. This muscle raises or lowers the testes to help regulate temperature. Maintaining the testes slightly cooler than core body temperature is important for normal sperm production.

The figure demonstrates the organization of the testis and the pathway of sperm transport. Sperm are produced within the seminiferous tubules, collected by the straight tubules and rete testis, carried through the efferent ductules into the epididymis for maturation, and then transported into the ductus deferens. The surrounding tunics, septa, scrotum, spermatic cord, and cremaster muscle provide protection, structural support, and temperature regulation necessary for normal reproductive function.

Figure 7.1.4: Spermatogenesis and Histology of a Seminiferous Tubule

This is a multi‑panel figure that illustrates spermatogenesis and the structure of a seminiferous tubule.

1. Spermatogenesis (left panel) - This schematic shows the stages of sperm development with labeled cell types and chromosome numbers. Arrows indicate progression downward through each stage, showing reduction from diploid to haploid cells.
   • At the top, a cell labeled Spermatogonium (2n) undergoes mitosis to produce more diploid cells.
   • A cell differentiates into a Primary spermatocyte (2n).
   • The primary spermatocyte undergoes Meiosis I to form two Secondary spermatocytes (1n).
   • Each secondary spermatocyte undergoes Meiosis II, producing four Spermatids (1n).
   • Spermatids then undergo Spermiogenesis, developing into mature sperm cells labeled Spermatozoa (sperm), shown with heads and long tails.
2. Cross section of a seminiferous tubule (right panel) - A microscope image shows a circular seminiferous tubule with a central open space labeled Lumen.
   • Cells within the tubule:
     • Near the outer edge are Spermatogonia
     • Moving inward are Primary spermatocytes
     • Closer to the lumen are Early spermatids
     • Supporting cells labeled Sertoli (sustentacular) cells extend across the thickness of the tubule
   • Outer and surrounding structures
     • The area outside the tubule is labeled Interstitial tissue
     • Within this region are Leydig (interstitial) cells, which produce hormones
     • Blood vessels labeled Arteriole and Peritubular capillary
     • A Lymphatic capillary is also identified

Figure 7.1.5: Structure of the Sperm Cells

This image shows the structure of a sperm cell, divided into labeled regions: head, mid‑piece, and tail.

1. Head - The oval-shaped head is outlined and contains internal components:
   • The outer layer is labeled Plasma membrane
   • Beneath it is the Nucleus, which occupies most of the head and contains genetic material
   • At the front tip is the Acrosome, a cap-like structure that contains enzymes used to penetrate the oocyte during fertilization
2. Mid-piece - Just behind the head is a narrow segment labeled Mid‑piece:
   • This region contains a Centriole, which helps organize microtubules
   • Surrounding the central core are many Mitochondria, arranged in a spiral pattern
   • The mitochondria provide energy required for movement
3. Tail - The long, whip-like Tail extends from the mid‑piece:
   • The main structure is labeled Flagellum, which propels the sperm forward
   • Within the tail is an internal support structure labeled Axial filament
   • The tail tapers toward the end
4. End piece - The farthest portion is labeled End piece, representing the thin terminal segment of the tail

Figure 7.1.6: Cross-Sectional Anatomy of the Penis

This image compares the structure and blood flow of the penis in flaccid and erect conditions, using both lateral (side) and transverse (cross‑section) views.

1. Top left: Flaccid – Lateral view. The penis is shown in a relaxed (flaccid) state. The tissue appears relatively less filled with blood, and the structure is soft and curved downward. Internal tissues are labeled:
   • Corpora cavernosa, two columns of erectile tissue
   • Corpus spongiosum, surrounding the urethra
   • Spongy urethra, running through the length of the penis
   • Prepuce (foreskin) covering the distal end
2. Top right: Flaccid – Transverse view. A cross‑section of the penis shows circular arrangement of tissues. The venules are open, indicating normal blood drainage in the flaccid state.
   • Two large areas labeled Corpora cavernosa
   • A smaller area labeled Corpus spongiosum containing the Spongy urethra
3. Blood vessels include:
   • Deep dorsal vein
   • Penile venules (uncompressed)
   • Cavernosal arteries
4. Bottom left: Erect – Lateral view. The penis is shown in the erect state, with labeled steps. The corpora cavernosa are visibly expanded, producing rigidity.
   • “Cavernosal arteries dilate, engorging corporal tissue with blood.”
   • “Engorging causes corporal tissue to swell, erecting the penis.”
5. Bottom right: Erect – Transverse view. The cross‑section shows tissues filled with blood:
   • “Engorged corporal tissue compresses penile veins and venules, maintaining erection.”
   • Structures include:
     • Enlarged Corpora cavernosa
     • Corpus spongiosum still surrounding the urethra
     • Cavernosal arteries delivering blood
     • Compressed Penile veins and venules, reducing blood outflow

Figure 7.1.7: Regulation of Testosterone Production

This image illustrates hormonal regulation of male reproductive function through a feedback loop involving the hypothalamus, pituitary gland, and testes. The diagram is organized into three numbered steps.

1. Step 1: Hypothalamus and pituitary signaling - At the top, the Hypothalamus releases a hormone labeled GnRH (gonadotropin‑releasing hormone). A label states:“Hypothalamus releases GnRH. GnRH stimulates the anterior pituitary to release FSH and LH.” These are shown with colored arrows labeled “FSH release” and “LH release.” Arrows indicate GnRH moving from the hypothalamus to the anterior pituitary, which then releases:
   • FSH (follicle‑stimulating hormone)
   • LH (luteinizing hormone)
2. Step 2: Testicular response - FSH and LH act on the testes. A label states “LH stimulates the Leydig cells to release testosterone. FSH stimulates the Sertoli cells to release ABP. ABP binds to testosterone, keeping the latter at a high concentration.”
   • LH targets Leydig (interstitial) cells, located in the interstitial space between seminiferous tubules, causing testosterone release
   • FSH targets Sertoli cells within the seminiferous tubule, leading to release of androgen‑binding protein (ABP)
   • Arrows connect:
     • Leydig cells → Testosterone release
     • Sertoli cells → Androgen-binding protein (ABP) release
3. Step 3: Negative feedback - A label on the left states “Inhibin negatively feeds back to anterior pituitary, inhibiting further release of FSH. Testosterone negatively feeds back to the hypothalamus and pituitary, inhibiting further release of GnRH, FSH, and LH.” Negative feedback is indicated by arrows marked with a minus sign.
   • Inhibin, released from Sertoli cells, inhibits FSH release from the anterior pituitary
   • Testosterone feeds back to both the hypothalamus and pituitary, reducing production of:
     • GnRH
     • FSH
     • LH

Figure 7.2.1: Human Female Reproductive System: Lateral and Anterior Views

This two-panel illustration presents the human female reproductive system from two anatomical perspectives: a lateral (sagittal/profile) view in the top panel and an anterior (front) view in the bottom panel.

Figure 7.2.2: Vulva: External and Internal Anatomy

This two-panel figure illustrates the anatomy of the female vulva, showing an external anterior view on the left and an internal anterolateral view on the right.

Figure 7.2.3: Oogenesis and Oocyte Development

This image illustrates oogenesis (egg development) and highlights key stages of meiosis, including when the process pauses and resumes.

1. Top section: Early development (before birth) - At the top, a cell labeled Oogonium (2n) undergoes mitosis, producing additional diploid cells. One cell develops into a Primary oocyte (2n). A label indicates “Meiosis I begins.” Another label states: “Meiosis arrests in prophase I.” This indicates that primary oocytes begin meiosis before birth but remain paused. A horizontal line divides the diagram into two time periods:
   • Before birth (above the line)
   • After puberty (below the line)
2. Middle section: After puberty - Below the line labeled After puberty, a label indicates: “Meiosis I resumes.” The polar body may divide further into additional small cells labeled Second polar bodies (n). The primary oocyte completes Meiosis I, producing:
   • One Secondary oocyte (n)
   • One First polar body (n)
3. Inset box: Fertilization-dependent completion - A boxed section highlights key stages related to fertilization:
   • A label states: “Oocyte meiosis arrests at metaphase II.” This shows the secondary oocyte pauses again before fertilization.
   • Another label states: “Oocyte meiosis completes immediately after sperm penetrates the oocyte.”
   • After sperm entry:
     • The secondary oocyte completes Meiosis II
     • A Mature ovum (n) is formed
     • Additional polar bodies (n) are produced

Figure 7.2.4: Folliculogenesis

This image is a multi‑panel figure illustrating (a) the stages of folliculogenesis in the ovary and (b) a histological image of a secondary follicle.

1. Stages of Folliculogenesis Six numbered stages are shown in sequence with arrows indicating progression.
   • Stage 1: Primordial follicle - A small structure contains an oocyte surrounded by cells labeled ovary cortex cells and granulosa cells. The oocyte nucleus is labeled within the center.
   • Stage 2: Primary follicle - The oocyte increases in size and becomes surrounded by multiple layers of granulosa cells. A new layer labeled zona pellucida appears around the oocyte. The oocyte nucleus remains visible.
   • Stage 3: Secondary follicle - The follicle grows larger. Labels include:
     • Granulosa cells surrounding the oocyte
     • Theca cells forming an outer layer
     • Zona pellucida around the oocyte
     • Oocyte and oocyte nucleus
   • Stage 4: Tertiary follicle - A fluid-filled space labeled Antrum appears within the follicle. Additional labels include:
     • Granulosa cells
     • Theca cells
     • Cortex
   • The oocyte, now positioned to one side of the follicle
   • Stage 5: Ovulating follicle - The follicle ruptures at the surface of the ovary. Labels show:
     • Oocyte leaving the follicle
     • Granulosa cells surrounding it
     • A label reading “Ruptured follicle”
   • Stage 6: Corpus luteum - After ovulation, the follicle transforms into the corpus luteum within the ovary. It appears as a folded, glandular structure and continues to function hormonally.
2. Secondary Follicle (microscopic image) - A grayscale histology image shows a cross‑section of a follicle with labeled structures:
   • Oocyte at the center, with labeled Nucleus of oocyte and Nucleolus
   • Surrounding layer of Zona pellucida
   • Cells immediately around the oocyte labeled Corona radiata
   • Larger surrounding layers labeled Granulosa cells
   • Outer layer labeled Theca cells
   • A developing space labeled Developing antrum
   • Surrounding tissue labeled Ovarian stroma
   • A nearby vessel labeled Perifollicular capillary

Figure 7.2.5: Hormonal Regulation of the Ovarian Cycle

This image multi‑panel diagram shows hormonal regulation of the ovarian cycle, divided into three phases: Follicular phase, Ovulation, and Luteal phase. The diagram illustrates interactions among the hypothalamus, anterior pituitary, ovaries, and uterus, along with positive and negative feedback loops.

1. Follicular Phase - At the top, the Hypothalamus releases GnRH (gonadotropin‑releasing hormone), which stimulates the Anterior pituitary. The pituitary releases FSH (follicle‑stimulating hormone) and LH (luteinizing hormone).
   • Arrows show FSH and LH acting on the Ovaries, specifically on Follicles.
   • A label states: “Pituitary hormone effect: LH and FSH stimulate several follicles to grow.”
   • The developing follicles produce estradiol, which has two effects:
     • Negative feedback (shown with a minus sign) on the hypothalamus and pituitary, inhibiting GnRH, FSH, and LH production
     • Stimulation of the Uterus, causing the endometrium to thicken
2. Ovulation - The second panel shows a shift to positive feedback. Estradiol levels increase and now stimulate (shown with a plus sign) the Hypothalamus and the Anterior pituitary. This leads to increased production of GnRH, FSH and LH. A label states: “LH surge triggers ovulation.” The arrows show continued signaling from pituitary to ovaries, leading to the release of an oocyte from a mature follicle.
3. Luteal Phase - After ovulation, the follicle transforms into the Corpus luteum in the Ovaries. The corpus luteum produces progesterone. A label states: “Pituitary hormone effect: LH stimulates formation of a corpus luteum from follicular tissue left behind after ovulation.” Progesterone has the following effects:
   1. Maintains the endometrium of the uterus
   2. Provides negative feedback (minus signs) to the hypothalamus and pituitary, reducing GnRH, FSH and LH
   3. Another label explains: If the corpus luteum degenerates, progesterone declines, leading to shedding of the uterine lining

Figure 7.2.6: Female Reproductive Anatomy and Histology of the Ovary and Uterus

This image is a multi-panel figure showing the anatomy of the female reproductive system together with microscopic images of ovarian and uterine tissues.

Figure 7.2.7: Hormone Levels in Ovarian and Menstrual Cycles

This image is a multi panel diagram that shows the relationship between follicle development, ovarian cycle phases, uterine cycle phases, and hormone levels across a 28‑day menstrual cycle.

1. Top panel: Follicle development and selection (Days 1–7) - At the top, an arrow labeled “Follicular phase Days 1–7” runs from left to right. Three sequences of follicle development are shown:
   • Primordial follicles → Primary follicles → Secondary follicles. Some follicles undergo Atresia (degeneration), while one pathway shows Selection of a dominant follicle. This leads to a single, selected tertiary follicle that will continue development. A label states:
     • “Constant development of early-stage follicles (2 months)”
     • “Selection of one dominant secondary follicle begins each new menstrual cycle”
2. Second panel: Ovarian cycle phases - A timeline labeled “Day of menstrual cycle” runs from 0 to 28 days.
   1. Phases include:
      • Follicular phase (days 0–14)
      • Ovulation (around day 14)
      • Luteal phase (days 14–28)
   2. Structures shown along the timeline:
      • Selected tertiary follicle (before ovulation)
      • Ovulation event at midcycle
      • Corpus luteum (after ovulation)
      • Corpus albicans and Degrading corpus toward the end of the cycle
3. Third panel: Uterine cycle phases
   1. A second timeline labeled “Uterine cycle phases” shows:
      • Menses (Menstruation) at the beginning (days 0–5)
      • Proliferative phase (approximately days 5–14)
      • Secretory phase (approximately days 14–28)
   2. The endometrium (uterine lining) is shown:
      • Shedding during menstruation
      • Thickening during the proliferative phase
      • Becoming more glandular and vascular during the secretory phase
4. Fourth panel: Pituitary hormone levels - Both hormones are plotted over days 0–28.
   1. A graph labeled “Pituitary hormone levels” shows:
      • FSH (follicle‑stimulating hormone)
      • LH (luteinizing hormone)
   2. Key pattern:
      • LH shows a sharp surge at about day 14 (ovulation)
      • FSH shows a smaller increase at midcycle
5. Fifth panel: Ovarian hormone levels
   1. A second graph labeled “Ovarian hormone levels” shows:
      • Estrogen
      • Progesterone
   2. Patterns include:
      • Estrogen rises during the follicular phase and peaks just before ovulation
      • Progesterone rises after ovulation during the luteal phase and then declines before menstruation

Figure 7.2.8: HPV, p53, and Regulation of the Cell Cycle in Cervical Cells

compares normal cell-cycle regulation with the effects of human papillomavirus (HPV) on cervical cells. The figure includes a cell-cycle diagram on the left and two numbered pathways on the right labeled HPV not present and HPV present.

Figure 7.2.9: Mammary Gland: Superficial and Internal Anatomy

This two-panel illustration shows the superficial and internal anatomy of the human mammary gland. The left panel presents a split anterior (front) view, and the right panel presents a sagittal lateral (side) cross-section.

Figure 7.3.1: Hormonal Regulation of Puberty

This image illustrates the hormonal regulation of puberty through the hypothalamus–pituitary–gonadal axis and its effects on male and female reproductive systems.

1. Top section: Hormone initiation - At the top center, the Hypothalamus is shown releasing GnRH (gonadotropin‑releasing hormone). A labeled step states: 1. “Beginning at approximately age 8, the hypothalamus increases its production of gonadotropin‑releasing hormone (GnRH).” Arrows show GnRH moving downward toward the anterior pituitary.
2. Middle section: Pituitary response - A second labeled step states: 2. “GnRH triggers the anterior pituitary to release luteinizing hormone (LH) and follicle‑stimulating hormone (FSH).” Arrows labeled “LH and FSH release” show these hormones traveling from the pituitary to two target organs:
   • Testis (left)
   • Ovary (right)
3. Step 3: Gonadal hormone production - A third labeled step states: 3. “LH and FSH trigger testosterone production in the testes and estrogen production in the ovaries.” Arrows labeled “Testosterone release” and “Estrogen release” extend downward.
   • On the left, the testis releases Testosterone
   • On the right, the ovary releases Estrogen
4. Step 4: Effects of sex hormones - A labeled step states: 4. “Effects of sex hormone release:”
   1. Male outcomes
      • Spermatogenesis begins
      • Male secondary sex characteristics develop, including:
        • Penis and scrotum growth
        • Facial hair growth
        • Larynx elongation (voice lowers)
        • Shoulders broaden
        • Body, armpit, and pubic hair grow
        • Muscle mass increases
   2. Female outcomes
      • Folliculogenesis begins
      • Female secondary sex characteristics develop, including:
        • Breast development and maturation
        • Hip widening
        • Pubic hair growth
5. Step 5: Feedback regulation - A labeled step states: 5. “Before puberty, the hypothalamus and pituitary are very sensitive to negative feedback signals from testosterone and estrogen. During puberty, this sensitivity decreases.” This decreased sensitivity allows increased hormone production, promoting puberty and secondary sex characteristic development. Arrows marked with a minus sign indicate negative feedback from:
   • Testosterone (left pathway)
   • Estrogen (right pathway)